I took on a house with 40% flat roofs. 2 years ago. It looked ok at viewing and sellers said it had been reroofed.
It had, but by absolute cowboys. I had to have the whole lot reroofed
heres the thing though it isn’t just about flat roofs , it’s about the whole construction. A lot of older flat roofs are “cold platform” ( as mine were). These are prone to a lot of problems due to condensation and are likely to not last as long. You must ensure they are properly built with ventilation. They are very poorly insulated and noise is awful as you’re essential living under a sound box. You’re literally burning fuel into the sky 😱
a modern standard “warm platform roof” is a much better product. The whole design is switched around so the dew point of condensation is now on outside of roof not within the roof timbers and soft insulation as before. You don’t need ventiliation methods. The roof is much more robust with solid kingspan (or whatever) insulation that is meeting modern standards and not pissing fuel into the wind. It’s also significantly better sound wise
so that’s the first thing- find out what you’ve got in term of warm vs cold platform. Cost of replacing cold with warm are very high as I know to my expense. Also needed planning consent and bulding regs
second thing is what the roof is covered with. Historically it was reword bitumen. Ok, cheap to install but life span cheap and dangerous to install- I know someone whose house was set alight as they use torches. Many people have upgraded to fibre glass - better, but on larger roofs can have problems with expansion and cracking . The more modern materials are better like EPDM (think pond liner type material) but can only be used on smaller simple roof shapes due to having to be laid in one piece: they’re way more expensive but have good warentees on them and looked after properly will give years of good performance especially when combined with warm platform structure . Mine is now a PVC , which sounds odd but is a vinyl like structure in appearance. Used in commercial buildings and comes with a stands 15 year warentee and expected,lifespan of 50 plus years . TPO roof materials have similar properties.
all these newer materials must have professional specialist installers and then you hit the next problem which is supply and demand. Took over a year to find someone who would actually do the work and a lot of heartache and stress on the way . Prices also went up during that time , tripled, and I paid a stupid shot load of money to resolve a flat roof my vendors lied about l cost me in excess of £30k.
if converting a flat roof to a sloping roof is possible then that’s something to explore , but it isn’t always possible structurally or from planning consent point of view. Mine couldn’t be converted to slopping roof
id not buy a home with flat roof if I could avoid it . At the time I moved , peak stamp duty and divorce driven, there were so few houses n the market and this was best of bad bunch. 2 years later the stress and worry has ended and I’m happy it’ll outlast me (I’m in my 60s) as long as it’s well maintained.
🤣🤣🤣you might have gathered I’ve become a bit of a flat roof expert since taking this house on🙄😱🤷🏼♀️