Advice flat roof v pitch roof on new extension

[dontcallmelen]

Hi we are in the process of getting quotes for a smallish side return extension, 2x4mtr two quotes both saying flat roof with lantern rather, than a pitched roof, as the drain from upstairs bathroom would be much easier & cheaper to route over & down roof, rather than box in/access hatch inside the the room, also would be a cheaper build if we went with flat roof.
Does anyone have any advice/experience of a flat roof or should we go for the more expensive option?

My builder always says that there are only two certainties in life: you're going to die and your flat roof will leak... We have a flat roof across the back addition and had a resin roof put on it which has a much longer life so it might be worth considering that as a solution.

We have a flat roof over our double garage, utility room and car port - and it needs reroofing every 10 years or so - so you should factor that cost in if you plan to be in your house for a reasonable period of time.

I really dislike our flat roof as it looks ugly, and we will be putting in for planning permission to either extend above it, or if not permitted to put in a pitched roof.

Not sure if it's related to the flat roof, but our utility room is freezing in the winter, and there's no room to put insulation above it due to the flat roof - but that could just be the poor build at the time (about 30 years ago).

We've had to have a flat roof on our extension as it was too big to allow for the gradient of a pitched roof. So we've decided to have a green roof which hopefully will look nice, and won't leak?! It has a special membrane, and it will provide a degree of insulation, as the house is south facing, I was worried about the kitchen being like a greenhouse. Having said that, if it fits and any boxing in looks ok, I would have a pitched roof as it won't need doing again for many many years!

We recently had to replace a flat roof. In its entirety. (Had not been maintained at all.) Opted for pitched. Roofers were all unanimous that much less work required in long-run. (We'll be here a while.)

Pitched if you can. We have flat roof with a very large lantern (3 x 5 m) and even with the best of intentions the flat roof "ponds" making drainage less than efficient. With a pitched roof you could have roof lights that are minimal in profile but let in a lot of light. We have heritage ones elsewhere in the house which suit older properties. I think they are from The Heritage Rooflight Company. Not cheap but are an excellent product. If you do have to go flat make absolutely certain that top class materials are used and pay great attention to how it is constructed to minimise future problems. They should not have problems after 10 years if they are constructed properly and the drainage works.

I would always go for a pitched roof over a flat.

Thanks everyone flat roof would, be well insulated & finished with rubber no seams, but just not convinced it would last as, long as builders say.
Have asked them to quote for a pitch roof, which will add extra expense due to drain/manhole issues, been a bit shocked at quotes but like everything prices have increased, will be interesting to find out how much price increases.

We had an extension last year and had this dilemma. We ended up with a pitched roof and I'm very glad. Our Next door neighbour (attached as house is a victorian semi) has done the same but with a flat roof. She has puddles on her new grp flat roof whilst we dont and we have a lovely internal space with very interesting ceiling shapes with our pitched roof (hers is boring). I've also noticed that her roof blocks the upstairs bedrooms view of the garden compared to our (lovely) ) pitched roof - there is still a big of a garden view upstairs

*bit

Pitched roof every time
even if you have to go with an odd half hip design

you often see people putting pitched onto flat
rarely the other way round

Marmite - never thought of that, this is a Victorian house too, the middle bedroom does have a good view of the garden.
I can understand the builders suggestion of the flat roof option ie speed/cost but,I think will regret not going for the pitched roof, so going to bite the bullet & hope the quote, will be still doable.
Many thanks for all your replies.