Flat Roof Replacement Cost
Prices and guide for flat roof replacement
Constructing a flat roof is quicker and cheaper than a traditional pitched roof, flat roofs require fewer materials which they cost much less to install. they are also much simpler so are a better choice for DIY enthusiasts. But the big disadvantage of a flat roof is the potential for water and other debris to gather which over time will cause the roofing material to degrade and eventually leak, even though they are in fact built with a slight incline. This means that flat roofs also need a lot more maintenance than a pitched roof to keep them leak free and in good condition, but even with all the maintenance, they only last around 10 to 15 years.
To be watertight flat roofs need to be covered with roll asphalt, EDPM, uPVC, ethylene, TPO, fibreglass, modified bitumen membrane or flat-seamed metal. Although repairing or replacing a flat roof could fall within the scope of an experienced DIY enthusiast, most of us will need to hire a tradesman to do the work for us.
Typical flat roof quotes
Things to consider
With flat roofs, you really need to get a roofer out to inspect the roof before giving a quote, as it can be difficult to assess the condition of the timber underneath the felt, without getting up on the roof and physically checking it. Though some roofing contractors will be happy to give you a separate quote to replace the wooden decking over the phone so you know how much it could cost in the worst place scenario. If the wood under the felt is in good condition, then this is obviously good news as it will reduce the costs of replacing the roof. But if the wood is rotten and sagging, then fitting new felt onto a rotten base is obviously not a good idea. Another point to consider is that flat roofs should have a slight slope so that rainwater will run off the roof and into the gutter.
If the roof were actually completely flat, then water would simply pool on top of the roofing felt, which would shorten the life expectancy of the roof. So if replacing a flat roof, get your roofer to check the existing roof and consider raising one end of the roof a couple of inches higher if you have problems with standing water in the past. This will, of course, involve some additional costs, but should add many years to the life expectancy of the roof so will normally be worth the extra cost. Stones and chippings are “extras” that can be placed on the top of the felt, these used to be necessary to protect the felt from UV rays, but modern felt is somewhat UV resistant in any case, so you do not need to put stones or chippings on the roof felt, but you can if that’s what you prefer.
If replacing a flat roof above a habitable part of your home then you will need to make sure the existing insulation is in good condition, actually, if the roof is very old, you should probably ask the roofer to quote for additional insulation and add it to the project.Sometimes it may be possible to repair a roof rather than replacing it. If the majority of the flat roof is in good condition but there are cracks/leaks around vulnerable areas such as where the felt joins a wall, then a repair may be possible which will obviously cost considerably less than a replacement roof. But if your roof is leaking because it’s old and has multiple cracks, or if you can see rainwater pooling on the surface and the roof is sagging, then repairing it is not a long-term solution, just a temporary bodge job!
Doing it Yourself
The first signs of trouble with a flat roof are often damp patches or water dripping from the ceiling in the room directly below. But before you climb up and have a look at the roof, think about the strength of the flat roof and whether it could be rotten and dangerous. To be on the safe side, you should probably hire a professional roofer in the first instance to inspect your flat roof safely.
A professional roofer can quickly inspect the condition of the flat roof and find any tears, puddles, holes, cracks or splits. Plus not all roof leaks are due to a roofing problem, blocked guttering or downpipes around the edges of the roof can also cause roof leaks. Poor repairs to a flat roof can be dangerous and cause structural problems down the line, it is important with all roofing work that repairs are carried out correctly. While a complete flat roof replacement maybe Breydon the skills of most DIY enthusiasts, patch repairs to a flat roof are pretty straightforward.
Blisters can be eliminated by using a heat gun and some bitumen adhesive, then applying new pieces of felt overlapping the repaired area. Splits and cracks can be repaired with adhesive after being filled with bitumen compound and flashing problems can often be solved using self-adhesive repair tapes after thoroughly cleaning the surface.
Flat Roof Replacement Checklist
- Flat roofs are cheaper and quicker to install
- Flat roofs can be made of felt, asphalt, fibreglass, rubber or single ply membranes
- Most domestic flat roofs use layers of bituminous felt for weather proofing
- A professionally installed flat roof has a lifespan of over 20 years
Hiring a Tradesman Checklist
- Always get at least 2 quotes before hiring.
- Never pay the full amount upfront.
- Get the quote in writing.
- For any payment you make, always get a receipt.
- On more expensive jobs, ask for references.
- Check if the tradesman is a member of any trades associations.
- Make sure the tradesman has public liability insurance.
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My flat roof is leaking, can it be repaired instead of replaced?
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I need to replace the roof of my shed.
Submitted by Naliniben
Cover flat roof with new corrugated sheets Size of roof 11M X 4M
Submitted by Ray
Replacement of roof asbestos wants to be taken off and replace with whatever is needed.
Submitted by Shirley
Flat roof replacement for a single storey extension of about 2x.2.5 metres. It is on a property I am in the process of purchasing and has come up as a concern on a homebuyers survey.
Submitted by Georgina
Replace the existing flat roof above a bay window first floor and fit a rain gutter.