Leaking balcony flat roof

[Simba_ali]

Hello, 

 

I'm wondering if anyone has any idea about a possible solution to some pretty bad leaks I had during the February storms from a balcony onto a ceiling in a room below. 

 

The leak seems to appear on the ceiling directly under a cavity wall above and runs in lines as if the water is following the joints of the plasterboard.

 

I successfully managed to make it leak by pouring Water directly onto the wall and using a hairdryer to try and create wind. My first thought was that the water for penetrating the brick and flowing down the cavity wall and an apparent lack of weep holes suggest no cavity trays are present. 

 

I tried to narrow it down further by just pouring water directly onto the rubber upstand and not the wall and again it leaked within minutes. My 2 questions I need advise on are 

 

1. Would removing the mortar on the upstand and filling with sealant likely stop the leak or would it require lead flashing over the top? 

2. How likely is it to be water penetration through the cavity wall aswell as a dodgy upstand and would I need to fit cavity trays first. 

 

I'm pretty sure the roof under the decking isn't the problem as it doesn't leak during normal rainfall and only in driving rain / wind. I've attached some photos and circled the lack of cavity trays. Sorry I know question 2 might not be a direct roofing question but any Clues would be appreciated.  

 

Regards 

[PeterW]

Is that a plastic trim over the top of the rubber membrane ..? Doesn’t look like it is fitted correctly, and should have sealant not mortar over the top as it will expand and contract and let water through. 
 

In terms of following the cracks in the boards, water will just flow along these as they are slightly lower than the board itself. Need to find the point of entry first. 

[Simba_ali]

Thanks for the reply 

 

It seems to be some kind of plastic L nosing about 70mm x 70mm that goes into the wall and the rubber material used on the roof has been glued to it.

 

The gap has been filled with mortar which was fine to start with but as you point out it seems to have crumbled away in places and there is visible movement when pushing on the upstand indicating there are gaps behind. 

 

I can pour water directly on that joint (not getting the brick wet) and it leaks after about 5 minutes and falls through the hole on the attached photo which is located below the wall on the outside face. 

 

I'm no expert but my theory is it's literally getting behind this upstand and running down the brick face onto the ceiling below. It seems to happen very quickly and has way to much water to come from water going through the brick work.

 

I've seen a couple of roofers who point out that the upstand needs a flashing but I need a short term fix until I can organise the work and figure out the cavity tray problem. 

 

 

 

 

Edited July 16, 2020 by Simba_ali

[joe90]

As said above it should be sealant (flexible ) not Mortor . I agree that it appears the wall has no cavity tray and no weep vents.

Edited July 16, 2020 by joe90

[Simba_ali]

I know it might be impossible to say but would you say it's more likely to be the flashing leaking Rather that the lack cavity trays /weep holes or a combination of both? I'm thinking of removing mortar and filling with sealant as a short quick fix.  I'm reluctant to install lead flashing first if I need to install cavity trays ..

 

I also have a horrible feeling the weep holes could be underneath the flashing as further down there are unexplained protrusions that I can feel...wouldn't put it past the builders of this place.. ..

Edited July 16, 2020 by Simba_ali

[joe90]

I believe the wonky Mortor is definitely a leak and raking out the motor and replacing with a flexible sealant is a first step, you proved this by pouring water over the joint?. Is the flat roof an addition or built with the house? Only asking as you think the weeps may be under the flashing (can you get your hand up there??).

[Simba_ali]

It's a new build  (4 years old) and was all built as one so that's why I'm sketchy on the details.

 

I can't get my hand up there as the upstand is joined to the roof rubber. 

 

There are definitely weep holes further up the wall and over the doorway so it's strange they would miss them from near the upstand. 

 

 

 

 

 

 

[Mr Punter]

Should be covered by NHBC or whoever

[Simba_ali]

Yea it should be covered but the excess is £1500 and trying to find the exact cause (which they require) will mean tearing the whole roof down plus no roofer can give me a definite answer. 

 

I do plan on using insurance but it's Abit tricky at the moment

[Simba_ali]

 

 

Just a little update....

 

I had a roofer come today and have a look and he says he would  seal the existing upstand with sealant and install lead flashing one brick up over the existing upstand.

 

When i mentioned about the lack of cavity trays he didn't seem that concerned about it as weep holes are present above the door and 4 bricks down from the top of the cavity wall so only a small section has a lack of cavity trays (i'm not convinced by this answer!) He also said maybe putting a brick sealer on the bottom half which doesn't have cavity trays. 

 

I mentioned installing cavity trays and the answer i got wasn't very enthusiastic so i'm assuming its a rubbish job to do!?

 

I've attached a photo of the upper part of the wall where you can clearly see weep holes. 

 

What would you guys do???

[joe90]

Interesting. I agree with sealant and (maybe) lead flashing. I was going to mention brick sealer, I did this on our build as the west wall catches driving rain from the Atlantic not far away, dead easy to apply by brush and when I pointed the hose at the wall later the water ran off the bricks like they were glass.

Edited July 16, 2020 by joe90

[Roundtuit]

I'd be surprised if the rain was penetrating through the bricks.  As above; rake out the mortar and replace with a decent sealant.  I'd also repeat your hosepipe test on the decked area whilst keeping the wall/roof junction dry to rule out alternative routes in. Water will track along any joints and gradients and can appear on the ceiling some distance from the source.

[scottishjohn]

no doubt if where the rubber roof goes into the mortar had been at angle pointing upwards then the lack of adhesion of the mortar to the blue bit would not be a problem 

and any water would run outwards and not inwards 

MY choice would be another flashing set into brickwork as they have done for 1000years 

lead will bond with mortar where as that blue stuff looks very slippy --eg no bond 

 

racking out the mortar and sealer could work --but for how long -would need to non hardening stuff I think 

just my thoughts

Edited July 17, 2020 by scottishjohn

[joe90]

Is the blue upstand 150mm (which is the height it should be to stop “rain bounce”, also can you poke about and find out how far into the wall it goes?

[Simba_ali]

Attached a photo from the deck to the top of the upstand, it goes down even further under the decking. 

 

From what I can tell the flashing goes into the wall by about 3.5 cm. 

 

Would anyone suggest a good sealant? I have builders sealant but I'm guessing it needs to be a special type? 

 

My thought is that I could literally spend thousands on replacing every part of the roof before finding the main cause, so I was going to seal the mortar joints, test with water and if that shows no sign of leaking then leave it until the next storm and see what happens. If it still leaks then I need to look at either lead flashing or cavity trays. 

 

I was also going to hire a plasterer to maybe cut 2 sections of the ceiling out so I can observe any water coming through as so far I have been using a micro cam through the hole in the above photo.... plasterboard is alot cheaper to replace that retrofitting cavity trays! 

 

 

[scottishjohn]

54 minutes ago, Simba_ali said:

From what I can tell the flashing goes into the wall by about 3.5 cm. 

so basically the full width of the brick ?--

or close enough

no wonder its leaking through the wall-and no wonder the mortar has lost grip on it 

sounds like you could lift that wall right off it

do you know is that flashing on top of brick work or a load bearing beam which the wall was then built on ?

 do you know what the flashing is made from?

Is it a GRP right angled section -cos mortar will never stick to that 

Is it a timber framed house with outer leaf of brick?

 

 

 

Edited July 17, 2020 by scottishjohn

[joe90]

1 hour ago, Simba_ali said:

My thought is that I could literally spend thousands on replacing every part of the roof before finding the main cause,

I agree, yes get that Mortor out and replace with good quality flexible sealer, 35mm  is adequate in my opinion. I have used this and it has very good reviews https://www.screwfix.com/p/no-nonsense-lead-sheet-sealant-grey-310ml/21594

Edited July 17, 2020 by joe90

[PeterW]

3 hours ago, Simba_ali said:

Attached a photo from the deck to the top of the upstand, it goes down even further under the decking. 

 

From what I can tell the flashing goes into the wall by about 3.5 cm. 

 

Would anyone suggest a good sealant? I have builders sealant but I'm guessing it needs to be a special type? 

 

My thought is that I could literally spend thousands on replacing every part of the roof before finding the main cause, so I was going to seal the mortar joints, test with water and if that shows no sign of leaking then leave it until the next storm and see what happens. If it still leaks then I need to look at either lead flashing or cavity trays. 

 

I was also going to hire a plasterer to maybe cut 2 sections of the ceiling out so I can observe any water coming through as so far I have been using a micro cam through the hole in the above photo.... plasterboard is alot cheaper to replace that retrofitting cavity trays! 

 

 

 

 

OK so first off, that is a cover over the edge of the rubber roof - you need to take the deck board up, check the board hasn't damaged the rubber too, and take the trim off.

 

Once you have done that, make sure the rubber roof is firmly bonded to the bricks. There are various products you can use for this, Sikaflex EBT+ is as good as the rest and you need a decent bead of it behind the top edge of the membrane so any water that gets behind the flashing cannot get through.

 

Then refit the plastic cover. Rake out the joint and brush it clean, then a good thick bead of lead sealant or EBT+ into the gap and push the trim in. Wedge it downward and then point the gap between the wedges with more sealant and finish it flush. Leave it to dry, pull out the wedges and point the gaps.

 

Leave it 24 hours before you try a water test !

[scottishjohn]

taking what @PeterW is saying as correct , and its sounds right

 

maybe you  should put some more rubber roofing on the legs of the decking boards  so they cannot over time damage the roof by movement  of the decking 

 or another layer laid loose over the first one under  where decking is

 I seriously doubt rubber roofing was ever meant to be a surface to take lots of traffic  or physical abrasion 

 

to repeat from another of my posts  :-

a local hotel had a roof covering  like this next to the beer garden  and crows were bringing food up from the tables to the roof and pecking at it -- to a point where they punctured it

 if crows can puncture it then things on it could also cause punctures

 the roof was redone with GRP

[Simba_ali]

10 hours ago, PeterW said:

 

 

OK so first off, that is a cover over the edge of the rubber roof - you need to take the deck board up, check the board hasn't damaged the rubber too, and take the trim off.

 

 

 

From what I can gather the nosing is plastic and the rubber has been attached to the nosing and glued to the rest of the roof under that decking board so it's all one piece. 

 

There is a protective sheet over the roof rubber to stop the legs damaging the membrane. 

 

I've attached a photo from under the decking where you can see the join line of the roof to the upstand and also the corner of the protective sheet I've pulled back. 

 

Ignore the debris as that fell off when I pulled the decking board up and the protective sheet back 

 

I've had no issues with normal rainfall and I've only seen evidence of leaks 3 times in 3 years and that was all in a 2 month time frame during the Jan/Feb storms this year. 

 

Edited July 18, 2020 by Simba_ali

[joe90]

So if the plastic is stuck to the rubber all round that’s good, best not disturb it, just get that Mortor out and do what  @PeterW says above by wedging the plastic down and filling with sealant. (IMO).

[ProDave]

On 15/07/2020 at 22:30, Simba_ali said:

I successfully managed to make it leak by pouring Water directly onto the wall and using a hairdryer to try and create wind. My first thought was that the water for penetrating the brick and flowing down the cavity wall and an apparent lack of weep holes suggest no cavity trays are present. 

 

I tried to narrow it down further by just pouring water directly onto the rubber upstand and not the wall and again it leaked within minutes.

 

 

 

Then forget anything to do with the wall or the pointing of where the upstand meets the wall.  If it leaks just by pouring water on the upstand, it is a defect in the roof which may be where the upstand joins the main flat roof.

 

Can you remove the deck planks close to the wall so you can see that edge of the roof and any joint? 

 

Then wet small areas at a time until you find where the water is getting in.

[Simba_ali]

14 minutes ago, ProDave said:

Then forget anything to do with the wall or the pointing of where the upstand meets the wall.  If it leaks just by pouring water on the upstand, it is a defect in the roof which may be where the upstand

 

I did think that this could be a possibility so i tested it twice. The first time I poured water on the upstand joint where the mortar is loose and it leaked. I then poured water on the upstand just below where it is bedded into the wall to see if it ran down the upstand and into any hole where it connects to the roof and no water came through. 

 

I haven't managed to check the entire  roof as I haven't yet pulled all the decking, framing , protective sheet and pedestals up but I have poured gallons of water onto the roof and under the sheet and no leaks appear. 

[joe90]

23 minutes ago, Simba_ali said:

I did think that this could be a possibility so i tested it twice. The first time I poured water on the upstand joint where the mortar is loose and it leaked. I then poured water on the upstand just below where it is bedded into the wall to see if it ran down the upstand and into any hole where it connects to the roof and no water came through. 

don’t forget that in heavy rain water will run down the wall then hit your “mortar” bed and find the smallest crack to enter. Even if you fix the mortar joint with sealant and it still leaks, it’s easily removed if you have to fix the whole roof but worth trying first IMO.

[Simba_ali]

9 minutes ago, joe90 said:

don’t forget that in heavy rain water will run down the wall then hit your “mortar” bed and find the smallest crack to enter. Even if you fix the mortar joint with sealant and it still leaks, it’s easily removed if you have to fix the whole roof but worth trying first IMO.

 

I agree, I believe that where I was pouring water on the wall it was doing exactly this. At first I thought it was penetrating the brick but I was never convinced because the leak appears way to quickly.. This would also explain why normal rain on the roof is fine but wind driven rain would hit the wall and run down into the upstand joint.