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Author Topic: Leaking roof  (Read 297 times)
DonL
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« on: February 22, 2021, 05:44:05 PM »

We got PV installed on the Parish Hall roof some years ago and have experienced an intermittent leak of rainwater into the hall in one location ever since.
The panels are mounted onto Unistrut which is mounted from anchors which were drilled through the fibre cement slate tile roof into the rafters and then have a rubber collar which is screwed down to form the seal. The "slates" are 300mm by 600mm and overlap as they should.

The panels have been off for two or three weeks now and despite heavy rain have not leaked. Previous leaks seem to have occurrred when there is heavy rain. The leak occurs on one particular rafter with four anchors on it.

I cannot see any broken tiles or loose seals.




My only theory is that the particular anchors which seem to leak have been drilled through quite near the edge of the tile and quite low down on it so that water going down the joint between the tiles can infiltrate across and go through the hole in the under tile.

If this is the case I am toying with the idea of running mastic down the joint at the side of the tile from the tile above so that water cannot infiltrate across.

Any other suggestions would be helpful and what type of mastic would be best?

This is the second time we have had the panels off and we have to scaffold each time so help would be appreciated.

Thanks

Don
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Schuco solar hot water - 3300kWh/annum, 16 BP 4175N PV panels - 2.8kWp, log burner and back boiler and 18 Ying Li 235 PV panels - 4.2kWp, 42kW ground mount PV, 9kW Panasonic ASHP, 40kWh Nissan Leaf
Iain
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« Reply #1 on: February 22, 2021, 06:33:17 PM »

Hi
Can you slide in a strip of DPC, or a thin copper sheet under the slates to lay under the join in the slates. If you use copper you could fold the 2 sides over to form a fold back? (copper from old copper cylinder??)
Slide up enough to go under the slate above and also under the head of the rivet/tingle by a couple of inches
As per the picture hopefully!!

Folded like this, a bit neater though and with a bit more precision!!


Iain


* IMG_6495.jpg (113.92 KB, 999x663 - viewed 118 times.)
« Last Edit: February 22, 2021, 06:38:34 PM by Iain » Logged

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20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - P3 Amita Lithium Battery
9000ltr rainwater storage   Plymouth
Philip R
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« Reply #2 on: February 22, 2021, 11:13:59 PM »

The roof sealing arrangement looks remarkably similar to the way some close coupled toilet cisterns are fastenned to the pan below using fasteners passing through holes in the base of the china cistern, The manufacturers provide coach screws, penny washers and rubber washers. I have used plumbers "bodge-it" compound ( silicone bath sealant)  to make this water tight, otherwise the water pours out the wrong way.

I believe the rain water is seeping under the rubber washer and through the hole in the tile.

My suggestion is to unscrew the assembly and lift the rubber washer off the roof tile. Clean it all up, clean rubber washer or if split, replace with new or if not availible, a rubber washer i.e. 3/4" tap seal washer. Apply some silicone sealant top and bottom of rubber washer and reassemble bracketry.
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Iain
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« Reply #3 on: February 22, 2021, 11:38:52 PM »

Hi
Another look at the picture and the seal doesn't look too bad on the top of the slate. Looks like the water is going under the slate withe wind and then down the unsealed hole in the bottom slate.
One way possibly, if you can remove the fixing, get some soft neoprene seal and put under the slate where the fixing goes through. Put the fixing back in and it will go through the new bit of neoprene. The top seal and nut will then tighten and squash the new seal between the slates. Or if you don't want to take the fixing out, just slacken the nut so the top slate will lift a bit and then gun silicon or mastic under the top slate around the fixing. As it all tightens down the sealant will spread and totally seal around the fixing between the 2 slates.

Iain
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1.98kWp PV (11 x Sharp 180 and SB 2.5)
20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - P3 Amita Lithium Battery
9000ltr rainwater storage   Plymouth
DonL
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« Reply #4 on: February 23, 2021, 04:39:58 PM »

I really like that Ian, I was a bit dubious about the first proposal because the use of DPM possibly didn't make much difference and the copper might tend to disrupt what are really quite well fitting tiles. I think the top seal on the fastener is really quite good and as the leakage only occurs in strong winds it is more likely to be going under the top slate.
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Schuco solar hot water - 3300kWh/annum, 16 BP 4175N PV panels - 2.8kWp, log burner and back boiler and 18 Ying Li 235 PV panels - 4.2kWp, 42kW ground mount PV, 9kW Panasonic ASHP, 40kWh Nissan Leaf
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