Outdoor Roofing

Flat Roofing Materials

Roofing Felt

Commonly glass-fibre or polyester fleece, impregnated with a bituminous material such as tar or asphaltic bitumen. Usually coated on one side with a mineral to help protect the felt from sunlight and weather damage. Available in a range of sizes, but commonly sold in 1m x 10m rolls.

Fibre-Based Felt
Generally used for garden sheds and wooden outbuildings. Fibre-based felt can be used alone or combined with a sheet underlay. Fibre-based felt is attached using roofing nails and/or roofing felt adhesive. It is relatively cheap and easy to work with and fit.

Glass Fibre Felt
Often used on garages and extensions, but can also be used on garden sheds for a longer lasting roof. Glass fibre felt is more expensive than traditional fibre-based felt, but it will last longer and provide better protection than the cheaper option. Glass fibre felt should always be combined with either one or two layers of underlay, depending on the situation. When used to roof an extension to your home, a three layer system should always be used. It is applied using either cold felt adhesive or hot bitumen.

Polyester Felt
Also used more for garages and extensions than sheds. Polyester felt should be handled and fixed in the same way as glass fibre roofing felt, with at least one layer of underlay and using cold adhesive or hot bitumen.

Torch-on Felt
Generally only used on garage and extension roofs, Torch-on felt is a very hard-wearing alternative to the other types of felt, but is best applied by professionals. As the name suggests, torch-on felt is applied using a gas torch, and can be combined with an underlay or laid in a single layer. As you would expect, this is a more expensive option that the previous two, but also provides a longer lasting finish.

Flat Roofing Treatments

There are several ways to protect your flat roof, and therefore prolong its life. All of these treatments are best applied as soon as the roof is completed, rather than using them to try to salvage an already problematic roof.

Elastomeric (liquid Rubber) Emulsion
This thick waterproofing emulsion can be used to add an additional layer of protection to flat roofs covered in asphalt, asbestos or even corrugated iron. It is simply brushed on, either in combination with a primer or on its own, and left to harden. Be careful to follow the manufacturers instructions for the best results.

Aluminium Paint
Aluminium paint helps to reduce the damage that sunlight will do to a felted roof by reflecting some of the heat and light. Can be applied to most types of felted roof, as well as corrugated iron sheets. Aluminium paint should be brushed on fairly thickly for the best results and works best for dark coloured roofs (which, to be honest, is most flat roofs…)

A thin layer of limestone, granite or flint chippings spread over the felt of a flat roof will help to reduce damage by sunlight and rain. Perfect for flat roofs in very sunny positions.

Flat Roof Repair Materials

There are several options when it comes to repairing holed, ripped and worn flat roofing materials. Not all are suitable for all situations, so be careful to choose the one best suited for the repair you are undertaking.

Acrylic Coating
Suitable for small areas and complete roofs. Acrylic coating can be brushed or rolled on, and should be applied fairly thickly and in an even coat.

Bitumen Waterproofing Solution
Great for sealing small holes in felted roofs, bitumen solution is like thick, sticky paint. For increased strength, reinforcing mesh can be embedded in the solution and then brushed over.

Bitumen Mastic
Used for small repairs on felted and flat roofs. Applied with a trowel and can be used to fill cracks and holes as well as covering worn areas.

Roof and Gutter Sealant
For sealing cracks in flashing and roof felt. Usually applied with a cartridge gun and then worked with a filling knife.

Roof and Gutter Repair Tape
A cleaner option for sealing cracks and splits in flashing and felt. Has a self-adhesive backing and is simply pressed on and rolled (with a seam roller) to seal the edges.

Flashing Strip
For repairing or replacing flashing, but can also be used to patch felt or asphalt roofs. The area should be cleaned and primed before use. Self-adhesive backing makes this a clean and easy option.

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