New flat roof on top of existing?

[velliel]

Hi - Original builder moved to Australia. he did us a single storey extension 2006. It has a warm roof and felted (3 layers by a roofing company he brought in). Nice job, looks good! However, ever since we get a large area of pooling that sometimes covers over half the roof and sits for days. Not much water reaches the gutters. As far as we can tell, there are no leaks at the moment, but I'm concerned for the future.

Internally, small separation cracks between ceiling and walls (where the roof meets the original building - the free side is OK). This could, I suppose, be settlement or poor construction originally. Have filled these twice already but opening up again and looks messy - I'm planning to cove this out, but want to make sure the roof is OK first and leaks at the edge not the cause of the problem.

Had a guy in who thinks the internal cracks caused by weight of the water volume creating slight movements over time. Sounds feasible. He thinks the fall on the roof is not great enough - I tend to agree.

His plan is to build a new roof over the top (without stripping out the existing roof which seems watertight) - new firrings to increase the fall, deck and felt(two layers, the top one being fairly thick). We already have parapet walls etc to work from. Pricing this at £3,800. The area is approximately 3.6m x 7.7m

Is this a reasonable plan?
Will it compromise the thermal issues from the warm roof?
Is this a reasonable price?
Would this be covered by building regs?
Any questions I should be asking?

Thanks for your time guys.

 

[foxhole]

Seems expensive to me, my similar sized flat roof cost less than £600 to cover with epdm , but was a diy job.

 

[Xenon]

£135 a M2

Is it 20 storeys up ?

Thats about a £40 M2 job tops.

 

[velliel]

Is it 20 storeys up ?

Ha - no it's a ground floor kitchen!
Emailed building control and had a response to one question direct from the horse's mouth

regarding formation of a new roof above an existing flat roof, I can confirm that the works will require a formal application under the building regulations, the feasibility of the proposals can be assessed following the submission of the application. Given the nature of the proposed works a building notice application would be acceptable.

So, they won't tell me if this is a sensible thing to do unless I hand over the dosh.

 

[alan333]

Depending on how big/deep your pool of water is, there's a couple of ways you could help it (assuming it's felt on top, not chippings) without spending mega thousands.

First way is to pour hot bitumen on the roof to "fill" the pond, then lay a layer or two of felt over it as necessary. This will only level the roof off a bit tho, so the water will disperse to all sides of the pond, not just towards the gutter.

Next way achieves similar to your roofer's firring method, but using different thickness boards. Start at the fall (gutter edge) and lay no boards. Then lay half inch boards for the next metre or two, then inch boards for the next bit, and so on. This achieves a fall towards the gutter, but still won't work if, for example, the pond is two inches deep and at the high end of the fall. Obviously this way would also need to be felted over too.