leak from flatroof - options?

[unwashed potato!]

we've had a minor leak from our flat roof for years, never been a major issue as it happens infrequently (about 5/6 times a year), and it happened in what was a car port, then a utility, but now it's been converted into a second kitchen for our tenants to use and so is more of an issue now for us to sort.

the flat roof is of weird plastic membrane material (almost like a really thick black bin bag) rather than felt. we've tried painting on this very thick grey "paint", which seemed to work for about 1/2 years, but it's leaking again, and i've tried to repaint it on this weekend, however the leak is still happening and the roof is rather slippery at the moment so it was hard to get it to stick, even doing a clean before hand (limited to how much i did due to the poor weather)

i'm looking for advice as to what else we can do now.

the ceiling in the 2nd kitchen is wood planks, and we've taken down a few in the spot it leaks. you can see the water runs directly down the beams side that's directly above the wood planks, however above that is what looks like chip board and you can't see the water source there and obviously water can run along anything to find this spot. it should be said that directly above the leaking spot is the join for a few of the plastic membrane where they all meet. this initially led me to believe it has to be the spot where the leak is coming from, but i have painted so much of that grey paint on this spot over the years you can't see the membrane any more.

i'd rather not take the whole stuff up and start again as the area is large, with it covering out kitchen, WC, study, large garage and 2nd kitchen.

any thing you can suggest i could try to try fix this?

i'm considering putting something above the ceiling wood planks to try and catch the leak before it gets all the way through, and then redirecting that else where, though no idea where

 

[darkblade]

Flat roofs have a short (compared to pitched tile) life span (~20-25 years) before they need taking up and redoing.
Reality is you're going to have to bite the bullet and get the roof resurfaced, otherwise it's just going to get worse and you are just going to be plugging leaks every 6-12 months from here on in.

 

[Uhtred]

My parents had two leaks from their flat roof, and both times it turned out not to be the roof itself to blame.

The first leak was because the DPC was bridged and water was going all the way up the wall, then across and dipping down.

The second leak was worse, and they even had the roof replaced in an effort to fix it but it would still leak during heavy rain.

It turned out that it was the wall causing the problem because the builder had used capping stones instead of coping stones (coping stones overlap the brick giving it protection) and over the years water found its way down the wall

It probably doesn't apply here but i'm just saying keep an open mind

 

[unwashed potato!]

It probably doesn't apply here but i'm just saying keep an open mind

Well that is my concern. Viewing from above, there's no reason this should be leaking in this spot.

 

[alexakasloth]

Is the paint creating a good seal? I have found stixall to be very good for external sealing, as well as sikaflex (291).

 

[unwashed potato!]

Is the paint creating a good seal? I have found stixall to be very good for external sealing, as well as sikaflex (291).

From what I can tell yes. I'll try get a photo when I'm next brave enough

 

[Deleted User 298457]

Sounds more like a guttering problem.

 

[unwashed potato!]

Sounds more like a guttering problem.

How so?

 

[Mel_P]

What you probably have is EPDM (from web - You can expect your EPDM rubber roof to last for 50 years or more. This is thanks to continuing innovation in the manufacturing of EPDM membranes. The material is not susceptible to damage from exposure to UV light such as shrinkage, nor will it rot or be damaged by precipitation. Rubber roofs are also shear resistant, and able to withstand high winds.)

The material is good - but if it gets puntured or split by movement of its support it could still leak. It neads to be sealed at overlaps as well. It is quite thin compared to felt but longer lasting.

Suggested that silicone selant is used for overlaps "See how easy it is to repair a leaky seam on an EPDM Rubber Roof. Super Silicone Seal is a game-changer. It bonds to EPDM and Torch Down Rubber and makes for an excellent leak repair. You don't need to be handy to make these leak repairs on flat roofs."

Mel

 

[~Divine~Wind~]

Aye EPDM as above, normally lasts a while as long as its not damaged or installed by chimps

You could go full on ghetto, mix some black colouring into PVA and just douse the area with that for a temp fix

If you find any like punctures or owt a blob of CT1 will protect it from anything upto larger meteor strikes

 

[Hawk Tuah]

I've spent the last two years trying to fix a leaky flat roof that from above resembles a 2m2 fish pond with a hole in one corner.

This winter it looks like I've finally achieved it as I've not had anything through despite the heavy rain.

I went over the whole roof with a couple of applications of fibreglass resin. Seems to have done the trick.

 

[unwashed potato!]

I've spent the last two years trying to fix a leaky flat roof that from above resembles a 2m2 fish pond with a hole in one corner.

This winter it looks like I've finally achieved it as I've not had anything through despite the heavy rain.

I went over the whole roof with a couple of applications of fibreglass resin. Seems to have done the trick.

To be fair it's still only mid autumn but I get your point. I should have done the same in summer but as last year was mostly OK I was lazy with it. Now I'm dancing on ice up there trying to figure out what's wrong.

 

[Deleted User 298457]

How so?

Infrequent leaks -- I had exactly the same symptoms. Basically when it rained sufficiently the water was overflowing and battering a bit of the roof where pressure made all the difference (was the join between wall and extension in my case).

No amount of sealing what you have will work if the volume of water is exceeding the design intent of the roof.

I had the whole roof replaced, then spent 700 quid on flashing which was an absolute nightmare as the clown took 3 attempts then replaced the whole roof (which he also cocked up lol).

Anyway one night it rained bad and I just ran out and observed and it was a blocked gutter all along. No amount of messing with the roof (other than going like a foot up the wall with tanking or lead) would have helped.

 

[Noakesy85]

We've had a very similar problem to OP, our Bay Window used to leak like crazy during heavy rain and nobody could figure out why. We had a roofer replace all the flashing on the Bay window, he even checked the roof for us to make sure that was all good (and it was). After a lot of headaches I ended up going up the ladder and running a new bead of silicone around the window frames and painting the rendering across the front of the house, this seemed to stem the problem. That was 10 or 11 years ago now.

Earlier this year our tenants complained of a small leak coming from the Bay window again but then wouldn't allow anyone in to investigate.

We had a friend go round to the property yesterday to do some landscaping and gave him a key to keep warm and to dry out. He also noticed a leak coming from the window which says to me the fix I put in place all those years ago may have started to fail. So next time I'm back up in Norfolk (maybe in a couple of weeks) ill be taking my ladder and some sealant for the windows and some paint for the render Hopefully my house hasn't flooded by that point.