Hampshire & Berkshire Roofing – Flat Roofs are extremely common as they are much cheaper to construct than the pitched variety. Built up felt has been by far the most used method of flat roof construction, however with advances in technology there are now alternate ‘single ply’ systems that are guaranteed for 20 years some even longer.
Hampshire & Berkshire Roofing can install or repair any type of flat roofing system, and will be delighted to provide a free no obligation survey and quotation.
Please call Andrew or Graham in our office on 01189 701539 to find out more.
Common Types of Flat Roof
Built Up Felt Flat Roofs – Flat roof is the common name, however the reality should be that no roof should be completely flat with our temperate climate. To avoid pooling and potential leaking even flat roofs should have a small incline or pitch, to allow water to run away into guttering or off the side of the roof, as is common for sheds.
There are two types of flat roof; cold roofs and warm roofs. Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof, just above the ceiling. In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. Warm roofs are recommended for homes; the insulation is applied above the roof deck with waterproofing on top which eliminates the need for ventilation and keeps the roof warm.
Typical Flat Roof Construction
Roof deck – this can be made of metal, timber, concrete, composite or plywood.
Vapour control Layer (VCL) – all warm roofs need this layer inserted between the deck and the insulation; it can be made of polyethylene membrane, bitumen sheet, polymeric foil or a self adhesive sheet.
Thermal layer – this layer can be made of a cellular material such as polystyrene which traps gases in its cell structure or fibrous material like mineral wool which traps air between the fibres to insulate.
Waterproofing layer – single ply membranes made of materials like thermoplastic or elastomeric are common. Rubber lasts longer for flat roofing because it expands and contracts with the weather. PVC or a resin type surface is also used.
Surface layer – a surface layer of something like stone chippings, mineral finish or a hard resin finish is often applied to protect the waterproofing layer.
Two basic types of roofing felt material are required:
- Underlay – this is usually supplied sand coated (to prevent the layers bonding together within the roll during storage), this should be used for all layers except the top layer.
- Top Sheet – the finish, one side is plain for bonding to the underlayer, the other side normally has some form of protection finish, mineral chippings or some form of grit.
Although these are the two basic types of felt, there are numerous different specifications available for each type – these provide different types of material/finish/ thickness – normally quoted as weight per square metre.
Light weight shed roofing felt is not suitable for flat roof construction.
Hampshire & Berkshire Selected Partners
Below is a graphic showing the logo’s of roofing products and systems we use daily. Clicking on the image will take you to the suppliers website.