Frequently Asked Questions
What is a cold roof?
Many residential flat roofs have the waterproofing laid directly onto the deck, and any insulation placed above the ceiling. This arrangement allows the deck to become ‘Cold’.
In cold weather, such roofs are inherently prone to condensation, which can cause materials to decay and distort. To reduce this risk, through-ventilation has to be provided to each and every space above the insulation but this is often difficult to achieve, for example if the roof abuts the wall of a house.
Cold roofs should not be endorsed for the climatic conditions in Scotland, according to the Building Standards (Scotland) Regulations. Although the Regulations do not prevent the use of cold roof constructions, warm roof constructions are recommended.
If you have an existing cold roof in need of refurbishment, it should be converted to a warm roof.
What is a Warm Roof?
The construction of the roof deck and ceiling has an important effect on the behaviour of the waterproofing material on top. The building industry uses the terms WARM ROOF and COLD ROOF to describe the two different types.
In Britain as a whole, the Warm Roof is strongly recommended.
This type of construction has the insulation above the roof deck, thus keeping the deck ‘Warm’. This is usually the most satisfactory construction for domestic properties as it avoids the need for ventilation of the roof structure.
What is the basic design of a flat roof?
In a flat roof, the waterproofing is always supported by a structural roof deck. This is usually a timber boarding of some type, which in turn is supported on joists. The ceiling, if any, is usually fixed directly to the underside of the joists.
Garages may be un-insulated, but most roofs above the habitable part of the house will be insulated to comply with Building Regulations. In houses the insulation is sometimes placed immediately above the ceiling. Preferably, it may be placed above the deck before the application of the waterproofing.
Some specialised insulations can also be placed above the waterproofing, but this sort of construction is normally confined to commercial and industrial buildings and has very seldom been used on domestic buildings.
In almost all cases where RBM has been installed, the surface of the waterproofing will need protection, both from ultraviolet light and from fire from external sources. The Building Regulations lay down the degree of protection required in the case of fire. This can be achieved by adding a layer of mineral chippings bedded in compound to the surface of the roof, or alternatively by using a mineral surfaced layer of RBM as the top layer, or ‘Capsheet’. Liquid applied and Single layer systems have this protection built in and do not require additional protection.
Don’t flat roofs pool water?
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Will my roof be guaranteed?
Most roofing contractors will offer a guarantee on their flat roof installations, but the length of time the roof will last for will vary between independent contractors.
Here at Abbey Roofing, our flat rubber roofs come with a 50 year guarantee, and our felt roofs come with a 20 year guarantee.
Why choose a flat roof?
A flat roof can be beneficial for homeowners who are wanting to make the most of their space – unlike a sloping roof, a flat roof allows all of the height in the rooms below to be used, keeping the home interior light and airy. A flat roof is also a good option for those who are considering adding a roof terrace or garden to their property, with the level ground making access easy.
As flat roofing requires less materials and labour than a pitched roof, flat roofing is often more affordable, so is a perfect choice for those on a tight budget.
How often should I have my roof inspected?
Inspection twice a year, in March and November. Try to do one inspection soon after rain, to see how well the water is draining away.
Abbey Roofing Checklist
Will a roof repair be sufficient?
If the roof is out of guarantee then patch repair compounds are useful because they give the householder time to organise re-roofing for a competitive price at the right time of year, however, always ensure that the compound is compatible with the membrane. But in general, such repairs are only short term and worthwhile if they are cheaper than the effective cost per year of a new roof covering. If it is still covered by a guarantee, contact your roofing contractor or you may invalidate the guarantee.
What is Reinforced Bitumen Membrane?
Built-up Reinforced Bitumen Membrane (RBM) are the most common material for residential flat roofs, as well as for major roofing contracts and there has been a lot of product development in recent years.
Two or three layers of sheet materials are rolled out over the roof and bonded together with hot bitumen. These sheet materials are based on a carrier normally polyester of varying strengths and coated in bitumen so that they fuse together to form a single waterproof layer.
The membrane is laid onto insulation when applied over a heated building or part of a building with the insulation bonded to a vapour control layer which in turn is attached to the roof deck. This build up is known as the warm roof and is very successful.
What is Single Ply?
Single ply membranes have been in use in the UK roofing for over forty years and provide waterproof protection not only to very large buildings such as airports and supermarkets but also to private houses. They are based on polymers derived from oil that have been formulated for very long term flexibility and resistance to solar radiation. These are formed into large sheets ranging in thickness from 1.2-2.0mm and usually supplied in rolls 1-2m wide and up to 20m long. Some products are supplied in large sheets to fit the roof and delivered folded up.
Single ply works best in a ‘warm roof’ system (see Sketch 1), where it is laid over insulation which is then supported by the structural deck. A ‘vapour control layer’, laid over the deck and under the insulation is always required, to stop harmful condensation building up in the insulation. Warm roofs do not require ventilation and are very reliable.
How long does a rubber roof last?
With the correct materials manufacturer such as RubberCover by Firestone, along with an independently certified, experienced, flat roof specialist contractor such as Abbey Roofing, we give guarantees on our flat roofs that range from 20 years for our felt roofs and 50 years for our rubber roofs.
These are achievable with good products, correct attachments, installation and maintenance.
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