Picking a flat roof covering is about the roof, not a league table. Here is how rubber, fibreglass and felt compare on the extensions and garages common around Brentry.
Many Brentry semis have a garage, porch or rear addition under a flat roof, so the same question comes up often: which covering should go on? There is no single winner. The right one depends on the shape of the roof, how it drains, the deck beneath it and how much the roof is used.
Single-ply rubber (EPDM)
A single sheet of rubber, laid with few joins, suits large plain roofs such as a rear extension or a wide garage. Fewer seams mean fewer places for water to find. It handles slight movement well. The detail at corners, pipes and upstands is where its quality shows, so that work needs a careful hand.
Where the roof sits close to a house wall, any of these materials relies on a well-formed upstand and flashing at the junction. We plan that detail first, because a handsome covering with a weak edge will still let water in.
Fibreglass (GRP)
Fibreglass is laid in liquid form over a firm deck and sets hard. Its seamless finish works well on small, awkward or cut-up roofs, such as porches and bay tops. It needs a dry, stable deck and tidy edge trims. If a roof moves a lot, this material may not be the best fit, and we will say so.
- Seamless surface with few weak points
- Moulds neatly around corners and edges
- Needs a dry, firm deck to bond to
- Edge trims and upstands formed as part of it
Felt systems
Modern felt is built up in layers, and is a familiar covering for garages, sheds and small roofs. It can be a sensible choice where the roof is simple and the aim is a sound, practical finish. The laps and joins are the vulnerable points, so the standard of workmanship matters a great deal here.
We lay felt with proper overlaps and edge detail, and we tell you honestly when another material would suit your roof better. On a simple garage roof, felt can be a perfectly good and sensible answer without needing anything more elaborate.
Deck, falls and insulation matter too
The covering is only as good as what it sits on. We check the deck for rot, set the falls so water runs to an outlet and think about insulation, especially if the extension is a lived-in room. Changing the covering without sorting a poor deck or flat falls simply moves the problem to the next layer.
Choosing sensibly
Ask the installer to name the material, explain how edges and upstands are finished, and say what will happen to the old covering. Flat roof work may need planning or Building Regulations checks, and we advise before work starts. A written description lets you compare different suggestions fairly.
Frequently Asked Questions
Can a garage roof use a different material from the extension?
Yes. A garage roof is often simpler and gets less use than a lived-in extension, so a different covering may suit. We look at each roof separately and choose what fits that roof.
Should I replace the deck at the same time?
Only if it is damaged or damp. We check by looking and probing for soft spots. A sound deck can stay. A rotten one has to be renewed first, or the new covering will fail early.
Does colour or finish matter?
For the most part it is cosmetic, though it can affect how a roof looks from upstairs windows. The performance depends more on the system, the details and the workmanship than on the finish chosen.
Talk to our team about flat roofing in Brentry
Every roof is different — the fastest way to get an accurate answer is a quick chat with our team.