25 Most Frequently Asked Questions

1) What are the different layers within a roof?

Within a pitched slate or tiled roof there are usually one or two layers.

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Roofs constructed pre- were usually laid without any felt or insulation underneath the rafters, meaning that the only layer protecting the loft space, loft contents, and the inside of the property was the roof tiles or roof slates themselves. This often lead to the loft space being unusable as dirt, dust and damp got underneath the roof tiles or roof slates into the roof space ruining anything stored there.

Roofs constructed between the s and s were usually constructed with a non breathable membrane underneath the roof tiles or roof slates, forming two layers. This formed an effective barrier to seal the roof from dust and dirt, but often lead to condensation being trapped, leading to moisture and damp issues.

It was rare for roofs of this age to be constructed with any insulation, although many will have had insulation added since.

Roofs constructed after the s will usually have been constructed using a breathable felt underneath the roof tiles or roof slates, sealing the roof against dust and dirt whilst still allowing it to breathe, thus preventing most condensation issues.

Insulation will often have been added as well - although this will often have been laid on top of the celiling of the rooms below the roof, meaning that the roof will still have two layers.

2) Common causes of a leaking roof

Leaks in roof are usually caused by one of three reasons:

Cracked tiles or slates

Roof tiles / slates are often cracked by contractors when work is carried out on the roof such as the installation of solar panels or cleaning windows.

Roof tiles / slates should not be walked on, and rarely survive this happening - if left,even a hairline crack will permit the ingress of water.

Cracked pointing at verges

Many roofs have cement verges. These will eventually crack allowing water into the property.

All new build properties, and many refurbishment projects, use upvc dry verges which are a 'fit and forget' product that seals verges permanently against the effects on water ingress.

Lead flashings:

Lead flashings, particuarly on older properties, are chased into the wall, with the gap, or 'chase', then filled with mortar. The expansion and contraction of the lead as it warms up in the sun and then cools at night, leads to mortar failure which in turn leads to water entering the property.

The use of silicone sealants is little better than cement, as these products will rarely last for more than a year or two in external conditions.

The solution is the use of a proper Lead Sealant which is specifically designed for this purpose and will provide many years of leak free service.

3) What is the best roofing membrane?

Many people consider premium roofing membranes by manufacturers such as Tyvek Supro and Cromar Vent 3 Pro as the best, high performance breathable membranes.

Roofing membranes can be thought of in similar terms to waterproof clothing: you would not expect a cheap 'own brand' waterproof jacket to perform as well as a branded, professional quality jacket from a leading outdoor brand at two or three times the price.

Breathable membranes for walls and roofs can be thought of in the same way: The more expensive they are, the thicker they are which means that they perform better.

Interestingly, many of our customers are aware of this - and the potential issues that can occur when the breathable membrane used is not up to the job - and our best selling roofing membranes are our premium membranes such as Tyvek Supro and Cromar Vent 3 Pro: As in many situations in life - you get what you pay for!

4) What roofing material is the best?

The answer to this is simple: No roofing material is the 'best'!

They will all 'do the job' well!

Broadly all roofing materials - whether you are looking at concrete roof tiles, clay roof tiles, man made roofing slates and natural slates for a pitched roof, or felt or GRP fibreglass products for a flat roof, have all been tested to a number of British, EU and often International standards and will have all met and exceeded them - otherwise the manufacturers would not market them, and specialist roofing materials suppliers such as About Roofing Supplies, would not risk our reputations by selling them.

Most products have lengthy warranties, with service lives that usually exceed the warrantied life.

So, if 'best' means 'which one is the most waterproof' or 'which one will last the longest?' the answer is broadly that they are all similar.

However if you are looking for 'which roofing material looks the best?' then only you can decide that as beauty is in the eye of the beholder!

5) What are roof shingles made of?

Roof shingles are made of one of two materials: Western Red Cedar wood or bituminous felt.

Wood shingles - or more accurately Cedar Shingles - are made of thin strips of Cedar. These are a very popular roof covering in North America where their light weight is emininently suited to their practice of timber frame construction for houses which are unable to bear the weight of concrete or clay roof tiles as commonly used in the UK and Europe.

Felt Shingles are made from premium quality bituminous roofing felt, cut to shape, and, like Cedar Shingles, are also extremely popular in the United States due to their light weight, long life, and ease of laying.

Our own brand felt shingles are manufactured in Russia. These felt shingles are more than capable of withstanding anything that the British weather can throw at them, and have long service lives.

Beware of cheap felt shingles - usually manufactured in China, Italy or Spain: these have a reputation of being made with poor quality bitumen and rarely last more than a handful of years.

6) Are roof shingles waterproof?

Both Cedar shingles and Felt roof shingles are eminently waterproof!

In fact, because of their light weight they are the most popular roof covering in North America, where they are used in preference to concrete roof tiles, clay roof tiles or roof slates.

American property owners put their confidence in shingles to keep their houses and belongings safe and dry - and so can you!

7) Can salt damage roof shingles?

Both cedar wood shingles and felt roof shingles are resistant to salt damage, as well as rain, ice, snow and sun.

You can fit these products with complete confidence in their ability to keep your property and belongings safe and dry!

8) Can roof shingles be installed in cold weather?

Roof shingles can be installed in virtually any weather.

Broadly they are easier to lay in temperatures over 5 degrees c as they are less brittle, however there is nothing to stop you laying them at sub zero temperatures!

9) What causes shingles to curl on a roof?

Felt roof shingles can curl on a roof when the trailing, or bottom edge, has not been fixed.

The effects of the sun can cause the bottom edge of felt shingles to lift if they are not secured, and once they start to lift the wind can often make the issue worse - in extreme conditions the shingles can be damaged or even ripped off the roof.

Premium quality felt shingles, such as our own brand shingles, have an adhesive bituminous strip on each shingle, that adheres the bottom edge of each course of shingles to the course below, thus preventing wind uplift.

10) Which roof shingles are the best?

Our own brand felt shingles are manufactured in Russia. Many people consider these felt shingles as the best available in the UK - which is why we supply them!

These felt roofing shingles are more than capable of withstanding anything that the British weather can throw at them, and have long service lives.

We strongly advise our customers to beware of cheap felt shingles, usually manufactured in China, Italy or Spain, which have a reputation of being made with poor quality bitumen and rarely last more than a handful of years.

11) What goes under roof shingles?

In the UK felt shingles are normally used on shed and garden buildings, so for these applications a 3B bituminous felt is used as an underlay as the buildings below, not being subject to habitation, do not require the installation of a breathable membrane under the shingles.

In North America, as felt shingles are the most popular roof covering on houses, a breathable membrane is used under the shingles.

12) What is the lifetime of roof shingles?

Our own brand range of felt roof shingles have a 15 year manufacturer's warranty, with an anticipated lifespan of 35+ years.

13) How to install roof shingles

Our felt and cedar shingles are quick and easy to install, and both require a minimum of skill and effort.

Installation details for felt shingles can be found here.

Installation details for cedar shingles can be found here.

14) How many squares of felt roof shingles do I need?

Calculating the quantities of felt shingles required is relatively simple:

Each pack of felt shingles covers 3 square metres.

So,the first step is to calculate the area that you need to cover:

Lets assume that you have a conventional shed with a duo pitched roof (an inverted 'v' shape) that measures 2.42m x 1.21m on each of the two sides.

2.42m x 1.21m = 2.93m2 x 2 = 5.86m2 total roof area.

5.86m2 / 3m2 packs of felt shingles = 1.95 packs of shingles required.

Always round up your requirements to allow for cuts and wastage, so we will say that you need at least 2 packs.

You also need to allow for the felt shingle ridges as well: We know that the ridge is 2.42m long.

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To cover the ridges you cut the shingle strips into the individual tile pieces, giving a coverage of 2.4 strips required per linear metre of ridge.

Therefore 2.42 l/m of ridge x 2.4 strips/lm = 5.8 strips needed = 6 strips required. There are 21 strips to a pack of shingles, so you will need to buy one pack to cover the ridge leaving 15 strips spare.

You may, in fact end up using most, if not all, of the spare shingles when laying the two sides of the roof as there was very little allowance for cuts and wastage (for which 5% is usually allowed).

15) Roof shingles vs roof tiles?

Roof shingles or roof tiles: which is the best roof covering for your property?

The answer to this varies according to where you live: In North America, over 70% of domestic dwellings have felt roof shingles as their primary roof covering, yet we have not heard of a single instance in the UK!

To comply with UK Building Regulations, you could, in theory, use felt shingles, however it is unlikely that a Local Planning Officer would accept these as being 'in keeping' with the local area.

Traditionally in the UK we have used clay roof tiles or concrete roof tiles, as well as natural roof slates or man made roof slates to cover our houses. To preserve the perceived value of your house in the eyes of potential buyers it would be unwise to use anything else - not to mention the implications for obtaining insurance cover and a mortgage.

16) How long will roof tiles last?

This is in fact two questions: Firstly, 'How long are roof tiles & slates guaranteed for?', and secondly, 'What is the life expectancy of roof tiles & slates'?

Clay roof tiles are, for example, manufactured to BRE standards with a minimum life expectancy of 60 years in normal conditions.

It should be noted however that 'life expectancy' should not be taken as a guarantee or warranty.

Broadly, roof tiles and slates will remain serviceable for many decades - we can supply natural slates with a manufacturer's guarantee of 100 years.

There are a number of factors that affect the length of each manufacturer's guarantee for each roof and the tiles or slates installed: To obtain a full manufacturer's warranty - which varies by manufacturer and product used - the roof will need to be designed by the manufacturer, installed to all the current standards using a complete suite of products and fixings from the manufacturer's own range.

In practical terms, the life expectancy of clay roof tiles will be 60+ years - on occasion customers bring in clay roof tiles or slates to be matched that are much older. We have seen clay roof tiles that are estimated to be at least 250 years old that still had plenty of life left in them.

Concrete tiles degrade over time in both appearance and integrity, and they will certainly be approaching their 'twilight years' after 60 years - having said that we are regularly asked to match concrete roof tiles laid just after the end of WW2 - over 70 years ago - that are still in fair condition.

The life expectancy of natural roofing slates varies according to the type of slate used and the quality, which will, as you would expect, be reflected in the price, with life expectancies between 30 and 100 years, whilst man made roof slates have a life expectancy of up to 60 years.

Enviromental factors such as pollution or severe weather (such as in coastal locations) can have a marked effect on roof tiles: when we see old roof tiles from within the M25 boundary surrounding London, it is readily apparent how much worse their condition is than those that we see of a similar age from the Home Counties.

Roof tiles and slates are not designed to be walked on - doing so, when installing solar panels for example, leads to many breakages and leaks.

Pressure washing of roof tiles and slates is arguably the worst thing that can be done to a roof, and it is strongly advised against. If moss is a problem or unsightly, then we recommend the application of a proper Moss & Mould Remover (such as the Alphacem Moss & Mould Remover that we supply), and that the instructions are dilligently followed.

17) Are roof tiles porous?

Yes roof tiles are porous - they absorb small amounts of water, which then evaporates harmlessly.

Does that mean that roof tiles leak? No. As long as they are not broken and are laid correctly, at the correct roof pitch, they will not leak.

18) Are roof tiles waterproof?

Yes roof tiles are waterproof.

Being porous they absorb small quantities of water, however the actual tiles will not let water through, and if laid correctly and not broken, no water will get past them into the property below.

The breathable or non breathable membrane laid underneath the tiles also acts as a secondary barrier, albeit only a temporary one.

19) Can you paint roof tiles?

We supply specially formulated paint for application to fibre cement 'man made' slates and concrete roof tiles only.

Painting natural slates or clay tiles is not recommended using any products.

The use of non specialist roof tile paints is strongly advised against.

20) Which roof tiles last the longest?

In practical terms, clay roof tiles and natural roofing slates last the longest, with usable examples over 100+ years being relatively common - on occasion customers bring in clay roof tiles or natural slates to be matched that are much older.

We have seen clay roof tiles that are estimated to be at least 250 years old that still had plenty of life left in them.

Concrete tiles degrade over time in both appearance and integrity, and they will certainly be approaching their 'twilight years' after 60 years - having said that we are regularly asked to match concrete roof tiles laid just after the end of WW2 - over 70 years ago - that are still in fair condition.

Enviromental factors such as pollution or severe weather (such as in coastal locations) can have a marked effect on roof tiles: when we see old roof tiles from within the M25 boundary surrounding London, it is readily apparent how much worse their condition is than those that we see of a similar age from the Home Counties.

Roof tiles and slates are not designed to be walked on - doing so, when installing solar panels for example, leads to many breakages and leaks.

Pressure washing of roof tiles and slates is arguably the worst thing that can be done to a roof, and it is strongly advised against. If moss is a problem or unsightly then we recommend the application of a proper Moss & Mould Remover (such as the Cromar Moss & Mould Remover that we supply), and that the instructions are dilligently followed.

21) What roof tiles are suitable for low pitch roofs?

Low pitch roofs are generally considered to be those below 22.5 degrees, and above 10 degrees.

There are a number of roof tiles available that are suitable for installation on low pitch roofs.

Concrete interlocking roof tiles such as Sandtoft Double Romans and Sandtoft Calderdales are the most popular concrete options, with the Sandtoft 20/20s being the most popular clay option.

Alternatively, another solution to the challenge of which roof tiles to use at low pitches is to use Klober Permo Extreme breathable membrane instead of standard breathable membrane.

Klober Permo Extreme breathable membrane enables the use of roof tiles down to pitches as low as 12.5 degrees (depending on the roof tiles being laid). This is a very popular option, indeed the only viable solution, where an exact match to the existing roof tiles on the main roof is essential, such as clay handmade roof tiles where the minimum roof pitch that the tiles can be installed at, being 35 degrees typically, precludes their use normally at such low pitches.

It is worth noting that the rafter length of a low pitch roof can have a bearing on whether particular tiles, even if they are suitable for that particular pitch, can be used.

22) What roof tiles for a high pitch?

Broadly you can use any roof tile up to a pitch of 75 degrees, with concrete and clay plain tiles able to be used for vertical applications at 90 degrees.

23) How to remove moss from a roof

We stock & supply Cromar Fungcidal Wash which kills lichen, moss and similar vegetation resulting in growth free roof tiles and slates.

Products such as this can also be used to remove growth on roofs, walls and other external surfaces prior to treatment with surface finishes.

Application is easy: Simply apply by brush or low pressure spray at a rate of 4m2 - 6m2 per litre per coat, and leave for approximately one hour.

The surface is then cleaned using a stiff bristled brush to remove any loose debris and a second coat can be applied if any growth remains.

The cleaned surfaces should then be left for at least 24 hours to cure, before cleaning again and washing down again, taking care to remove any white deposits which may have formed.

The use of a high pressure jet wash at any stage in this process is strongly discouraged as this has a very high liklihood of permanent damage and degradation of the roof tiles or slates.

It is strongly recommended that a trial area should be coated initially to assess the correct dosage, and that products such as these should not be applied in wet weather to prevent run off and local contamination.

24) Are roof tiles covered by building insurance?

Usually roof tiles and slates are covered by Buildings Insurance, although this may vary between providers and should be checked with your insurer.

25) What is a low pitch roof?

Low pitch roofs are generally considered to be those with a roof pitch less than 22.5 degrees, and greater than 10 degrees.

A roof pitch is the steepness / angle of the roof bearers from top to bottom.

The roof pitch will determine the amount of head room there will be in the room under the roof, though this is more of an important factor when planning a loft conversion or single story extension. 

There is a wide range of specialist products available for low pitch roofs which are available on our website in the Low pitch roofing materials section.

Where can I find roof slates, roof tiles and roofing materials near me?

You can contact us to discuss and order our wide range of roofing materials in any of our branches listed below or we can deliver nationwide:

Dorking, Surrey branch

Redhill, Surrey branch

Esher, Surrey branch

East Grinstead, West Sussex branch

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