How much flat roof is too much?!

[Nicole1]

Hi. My husband and I are renovating and extending a 1960's bungalow. We've added a large flat roof extension on the back and are planning to convert the existing garage and add a new integral garage. These are both also currently planned to be flat roof, but that will mean that the property is more flat roof than pitched (even if you exclude the new integral garage).

 

I recently read that this means the house will be deemed "not of standard construction", which may make it difficult to mortgage, to insure and therefore the property value will be affected. I asked my mortgage company to confirm if this is a problem and whether we could avoid it if we pitched the roof on the garage conversion, and they said they can't comment until I remortgage (by which time it'll be too late to change it!)

 

Can anyone advise on whether this is a real concern and whether there is any relevant guidance I can read, or a professional who i could engage to advise (is this something a surveyor would deal with, for example). Many thanks

[SteamyTea]

You could try a few insurance companies, though they may say the same 'not until it is built'.

You could design the flat roof so that you can attach a pitched roof to it later.

May seem like 'double building', but a fake pitched roof may possibly be made to a lower structural standard, maybe @Gus Potter will know about this.

Way I see it is that it is easier to build when you have a structural base to work from, and stand on.

[Gone West]

2 hours ago, Nicole1 said:

Can anyone advise on whether this is a real concern

All I can say is that, when I recently insured my old house, with a new company, one of the questions was about the percentage of flat roof compared to pitched roof on the house. I don't recall ever being asked that question before.

[Mr Punter]

I have has this issue before.  If you can do a pitched roof it will be much better and lower risk.

[Mike]

I'd also go with a pitch roof if you can, provided the flat roof is of no particular architectural merit.

[KA-CT]

An architect or planning consultant is what you need. 

 

From a roofing point of view..

 

If flat, have you considered something sustainable like a green or blue roof covering - Solar perhaps. These can be great living spaces too, in the summer of course! 

 

I would generally always opt for a pitched roof where possible, they're less problematic and more aesthetically pleasing (in my opinion).

 

You could consider a lightweight flat to pitched conversion - there are some terrific systems available these days. 

[Kelvin]

Some insurance companies will have a definition of what they consider to be a flat roof based on pitch. Ours, for example, specifically defines a flat roof if the pitch is 10° or less. Therefore you could look to see if you can increase the pitch above 10°. It also notes what percentage of the overall roof is flat with the minimum point being 33% and the band is noted as between 33% and 50%. It doesn’t really explain the significance of being outside this band i.e. no loading below 33% or won’t insure/more loading above 50%. Therefore again what percentage of the overall roof will be flat. It also stipulates that the roof must be inspected every 10 years by a qualified roofer (doesn’t state what they mean by qualified). Our insurer is Home Protect underwritten by Axa. It’s quite dear but our house ticks all the wrong insurance boxes. 
 

I would ask the lenders and insurers for copies of their terms & conditions and see if there are some common dimensions/metrics and then look to fall outside of them if possible. 
 

Our last house had a large flat roof (more of a lean to) but the pitch was greater than 10° and it was 15% of the overall roof so it was never an issue. 

Edited 21 hours ago by Kelvin