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Render cleaning

Posted on 15 May, 2014 at 16:57 Comments comments ()

Greening render : 
Why and how to control it.

In the past 3 decades or so self finished renders became popular among architects. There are good reasons for this, both architectural and practical. For the designer, new finishes difficult to obtain with paint were offered.  Smooth, textured, with mica sparkles or colour pebbles. They are low maintenance too. Every now and again cleaned, but never painted again. On site, no more curing time before finishing the building. It suits modern building constraints.
However, the cleaning periodicity has reduced from 5 years to 4 and sometime 3 years. The introduction of wall insulation appears to be the prime reason. Broadly, more heat transfer through the wall means a drier render and less microbial growth. The amount of insulation conditions the rapidity of the microbial growth. The position of the insulation within the wall is also instrumental in that if will affect the thermal inertia of
the outer leaf, and it’s behaviour to diurnal cycles.

Architecture is also responsible.
Flush, crisp line facades without shadow gaps at parapet and sills will inevitably lead to microbial disfiguration in a wet climate. Published studies show that a temperature increase of 1 to 2OK leads to decreasing the relative humidity of the render by approximately 10%. The white patches on soiled render correspond to a small variation in the heat transfer across the wall, sometimes revealing the position of the insulation fixings or a radiator. The white patches have stayed cleaner.

Formation & composition of a biofilm.
A biofilm forms when certain microorganisms adhere to a surface in a moist environment and begin to reproduce.
Biofilm formation on surfaces usually starts with phototrophic organisms (algae, cyanobacteria) which use carbon dioxide (CO2) from the atmosphere and sunlight as their carbon and energy source.
Heterotrophic organisms (most bacteria and all fungi) need some organic source for their growth, and this is provided by the metabolites of phototrophic organisms or by air- borne deposition. The biofilm community is therefore sometimes formed by a single microbial species, but in nature biofilms almost always consist of mixtures of many species of bacteria, as well as fungi, algae, yeasts, protozoa, and
other microorganisms, along with non-living debris and corrosion products.

Red algae
The genus would not, at first glance, be taken as a green alga. Free-living species are mostly yellow to bright orange or red-brown in colour, due to the orange pigment, haematochrome ( β‐carotene), which usually hides the green of the chlorophyll. The genus is terrestrial and is often found in
Europe on rocks, walls and tree bark. Where they are found on
buildings, they can cause severe mechanical degradation and
All biofilm forming microorganisms may cause biodeterioration
and degrade stone or render mechanically, chemically and aesthetically through the metabolic activities and biomineralization process in these biofilms. The porosity of the surface, it's mineral composition, alkalinity and it's ability to retain air borne sea salts creates an environment favourable to the settlement of microrganisms.
Trentepholia have been identified as one of the most common
species to be isolated from walls and buildings in Western Ireland

Cleaning a contaminated render.
The straight forward way of controlling the biofilm is by impregnating the
surface with a solution of quaternary ammonium. The product Algoclear
Pro works on the biofilm by puncturing microorganisms cell walls. It does not interact with the mineral components of self finished renders and does not contain any compound deleterious to the colouring agents or
the surface cohesion. In particular, the product has a neutral pH. 
On porous render, the surfactant active will decontaminate deep into the
surface porosity by capillary action.
The reaction to the treatment varies from specie to specie:
Algae - green and red - will die within minutes of the application. If the
algal film is thick enough, a milky sheen will replace it for a short period,
before dispersing in the wind. The orange pigment originating from the
red algae Trentepholia may dwell in the surface porosity, but being water
soluble will wash away with the rain. 10 days is a reasonable prediction.
The treatment is by spray.
Bacteria and cyanobacteria have thin cell walls and die at rates varying
with the concentration of the Algoclear solution. At a normal rate all studied species die within one hour. The self cleansing process takes a few days in normal exposure. The treatment is by spray.
Moulds : They are a group of filamentous fungi. Their structure enable them to key their filaments in the porosity of render and even rock. As a result, moulds do not self cleanse as readily as algae. 
The most common species of fungi on facades are the Cladosporium spp and Alternaria spp. Both metabolise a black pigment protecting them from UV radiations, and causing some staining of the
surface. Moulds are killed by a solution of Algoclear within approximately one hour. The self cleansing however can take several months, or is helped in a second visit by rinsing with fresh water.
The treatment of moulds is best carried out in 3 steps. First remove the thick with a scraper or brush and water until the substrate is clearly visible. Apply a 1/30 solution of Algoclear Pro using a soft bristle brush. This helps softening the biofilm. After brushing, a rapid rinsing with a solution 1/30 Algoclear Pro will complete the second step. About 6 weeks after the treatment the black discolourations should have significantly receded. It will normally wash away naturally but it has been observed in a minority of cases that some rinsing had to take place as a final step.
It must be noted that a key to durability of render cleaning lies in how
clean the water running over it is. If it transports more of the same
cocktail of species, the treatment will not be durable. Care must be taken in thoroughly decontaminating parapet copings, verge overcloak and ideally the roof above.

Rough cast and pebble dash.
Textured surfaces generally catch some grime as well as hosting life. The
best option is to brush a solution 1/30 Algoclear Pro into the surface using a soft brush. The hardness of the bristle is a matter of personal preference between soft and medium soft. Upon brushing an area, it is best to rinse the dirt lifted by the brush from the surface with a solution of Algoclear.
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Aggressive Vs Non aggressive exterior cleaning.

Posted on 11 June, 2013 at 15:40 Comments comments ()
Hi folks!

Guess what? 
Yes, it's raining here Ireland...Give's me a bit of time to add another post here though so not all bad (if only it lasted the twenty mins it took to do this!) 
Another great advantage to this warm wet weather?? The moss and algae love it! 

I was in Ardara, Co. Donegal a couple of weeks back at a training day for applicators of the Mossgo Pro system, Michael Conway who was giving the course had put together a few pages of information and pictures and among these was a table titled Method/Product Comparison, which outlined the Pro's and Con's for both Aggressive (pressure washing, harmful chemical cleaning) and Non aggressive (Mossgo pro system).
What was most interesting about the content was the fact  that a (converted) professional power washer who was also in attendance agreed 100% with everything that was printed!

I'm not saying that pressure washing or chemical cleaning is a completely flawed industry or that everyone in it is out to con people, after all I wouldn't recommend using our system to clean your car or to remove graffiti for instance. But if people were more educated to the Pro's and Con's of both then it would help them to make the correct and most cost effective decisions when it comes to maintaining their home or business' exterior. 

Here's a look at what I'm rambling on about...

Aggressive Approach Pro's

Mossgo Pro Approach Pro's

Looks Clean
Leaves live spores behind
Kills all organic growth 
 Slower Cleaning Time
Quick Results
Destroys finish and protective surface
Protective surface  finish unharmed

Shortens life span of the surface
 Life span of surface improved

Re-Growth encouraged
Re-growth inhibited
Retains dirt and grime
Less dirt and grime retained
Retains Moisture
Allows for quicker drying times
Harsh Chemicals remain present
Gentle approach
Severe Chemical Hazard
Low environmental footprint
Dangerous power washing at heights
Safer high access operating system
More Expensive- False economy
Less expensive- Improved economy

Right, I'm off again.

Thanks for taking a few moments to check out my post and thanks to Michael Conway and Francois Moal of MossgoPro for providing the info. 

Feel free to leave any comments below, good, bad or indifferent...

If no-one hears from me in the next few months then I have most likely been kidnapped by a group of hardcore pressure washers and am being tortured at around 3,000 psi but don't worry the effects won't last (",)

Good Luck... 

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Keeping a roof clean

Posted on 13 May, 2013 at 13:00 Comments comments ()
Keeping a roof clean 
By F. Moal 

When looking at an ageing building, few people cast a critical eye at the state of the roof. The windows are clean, the garden tidy and the interior spotless, but the roof is almost invariably unkempt. Black moulds hide it's colour and moss slowly mats itself in the bonds, so slowly that few take notice. 

The encroachment of grime and moss has it's effects :  Beyond the architectural downgrade the fabric of the building is at risk. Doing nothing is ultimately the expensive option. The risk varies with the nature of the roofing material : Thatch and wood shingles are at a more immediate risk of decay. 
Metals erode under the acidic releases of lichen and moss. Lead and zinc used in soakers and rainwater disposal will thin down to eventually leak. Clay tiles need to dry between rainfalls to fulfill the promise of durability - if not premature shaling or frost damage may occur. 
On all material the permanent presence of a bio film is deleterious by increasing capillary creep in laps and interstices. This in turn leads to undetectable moisture ingress. Generally materials retaining moistures are prone to contamination and combined with a shady winter exposure porous materials such as concrete tiles will become a good host for moulds such as A. Niger, then algae, followed by moss and lichen. As the bio film becomes established, the moistures are more permanent, and the cycle accelerates. 
Architects do not seem to enter this constrain in their choice of roof material : 
This was of no consequence in the days of acidic rain, but  cleaner air results in nature reclaiming it's place in unforeseen ways. There is no easy answer to the return of nature :  
Excessive moss has to be removed by hand. Mechanical means used on the ground are ill adapted to a pitch roof.  
Jetting causes irremediable erosion to the surface. As a result the un-wanted host returns with a vengeance, only to hide the uneven, permanent discolorations of the roofing tiles. After clearing the roof from the bulky growth the next and final step is to spray the area with a dedicated anti algal wash. The right product, such as Mossgo-Pro will kill the remaining biological life at the surface and, most importantly, in laps and interstices. The dead bio film will soon loosen under diurnal cycles, helped by the wind, rain, heat and frost. 
Self cleansing is a lengthy affair - months in most cases with latent effects stretching over a period of two or three years. The roof will become cleaner with the change of seasons and reveal it's original colour and texture. 
There is no known preventative measure of any durability. 
Clear hydrophobic  resins degrade under UV in a matter of months. The same causes - substrate porosity and sun exposure - will have the same effects, at the same rate. This however is slow and a roof treatment is to be regarded as decennial maintenance. 
Further maintenance will not be as heavy as the first clean, if carried out as or before the surface contamination triggers the condition for accelerated growth. 
On the continent, antiseptic roof shampoo has been standard practice for decades. Roofing firms offer it as a standard way of finishing remedial work and as preparation to fitting out solar panels. In Britain the practice is expending quickly :  The process has been adapted to the northern more demanding climate of the British Isles. 
The website hosts a wealth of information on roof maintenance treatment. 

HD Roofing Services in Ireland, are among the most experienced contractors to use the Mossgo pro roof cleaning system. For more info or advice call Andrew on 087 9323863 or mail him at [email protected]  

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Walls, rough cast render and pebble dash cleaning.

Posted on 15 April, 2013 at 13:28 Comments comments ()
Hi Folks,

Just a quick one on something that we are coming across a fair bit lately.

Wall Cleaning 

Walls, roughcast renders and pebble dash treatment. 

The extensive use of rough cast renders and pebble dash on walls has led to the development of appropriate cleaning techniques. 
Coloured renders or Monochouche as it’s also known was particularly popular during the most recent building boom here in Ireland.  
Although the new build industry has all but gone these types of plastering are appearing more and more as services such as External Insulation continue to grow. 
There’s nothing wrong with these wall coverings, done right they actually look really well and versus a traditionally plastered then painted wall I’d choose a coloured render all day long. 
Like all external surfaces though it’s only a matter of time before they become dull, discoloured and stained from growths such as red and green algae or lichen.  Trouble is, due to the granular type finish to render or the easily loosened pebbles on pebble dashing the very last thing you would want near these surfaces is PRESSURE WASHERS! 

 I recently done a roof repair for a girl whose house was finished in a bright yellow render, the place was immaculate, you could tell she spent many hours in the garden and cleaning her home. A little too much as it happened. I asked what happened to the gable wall where I noticed a section where there was streaks going in all sorts of directions. Putting her hand to her forehead she told me that after noticing a red colour appearing on the wall she decided to try and rinse it off with her little electric pressure washer, big mistake!   
Like our Roof Cleaning technique, our treatment of Moss, Algae and Lichen is soft and safe enough to use on any type of external surface without any risk of damage to the substrate, and without the use of PRESSURE WASHERS!

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Roof Coatings, the truth.

Posted on 11 March, 2013 at 7:36 Comments comments ()
Just when we thought it was time to pack away the winter woollies out pops Met Eireann with a weather warning, and not just an ordinarily weather warning either, an orange status warning! This can mean only one thing Sneachta! The country grinds to a halt, mass chaos in the aisles of Tesco... ok slight exaggeration, but it has given me a few hours to get a post done on here.
While pricing roof cleaning jobs I have been asked a fair bit about Roof Coatings or Roof Painting as it is also known. It is not something I was ever familiar with down the years or anything I'd ever taken any notice of but since starting my own business 18 months ago it is something I have been forced to look into in order to keep up with the competition or just to have an opinion for the asking customer.
We have been approached by a few companies about using their products or being involved in their roof coating franchise but although there does seem to be a market for it, I see it as being nothing more than a gimmick. 
While reading up on the subject I came across a site on here a the author of the page Richard Jones sums it up perfectly for me, here's some of what he has to say:

Roof Coating And Sealing
More and more roof coating companies seem to be popping up these days and as usual many of them make very extravagant claims. I wanted to take this opportunity to set the record straight, once and for all, written by me, a very experienced roof tiler and contractor.

"A Roof Coating Will Extend The Life Of Your Roof"
This statement should really be taken with a pinch of salt. If a new roof costs £5000 and is expected to last 75 years+ and a roof coating costs £4000 and lasts 10 years (if you are very lucky), would you feel this is value for money?

Roof Sealants Will Improve The Thermal Effiency Of The House
This is a statement I have seen several high profile roof companies make and in my opinion is ridiculous. A thin layer of paint/coating will offer as much insulation as a coat of Marmite. I feel the reason new houses are constructed with traditional insulation products is because they work much better and are much cheaper than expensive coatingsMany high pressure salesman use this claim as part of their pitch and my advice is to fix any insulation issues with the property by purchasing more insulation - not roof coatings.

Become A Show Home - Get A 10% Discount
This is one of the oldest tricks in the book, a discount is apparently offered if the house is the first in the area to have a roof coating applied. It's best to avoid such sales tactics, it is a sign of desperation from a company that cannot reach new customers by word of mouth and is designed to rush you into a purchase.

The Ten Year Guarantee
Read the small print folks, if you cannot see specific details of what is included or excluded then it's not worth the paper it's written on.Here is an example of how one company advertises it's special 10 year guarantee:
Does the guarantee cover the product if it peels/washes off the roof?
Does the guarantee cover moss re growth on the tiles?
Has the company that offers this guarantee even been in business for 10 years?
Remember: A vague guarantee without specifics is worthless.

He goes on to expose some well known companies in the UK and gives testimonials from a number of customers who unfortunately learnt the hard way.

Ads have been popping up in my local paper of late and I've also noticed a few roofs around that look to be painted, I will keep an eye on these over the coming months and watch how long the stuff actually lasts. 
For now though the snow seems to have cleared so I'm off to do a bit, Good Luck!

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Breaking the Mould

Posted on 10 January, 2013 at 5:14 Comments comments ()
Breaking the Mould   

      Mould is easier to clean than the soot of old, but with the return of clean air, nature has reclaimed ground in a way not always foreseen. Problems sometimes arise when a building does not receive its full share of sun. In other places there are not enough sunny days in a year to stop deleterious growth. The issue does not affect all materials in the same way. Most roofing materials will someday need cleaning, but not all, and not at the same intervals. Choosing a roofing material with regard to its susceptibility to mould and moss encroachment is good design practice in shady locations. Below is a brief summary of material behaviours towards biological growth and reactivity to a non-aggressive biocide treatment.
Natural slates are not porous and display a smooth surface. As a result the material dries rapidly and is not naturally prone to roof growth with the notable exception of yellow lichen in coastal environments. The material cleanses readily upon treatment. It is a product of choice for shady locations. 

Manmade slates offer some of the advantages of natural slates, but not always to the same degree.
Fired clayof good quality is not porous. The surface dries rapidly and sheds the bio film satisfactorily when treated. The roof surface is however more textured than slates offering intersects where growth can take a foothold. 
Old clay tile roofs are fragile and are best treated from the eaves.   

Concrete tilesare not indicated in the vicinity of tall trees. The high porosity combined with a rough surface provides a natural host surface. Removing mated moss from concrete tiles is labour intensive. The material cleanses well, but more slowly than other materials. The alkalinity of the surface seems to benefit black blanket moulds. In recent years smooth and less absorbent concrete tiles have arrived on the market. They are a better choice for higher humidity regions.
Zincis not a natural host to live contaminants. It is however susceptible to organic acid releases from rotting leaves, moss and lichen and should be avoided on lower draining slopes and box gutters. 

Leadis also not a natural substrate for life. It is vulnerable to mild organic acids but paradoxically resistant to harsher mineral ones. Mossy tiled roofs draining into lead gutters will eventually jeopardise its integrity. 

Copperhas biocide properties. Water running over copper will acquire some of its cathodic properties by contact and hampering further downstream growth. The protection may not be sufficient to maintain the tiles in pristine condition along the whole rafter length. On canal tiles the protection is limited to the trough, where it is still the most needed. 

Aluminiumis not particularly affected by acid releases. Water running over it will become anodic and display the reverse effect to that observed on copper. The illustration of this is seen in the splash area of TV aerials.   

Flat roof feltsof bituminous kinds are not unduly prone to moss, but ponding, cluttered designs and raised walkways will host them. PVC felts become very slippery, but as is usual with algae, the treatment is rapid.   

Organic materialsare best used in full light where they can dry rapidly. Durable presence of moulds and algae will eventually jeopardise their integrity as roof covering. As the lining of wood shingles washes away, the grey cellulose needles are exposed and offer a slightly abrasive surface hosting algae. The treatment will reinstate the silver grey appearance for some time. Thatch, if badly affected will need combing beforehand.   
 For the existing stock, periodical maintenance is the solution. The general wisdom is to opt for the milder cleaning processes before considering harsher ones. Blanket moss has to be removed by hand, bagged and disposed of in all cases. The tiles can then be treated by the appropriate biocide. After the treatment, the dead bio-film will begin to loosen under diurnal and seasonal cycles, until the roof has regained the true original colour of its material. The rate of cleansing will vary greatly with the type of material, and the exposure to wind and driving rain. Not all chemicals are appropriate, and a few only authorised by the Health and Safety Executive (HSE). All formaldehydes, caustic soda or bleach based chemical are proscribed. 
The application method and knowledge is as important as the biocide itself. Jet cleaning is seldom appropriate to roof cleaning. The pressure removes surface aggregates, creating a moisture retaining surface favourable to the return of the contaminants. Tile impregnation and coatings are ways of mitigating the damage done by jetting, but at a cost sometimes higher than simply replacing the tiles by new ones. In conclusion, the return of clean air means new parameters for the choice of roofing materials by the Architectural Technology professional, and the specification of a nonaggressive maintenance procedure for existing roofs. This is easily searched for on the Internet. A comprehensive approach to roof cleaning and the provision of specification support is a sign of an experienced specifier.   

The author is Managing Director of TVSPLtd, which specialises in a roof cleaning process known as the Mossgo Roof System, supplier to HD Roofing Services Ireland.
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Natural slate, repair and maintenance.

Posted on 9 December, 2012 at 8:18 Comments comments ()
Hi there!
Its been a while since my last post here, mainly down to the fact we have been very busy over the last few months. A complaint I hope to use more often!!
Anyway, I'd like to thanks those who have took time to read my posts over the last year, and those who have left comments, both positive and negative. Like everyone I learn from the opinions of others.

I recently came across an article written by an american guy called Jeffrey S. Levine, all about natural slate roofing and just wanted to share a short extract with you that highlights some important tips when it comes to repairing and maintaining this type of roofing. I like how he mentions the use of mastic or glues as a no, no when it comes to making repairs, something many roofers or repair men use as a quick fix or easy way of making a quick quid...

Repairing Slate Roofs:

Broken, cracked, and missing slates should be repaired promptly by an experienced slater in order to prevent water damage to interior finishes, accelerated deterioration of the roof and roof sheathing, and possible structural degradation to framing members.The damaged slate is first removed by cutting or pulling out its nails with a ripper. If steel cut nails, rather than copper nails, were used in laying the roof, adjacent slates may be inadvertently damaged or displaced in the ripping process, and these, too, will have to be repaired. If the slate does not slide out by itself, the pointed end of the ,slate hammer can be punched into the slate and the slate dragged out. A new slate, or salvaged slate, which should match the size, shape, texture, and weathered color of the old slate, is then slid into place and held in position by one nail inserted through the vertical joint between the slates in the course above and approximately one inch below the tail of the slate two courses above. 
copper bib protecting newly created nail hole 
After removing the deteriorated slate and sliding the new slate into place, it is secured with a copper nail. A copper bib (shown here) is formed to protect the newly created nail hole. Finally, a slate hammer is used to push the bib in place over the nail head. Photo: Jeffrey S. Levine.To prevent water penetration through the newly created nail hole, a piece of copper with a friction fit, measuring roughly 3" (7.5 cm) in width and 8" (20 cm) in length, is slid lengthwise under the joint between the two slates located directly above the new slate and over the nail. Alternate methods for securing the replacement slate include the use of metal hooks, clips, and straps that are bent over the tail end of the slate. The application of roofing mastic or sealants to damaged slates should not be considered a viable repair alternative because these materials, though effective at first, will eventually harden and crack, thereby allowing water to enter.
Mastic also makes future repairs more difficult to execute, is unsightly, and, when applied to metal flashings, accelerates their corrosion.When two or more broken slates lie adjacent to each other in the same course, or when replacing leaky valley flashings, it is best to form pyramids (i.e., to remove a diminishing number of slates from higher courses) to keep the number of bibs required to a minimum. When reinstalling the slates, only the top slate in each pyramid will need a bib. Slates along the sides of the pyramid will receive two nails, one above the other, along the upper part of its exposed edge.

A roof and its associated flashings, gutters, and downspouts function as a system to shed water. Material choices should be made with this in mind. For example, use a single type of metal for all flashings and the rainwater conductor system to avoid galvanic action. Choose materials with life spans comparable to that of the slate, such as nonferrous nails. Use heavier gauge flashings or sacrificial flashings in areas that are difficult to access or subject to concentrated water flows. 
Flashings are the weakest point in any roof. Given the permanence of slate, it is poor economy to use anything but the most durable of metals and the best workmanship for installing flashings. Copper is one of the best flashing materials, and along with terne, is most often associated with historic slate roofs. Copper is extremely durable, easily worked and soldered, and requires little maintenance. Sixteen ounce copper sheet is the minimum weight recommended for flashings. Lighter weights will not endure the erosive action of dust and grit carried over the roof by rain water. Heavier weight, 20 oz. (565 grams) or 24 oz. (680 grams), copper should be used in gutters, valleys, and areas with limited accessibility. Lead coated copper has properties similar to copper and is even more durable due to its additional lead coating. Lead coated copper is often used in restoration work.Terne is a less desirable flashing material since it must be painted periodically. Terne coated stainless steel (TCS) is a modernday substitute for terne. Although more difficult to work than terne, TCS will not corrode if left unpainted; a great advantage, especially in areas that are difficult to access.Once a metal is chosen, it is important to use it throughout for all flashings, gutters, downspouts, and metal roofs. Mixing of dissimilar metals can lead to rapid corrosion of the more electronegative metal by galvanic action. Where flashings turn up a vertical surface, they should be covered with a cap flashing. Slates which overlap metal flashings should be nailed in such a manner as to avoid puncturing the metal. This may be accomplished by punching a second hole about 2" (5cm) above the existing hole on the side of the slate not overlapping the metal flashing. It is important that holes be punched from the back side of the slate. In this way, a shallow countersink is created on the face of the slate in which the head of the nail may sit.The use of artificial, mineral fiber slate is not recommended for restoration work since its rigid appearance is that of a manmade material and not one of nature. Artificial slates may also have a tendency to fade over time. And, although artificial slate costs less than natural slate, the total initial cost of an artificial slate roof is only marginally less than a natural slate roof. This is because all the other costs associated with replacing a slate roof, such as the cost of labor, flashings, and tearingoff the old roof, are equal in both cases. Over the long term, natural slate tends to be a better investment because several artificial slate roofs will have to be installed during the life span of one natural slate roof. 
application of roofing felt 
Roofing felt is being installed over the decking; a rubberized membrane is used selctively at the eaves and under some flashing. Photo: NPS files.Clear roof expanses can be covered by an experienced slater and one helper at the rate of about two to three squares per day. More complex roofs and the presence of chimneys, dormers, and valleys can bring this rate down to below one square per day. One square per day is a good average rate to use in figuring how long a job will take to complete. This takes into account the installation of flashings and gutters and the setup and breakdown of scaffolding. Tear-off of the existing roof will require additional time.
Repair/Replacement Guideline

The following guideline is provided to assist in the repair/replace decision making process:
1. Consider the age and condition of the roof versus its expected serviceable life given the type of slate employed.
2. Calculate the number of damaged and missing slates. Is the number less than about 20%? Is the roof generally in good condition? If so, the roof should be evaluated for repair rather than replacement. Also, keep in mind that the older a roof becomes, the more maintenance it will likely require.
3. Determine if there are active leaks and what their source may be. Do not assume the slates are leaking. Gutters, valleys and flashings are more likely candidates. "False leaks" can be caused by moisture condensation in the attic due to improper ventilation.
4. Check the roof rafters and sheathing for moisture stains. Poke an awl into the wood to determine if it is rotted. Remember that very old, delaminating slates will hold moisture and cause adjacent wood members to deteriorate even if there are no apparent leaks.
5. Are many slates sliding out of position? If so, it may be that ferrous metal fasteners were used and that these are corroding, while the slates are still in good condition. Salvage the slates and relay them on the roof. If the slates have worn around the nails holes, it may be necessary to punch new holes before relaying them.
6. Consider the condition of the roof's flashings. Because slate is so durable, metal flashings often wear out before the slate does. Examine the flashings carefully. Even the smallest pinhole can permit large quantities of water to enter the building. Is the deterioration of the slate uniform? Often this is not the case. It may be that only one slope needs replacement and the other slopes can be repaired. In this way, the cost of replacement can be spread over many years.
7. Press down hard on the slates with your hand. Sound slates will be unaffected by the pressure. Deteriorated slates will feel brittle and will crack. Tap on slates that have fallen out or been removed. A full, deep sound indicates a slate in good condition, while a dull thud suggests a slate in poor condition.
8. Are new slates readily available? Even if replacement is determined to be necessary, the existing roof may have to be repaired to allow time for documentation and the ordering of appropriate replacement slates.


Given the relatively high initial cost of installing a new slate roof, it pays to inspect its overall condition annually and after several storms. For safety reasons, it is recommended that building owners and maintenance personnel carry out roof surveys from the ground using binoculars or from a cherry picker. Cracked, broken, misaligned, and missing slates and the degree to which delamination has occurred should be noted, along with failed flashings (pin holes, open seams, loose and misaligned elements, etc.) and broken or clogged downspouts. A roof plan or sketch and a camera can aid in recording problems and discussing them with contractors. In the attic, wood rafters and sheathing should be checked for water stains and rot. Critical areas are typically near the roof plate and at the intersection of roof planes, such as at valleys and hips. Regular maintenance should include cleaning gutters at least twice during the fall and once in early spring, and replacing damaged slates promptly. Every five to seven years inspections should be conducted by professionals experienced in working with slate and steep slopes. Good record keeping, in the form of a log book and the systematic filing of all bills and samples, can help in piecing together a roof's repair history and is an important part of maintenance.As part of regular maintenance, an attempt should be made to keep foot traffic off the roof. If maintenance personnel, chimney sweeps, painters, or others must walk on the roof, it is recommended that ladders be hooked over the ridge and that the workmen walk on the ladders to better distribute their weight. If slates are to be walked on, it is best to wear soft soled shoes and to step on the lowermiddle of the exposed portion of the slate unit.


Slate roofs are a critical design feature of many historic buildings that cannot be duplicated using substitute materials. Slate roofs can, and should be, maintained and repaired to effectively extend their serviceable lives. When replacement is necessary, details contributing to the appearance of the roof should be retained. High quality slate is still available from reputable quarries and, while a significant investment, can be a cost effective solution over the long term.
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Importance of roof maintenace

Posted on 27 August, 2012 at 9:39 Comments comments ()
Roof maintenance is very important to promote a long lasting roof. An effective roof is critical to the overall protection, insulation, security, and fiscal investment of a home. Neglect to this vital part of a property can result in significant damage and costly repairs or needed replacement. The type of roofing material utilized has influence over the best maintenance strategies to promote optimum roof condition. Regular inspection, cleaning, and other tactics will help keep the roof operational as long as possible. 
Inspecting the roof periodically is one of the first steps for proper roof maintenance. Inspections are particularly important in late autumn and early spring. Visual inspections should analyse for loose, missing, or broken slates, cracked tiles, and frayed edges. If applicable, flashings around roof openings such as skylights, chimneys, and vents should be given special attention. 
Proper cleaning of the roof is some of the most regular preventive care activities that should take place. The accumulation of dirt, leaves, and debris should be periodically removed to minimise deterioration of the roof. The accumulation of snow is especially problematic for certain types of roofs in the winter and this should be attended too before it overburdens the structural integrity of the roof. 
Gutters should be regularly cleaned and have debris removed from them, this can help prevent water build up and blockages that can lead to bursting gutters and possible flooding. Trees that are in close proximity to the house should have branches trimmed that may pose a threat to the roof in high winds, this tactic will also help prevent leaves, dirt and tree sap from further clogging up the roof. The actual branches can damage the roof if allowed to.  
Moss, lichen and algae on a roof disturbs the flow of rainwater across the roof surface. Growth thrives where the supply of moisture is best and establishes itself where the slates overlap especially along the lower edge, the tail end, of the slate.During heavy rain, the lap cavities will overflow inside the building. Most roofs have a notional second line of defence in the form of a bituminous felt, but it does not always perform perfectly and is not designed for long term protection.The battens and fixings, situated above the felt undergo accelerated decay. Moss release small amounts of organic acids that are corrosive to metal, particularly the lead and zinc used in soakers and flashings.
roof-tiles-diagram. Diagram showing effect of dirty slate when wet.

As I've touched on before in earlier posts, roof cleaning should be done using specially developed soft washing techniques and without the use of any type of pressure washer. Using insured and experienced roofing contractors who know what they are doing is strongly advised.
Proper maintenance of your roof can save you thousands in the long run, all materials have an expected lifespan but this lifespan is greatly reduced due to a lack of maintenance.

We offer services that help cover all areas of roof maintenance from snow guards to low pressure roof cleaning. We also provide inspections to identify any weaknesses and these are given in detailed reports with pictures and are completely free to most homeowners!
Give us a call for more info or advice. 

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Reasons why you should not pressure wash a roof

Posted on 21 June, 2012 at 9:02 Comments comments ()
I have been asked recently about some of the posts and comments I have been making on things like Facebook and Twitter regarding why you should never pressure wash your roof. 
A power washing company recently sent me an e-mail asking for reasons why I think this. So here you go...
The three most commonly used roofing materials in Ireland are probably concrete tiles, fibre cement (man-made) slates and natural slates. I can give you a few examples for each as to why they shouldn't be pressure washed, and anyone experienced in fitting these products will tell you the same.

Concrete Tiles
I feel like I've beaten this one to death over the last few months but it is the most common cause of leaks that we come across. On a concrete tile you have a lip either side, one high one low, so side by side they interlock. If the lower lip of the tile breaks, and the break is higher than the headlap (the coverage you have with one tile over another) then you have hole in your roof. This is a weak point on most tiles, and some so much so that a tap of a knuckle will break it easily not to mention a pressure washer. 
Leak sourcing and repair.These holes may be already present on the roof before a pressure washer gets there and becuase they are covered by the higer lip, would not be seen without inspection of every individual tile. Then follows the increased flow of water into the hole, with only in some cases an underlay to keep it from some very expensive damage. 

Fibre Cement Slates
These man-made slates were definitely the favoured choice of most  building contactors during the now distant construction boom in Ireland. They offered a cheaper alternative with the same sleek finish as the more expensive natural slate, but unfortunately have no where near the life expectancy or colour durability of the natural stone alternative. 
Over a short period of time weathering takes its tole on this type of material, on installation these slates can withstand a certain amount of bending before they break, after a couple of years on the roof they become almost as brittle as a thin sheet of glass and again a tap of a knuckle is enough to break them.
Effects of moss growth. Damaging moss growth. With only a thin protective layer on these slates, moss and lichen can eat through them very easily and expose the the inner layers rendering the slate next to useless. Also a with moss's ability to hold water like a sponge, expansion between the joints and ends of the slates can cause the now brittle slate to snap. The slates are fixed at three points, two nails either side and a copper crampon at the bottom, because of this even broken slates often stay in place and to the eye all looks as it should do without close inspection.
Add a couple of thousand p.s.i. to these weaknesses and you will only shave years of the already short lifespan of fibre cement slates.

Natural Slate
If well maintained and cared for correctly, natural slates will last a number of lifetimes and in most cases will only give problems when they've outlived the man made fixing they were fitted with.
Like all natural products no two are the same, gradient, texture and shape differ with every slate. Because of this each slate has its own level of durability. When laid out on a roof it is next to impossible to tell which slates are strong, which are weak, or if they may be cupped slightly. For this reason, not matter how careful, foot traffic should be kept off natural slates completely so not to run the risk of any damage. 
The very same has to be said for pressure washers. 
Before pic natural slate roof kildare village. Dark algae and lichen.after image of natural slate roof cleaned by HD Roofing Services Ireland 
With each of these materials, moss and algae can grow in and under joints and completely out of reach of the spray of any pressure washer.
The reason the person is having the roof cleaned in the first place is so that these growths are removed. Leaving bits behind to continue the organisms reproductive cycle is pointless and at best will only keep the roof looking clean for a few months, before things start heading back to square one.

These are only an example of reasons not pressure wash a roof, and i'd be here all day if I was to go on.
We, at the same time, do highly recommend keeping a roof cleaned and well maintained for reasons I will touch on more next time. Just know your options, you really do get what you pay for.

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Behaviour of Algae, Lichen and mosses

Posted on 6 June, 2012 at 9:34 Comments comments ()
Algae are a diverse group of simple, plant like organisms. Like plants, most algae use the energy of sunlight to make their own food, a process called photosynthesis. However, algae lack the roots, leaves, and other structures typical of true plants. Algae are the most important photosynthesising organisms on Earth. They capture more of the sun’s energy and produce more oxygen (a by-product of photosynthesis) than all plants combined. Algae vary greatly in size and grow in many diverse habitats. Microscopic algae, called phytoplankton, float or swim in lakes and oceans. Although most algae grow in fresh water or seawater, they also grow on soil, trees, and animals, and even under or inside porous rocks, such as sandstone and limestone. 

Algae also form mutually beneficial partnerships with other organisms notably with fungi to form lichens-plant-like or branching growths that form on boulders, cliffs, and tree trunks.The algae provide oxygen and complex nutrients to their partner, and in return they receive protection and simple nutrients. This arrangement enables both partners to survive in conditions that they could not endure alone.There are more than 15,000 kinds of lichen in the world. They can grow on any surfaces and anywhere in the world. The lichen is a symbiotic association between a fungus (mycobiont) and an alga (photobiont). The filaments of the fungus support cells of the algae.The fungus needs carbon and energy. Generally it finds it on dead organic material or on living organisms (parasitism) which cause disease to plants. The algae, capable of photosynthesis, provide the carbohydrates it needs. It also provides some vitamins (biotin, thiamine). The algae changes the structure of the fungus which can absorb a lot of water and a part of sunlight to protect the algae from certain strong wavelengths.The fungal component of lichens produces organic acids that disintegrate rock, giving the lichen a better hold and contributing to the weathering process, which eventually turns a rock into soil. Lichens can withstand great extremes of temperature and are found in all parts of the world. In the built environment, the organic acids are notoriously deleterious to zinc and lead used for flashing or gutter lining. 

Many small plants bearing the name moss are not mosses in that they do not belong to the Bryophyta family. The “moss” found on the north side of trees is the green alga Pleurococcus;Irish moss is a red alga. Beard lichen (beard moss), Iceland moss, oak moss, and reindeer moss are lichens. Spanish moss is also a term used for a lichen. The term moss used in connection with MossGo does not refer to Bryophytas, but to the vernacular use of the word.   
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