Flat Roofs

Ahleckz

Ahleckz

Ahleckz

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Joined
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Location
Glasgow
A house has come up for sale which looks good but it has a flat roof.

The Home Report is very inconclusive, only suggests that “The roof is in entirely flat and clad with mineral felt or similar. No inspection of the roof covering is achievable from ground level. The vendor advises that the roof covering was renewed prior to purchase of the property in circa 2015.”

When house hunting my girlfriend has been obsessed with roofs and is convinced a lot need replacing. I have never lived in a house and had to replace the roof, whereas her parents have replaced two...
She’s therefore very nervous about a flat roof.

has anyone experience with them?

Assuming it needs replaced, how much roughly would this be?

Would it be worth budgeting to put a sloped roof in (however it’s mid terrace so doubt this is a goer!).

I’ve read some websites which suggest it’s around £3k to replace the roof, and if that was every 10 years then that’s no problem but does seem cheap to me.

but she’s concerned it’ll constantly leak and be cold due to lack of insulation.

So, any thoughts?
 
Depends what you want to replace it with and how big it is...without that info nobody can answer.
 
Dis86 said:
Depends what you want to replace it with and how big it is...without that info nobody can answer.
Click to expand...

Aye, as soon as I posted I realised the size would help.

Roughy 47sqm. No idea what I want to replace it with, just be interesting to see some ideas.
 
I did 3m x 2m kitchen flat roof for £750 with 3 layers of 'high performance' felt. This was in the south east too.

I wouldn't worry. Like you said, as long as it has been serviced it should be fine for 15/20 years.

I oddly have friends and colleagues that seem to have gone through things other people wouldn't even think about at a rate of knots.
 
Ahleckz said:
Aye, as soon as I posted I realised the size would help.

Roughy 47sqm. No idea what I want to replace it with, just be interesting to see some ideas.
Click to expand...

Well, felt tends to be the cheapest and is good for about 10ish years. However, if it's failed then whatever is underneath might need some work.

We use quite a lot of rubber membrane systems which typically come with a 20+ year guarantee. For your size I've just paid the equivalent of 4.5k but that's with a full scaffold and no mods to the underlying structure.
 
Alternatives to 3 layer felt are epdm, fibreglass and asphalt. All have longer lifespans, but are more expensive. Some require maintenance in the form of solar reflective paint every few years.

Flat roofs can be insulated - whether they are warm deck or cold deck.

As said above, cost will depend very much on access, need for scaffolding, and whether the ply underneath is in a good state.
 
Ahleckz said:
Aye, as soon as I posted I realised the size would help.

Roughy 47sqm. No idea what I want to replace it with, just be interesting to see some ideas.
Click to expand...

We have a 42sqm extension in with planning at the moment and my architect recently said that GRP (fibreglass) is roughly £140sqm, rubber single ply around £70sqm and felt is cheaper.

Based in a very expensive area in the South East.
 
I lived in a place with a flat roof for like 7 years before, I didn't own the property but never had any issues with damp/mould/moisture in the ceiling and I know for a fact puddles of water would sit on it for days

I doubt a flat roof is anything to worry about over a normal roof.

won't the roof be insulated with an airgap? so I doubt you will feel any cold even if it's covered in snow
 
Large puddles of water on a flat roof will almost certainly reduce their lifespan. That's why all flat roofs should have a slight gradient on them to direct water off of them.
 
I’m a surveyor and have a natural aversion to felt covered flat roofs.

they cause no end of problems from pooling of water, blistering, solar damage, leaks etc etc.

they are basically a cheap alternative to a decent pitched equivalent.

i fully respect that often a flat roof is a necessity but I would personally not cover one in felt and would use GRP or EDPM as discussed - I would also want to see an adequate drainage system in place in order to negate the possibility of standing water etc

replacing the felt isn’t that hard, it’s the damage to the structure that can be the big issue
 
Very recently moved into an extended victorian semi detached house, extension out the back has a flat roof, as does the loft extension. Loft extension is quite a bit newer than the other.

I aim to get at least the back extension redone with GRP and potentially green roof panels soon.
 
fastwunz said:
I’m a surveyor and have a natural aversion to felt covered flat roofs.

they cause no end of problems from pooling of water, blistering, solar damage, leaks etc etc.

they are basically a cheap alternative to a decent pitched equivalent.

i fully respect that often a flat roof is a necessity but I would personally not cover one in felt and would use GRP or EDPM as discussed - I would also want to see an adequate drainage system in place in order to negate the possibility of standing water etc

replacing the felt isn’t that hard, it’s the damage to the structure that can be the big issue
Click to expand...

Spot on.
 
fastwunz said:
I’m a surveyor and have a natural aversion to felt covered flat roofs.

they cause no end of problems from pooling of water, blistering, solar damage, leaks etc etc.

they are basically a cheap alternative to a decent pitched equivalent.

i fully respect that often a flat roof is a necessity but I would personally not cover one in felt and would use GRP or EDPM as discussed - I would also want to see an adequate drainage system in place in order to negate the possibility of standing water etc

replacing the felt isn’t that hard, it’s the damage to the structure that can be the big issue
Click to expand...
OP read sentence 4 first then all the other bits. Also don't feel shy to knock on the other neighbors :)

You couldn't buy a house where I live if you didn't want a flat roof on 10% of the structure.
 
Thanks guys, sounds reassuring. I’ve booked a viewing for Friday. I’ll ask the sellers but don’t expect they’ll have much to say beyond “never caused us any issues”.

Ultimately I’ve been looking at older properties and always anticipated roof work will be a necessity at some point. Some houses I’ve bid on are 100 years old with original roofs.

it doesn’t sound like flat roofs are too problematic, just need to be budgeted for and keep up to date with maintenance.

I’m glad it’s not going to be £10k every five years!
Gives me a good excuse to buy a drone I guess!
 
if you did replace the roof why not get a loft conversion just saying and while u are at it you could alter the roof to be pitched tiled one.

otherwise if the loft is too much how about getting a quote to change the roof to a tiled one - then at least when it comes to selling u wont have the problems/concerns your seller might have in future plus could drive your premium down a bit for insurance.
 
@Ahleckz if you're happy to do this, would it be possible to trust me a link to the property / photo in the schedule of the roof in question? As its a 47m2 roof thats quite substantial and depending on if it intersects with an existing roof / wall / window this could limit what you can do with it apart from replacing like for like. Depending on the age as well I can give you an idea of potentially what insulation level it may be achieving. Also if its an older property you're looking at if the roof forms part of an extension the chances are its probably warmer than the existing part of the property!
 
Thanks @Derek W , I've sent you a trust. Please don't out bid me!

I think I got my calculations wrong (I was in bed on my phone, so I'll blame that). It's approximately 7.5m long by 5.2m wide. Giving an area of 39sqm.
 
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