new extension recurring roof leak

[masamune]

I have a recurring leak issue with my new built extension roof.

Would appreciate some views before calling the contractor (again) as this is under guarantee.

The roof has approximately 18 degree pitch, interlocked tiles and a flat GRP section just below the 1st floor window. There is also waterproof membrane under the tiles. The roof has two large portrait skylights that have so far presented no issues or leaks around them. Pics attached below for reference.



The leaks started last February following heavy rainfall, damp patches started showing on the ceiling plasterboard below the flat section and also at the lower end near the eaves. The builder brought in his roofer who checked the aprons and lead flashings around the skylights. They reworked some areas, all tiles were in perfect condition.

We thought the issue was addressed but two months later after another strong downpour the damp patches reappeared. They attributed the entire issue down to separation between the fibreglass flat section and the lead dressing over the area meeting with the tiles. I believe this was a plausible cause but I don't know if the work was done as it should have been from the start. On this occasion they brought in a 3rd party roof contractor who worked for a couple of hours and extended the dressing over the tiles and reworked part of the GRP border. The roof was tested for months on heavy rain and we had no issues.

Unfortunately this weekend following 24hours of heavy rain, the ceiling started dripping through a cosmetic crack where the GRP forms a corner with the vaulted ceiling. The extend of the leak is more limited now but it may be a sign the work is prone to recurring leaks. This is quite disappointing since the issue has already been addressed twice. I am trying to understand if the original underlying work of the GRP is problematic and they need to redo the entire job or down to other causes.

I am also unhappy that we need to re-decorate the ceiling due to the patches...

 

[datarebal]

roof pitch to low for those tiles strictly speaking.
tiled verge is not ideal and should have been formed with a flashing over the grp upstand and not relying on mastic
undercloak stops way short which will not help
shouldn't take them more than a couple of hours to adjust

 

[masamune]

undercloak stops way short which will not help
shouldn't take them more than a couple of hours to adjust

When you say the undercloak stops short, I presume you mean the cement boards should extend all the way down to the last tile of the verge?

So this could be rectified based on the existing work and not necessarily redone from scratch?

 

[masamune]

Turns out the issue is with compromising cracks on the GRP or the plausible cause provided by the builder.

I'm waiting for the roofing contractor to come and have a look while the roof is drying. There are "hairline cracks" at the corner of the upstand (I wouldn't really call this hairline)



Either way, it looks like an issue with the original workmanship to me. I won't go into the argument of how long GRP is supposed to last...

 

[datarebal]

Might be, but might not be..interested to see how it turns out

 

[catlad]

I shouldn't hold your breath! they have been back a couple of times already.

 

[masamune]

They revisited the "triangle" upstand from what I could see the next morning. I have not had any detailed feedback but it is pretty obvious.

They've asked to confirm things after the next heavy rainfall, but this does not necessarily mean the issue is resolved long term...

I don't think they used the third party contractor this time, rather they addressed with their own roofer. I may perhaps contact a couple of roofers for an independent view.

 

[masamune]

I am inclined to resurrect this thread as still an issue believe it or not!

After heavy downpour it takes about 15-20mins and the water starts pooling in area of ceiling plasterboard and drips through cracks.

As expected builder did not address the cause of leak and problem kept recurring randomly after heavy rain. I had enough, decided to have grp roof revisited properly and guaranteed. I looked for specialists for a long time, we went from tradesmen who did not even turn up to others who quoted to gain. Quotes ranged from under £1k to £2k for approximately 3.5 sqrm of grp roof. More than one suggested to retain the original grp panel, sand it down, recoat and seal around better.


The quote/work

I went for a local specialist with positive reviews. He was briefed thoroughly of the issue and history. The quote involved sanding down existing grp, extend lead work on one side of roof, re-seal lead work on front of roof, extend side flashing (verve) and finish two coats of liquid rubber (desmopole).

Cost was just over £1k, the work took half day a bit high for labour involved to be honest, but I really wanted this fixed. They also guaranteed work for 20 years, although we know that means nothing.


The result

After 1.5 weeks we got heavy rain and surprise, the plasterboard at the joining corner beneath got damp again and started dripping. I could not believe in my eyes. Clearly no point fixing the ceiling decorations yet with this issue still recurring.

I included a range of recent pics from mobile, link with plenty shared so at least an experienced eye can spot any issues.

https://www.dropbox.com/sh/h5h1zkbo4gfmauw/AABvIvF0C_Ddo89fdKVVQ3lha?dl=0


Revisit #1 (no.5 with old count!)

I called the roofer to come out again, he was responsive and turned up 2 days later. He claimed there was nothing wrong with the grp junction around the pitch roof and needed to investigate. He did not want to go under the pitch tiles, clearly to save cost and hustle to himself.

He said he was going out on a limb and sealed the interlocking line of tiles next to the offending area to test if water leaked in from the interlock (included in my photos link). I found this awkward tbh but someone could comment here. That was a month ago and of course didn't work, as we found out with next rainfall.

I don't think the pitch roof has an issue, leaks would have occurred in other places which has never occured. Another thing is the membrane underneath the pitch at that point as simply not working. For if water comes in pooling at plasterboard below at the corner, it means membrane has either a gap somewhere or failing. I still observe porous areas like holes at the side top/bottom next to last tile and grp upstand, although it's supposed to be all sealed!


I have been chasing up the guy for two weeks now, last time he said he needed to test roof with a hosepipe

As things stand the job failed to address the scope it commissioned for and obviously requires conclusion. In my view he should have looked under the last tile at least to address source of leak, which I suspect he has not done as a saving to himself or so he thought.

 

[catlad]

Well as all ready mentioned by data the ties are under pitched! Something about the window look odd to me.

 

[masamune]

Well as all ready mentioned by data the ties are under pitched! Something about the window look odd to me.

Can you elaborate? Does this apply to the entire roof?

 

[diy_fun_uk]

If it was me (although I appreciate this means more cost and mess) I would remove some of the interior ceiling at and around the offending area (i.e. were you see water marks) to see if that offers any clues. I know water can track in weird and wonderful ways, however if you have someone looking inside (with section of plasterboard removed) and someone outside spraying area with sprinkler to mimic heavy rain, you might gain better understanding of where the installation is failing? It's maybe not a very good analogy, however it's a bit like someone that has a shower cubicle that's leaking. Sometimes, no amount of tinkering on the outside resolves the leak, requiring removal of shower tiles etc to determine exactly where the failed area is.

 

[oldbutnotdead]

Your final pic is a bit interesting- it looks as if they've matted the upstand trim to the wall. Which is always going to fail- the roof should be free to expand/contract, you'd usually use a cover flashing over the upstand of the trim.
Question is now whether there's any clearance between OSB and walls on the rest of the deck and how they've finished the other trims

 

[datarebal]

and the verge is cracked to buggery.. this could be tested by cloaking in some plastic temporarily full length

 

[SpecialK]

What tiles are they? Redland 49?

Minimum Pitch and Headlap - Through coloured 17.5° at 100mm headlap / 25° at 75mm headlap Granular 22.5° at 100mm headlap / 30° at 75mm headlap

Hard to tell from the pictures - Are there cavity trays in the walls above the roofline when there are openings below? Does the staining line up with your existing wall cavity?

 

[datarebal]

They are 49s and it's not 17.5