How much for a new roof membrane, Victorian 3 bed terrace?

[elmaf]

I think the tiles are okay as several roofers have been unable to identify the problem. So I/they think the whole roof could need a new membrane (several small leaks).

So if they were to use the same tiles, how much do you think the cost will be? Would obviously have to get scaffolding too.

Located in London

This isn't a straight set price I'm afraid. Even using the same tiles (plus it depends on the tiles and how old they are) they would still need to buy some extras as removing a whole roof is impossible not to break some, some are likely to already be cracked or broken but from the ground you can't see etc. and you'd need other materials as well as a membrane plus the roofers labour costs. There may be other issues to fix if you have several leaks. Do you have a standard roof, do you have dormers etc. any windows in the roof? How old is your house?
You need to get 3 roofers to quote for the work you'd actually like done, and try and use recommended ones rather than random Google searches. Also ask to see a few different images of their previous work!

Edited as I missed the Terrace part in the title!

we paid £21,000 for new membrane and new tiles for a 4 bedroom detached in surrey in 2022. We did get a quote to reuse the tiles but thought that the tiles might break if they were removed and put back on. So we just replaced everything and got a building control certificate which cost £400.

My friend wanted this done…the builders all said it was false economy as the tiles would shortly need replacing anyway …..she ended up replacing it all…that said loads of the tiles were damaged when removed so couldn’t be reused anyway…..and the other costs like scaffolding are the same whether you reuse tiles or not…..think her original quote for a membrane replacement only was 7k

Go into the roof in the day. Do not turn any lights on and you will see if there are holes and where they are
because daylight shines through

Not foolproof but it’s the first thing you do if you think there’s a leak

Theres very very rarely a need to fit an entire new membrane
You might want to ask yourself why roofers are telling you this £££

I have done exactly that gone into the roof with a staple gun and a membrane and just covered it from the inside.
Not saying it’s ideal, but it’s not bad
My plan is to then cover it with plyboard
Insulate will do for a long time

As you’ve used a staple gun coating the ply with a waterproof sealant (similar to riw) will offer extra protection from leakage

Don't block ventilation at the eaves.

Roof sealants available in diy shops

I thought the membrane was the secondary protector against leaks? So if there's a leak in the membrane there must also be a leak in the roof?

No
Roof tiles don’t seal the roof
The membrane does

I was quoted about £12k for a fully new roof using reclaimed tiles, 12 months ago (with VAT). My roof measures roughly 8m x 6m, not in London.

Pretty sure old roofs had no membran/felt... Water shouldn't come through the tiles...

Possibly this was before they discovered membrane ?

Dumb question potentially, but which side would you coat the plywood with facing the roof or facing the floor?

They were designed differently
either
the pitch was greater
lime mortar sealed between joints or/and the tiles overlapped more

The waterproof membrane (ie seal) is always on the outer face
so rain is stopped in its tracks
If you seal the inner face the wood will rot before it hits the seal