Garage roof - water tracking back - advice needed

[xcentric]

I have a garage roof that has a shallow angle of slope on it, made from Excelclad (the metal sheets with angled corrugations). It's great stuff, but at the rear of the garage, where it overhangs the gutter, the water doesn't tend to drip down into the gutter but instead tracks back up the sheet until it reaches the joist across the back, whereupon it runs down both sides of that and so makes the top of the wall damp/very wet.

Possible solutions:

• bead of silicone along the underside - tried that, but doesn't seem to make much difference - am guessing capillary action sometimes assisted by wind means it doesn't work.
• foam shaped inserts - these help, but water seems still to track through them a bit, and by blocking up the gap the ventilation there will be removed/much reduced, which long term is not ideal (especially if roof is boarded over underneath which is the plan).
• expanding foam - would work, but again I have ventilation concerns
• long thin strip of roofing felt between joist and roof, overlaying gutter edge (like flashing, essentially) - would connect the lower bits of the roof better to the gutter, and leave a space where the higher parts are for ventilation (and most of the water seems to come in on the lower parts) - disadvantage is it means undoing that part of the roof, feeding in the strip, and then refastening - ok, but a bit of a pita
• ignore it - once inside is boarded, it will drip down between walls and then evaporate.

Anyone got better ideas?

[Mr Pointy]

xcentric said:

Anyone got better ideas?

Yes, a picture is worth a thousand words. Put a couple up to show the issue.

[PositronicRay]

How about making small cuts in the end of the sheet, and bending to form a drip strip?

[Aluminati]

Strip of Butyl tape on the underside. Sheet will need to be spotless to achieve a good bond. Decent outside temp required also.

[xcentric]

General picture showing roof and water


Up close looking outwards - you can (just) see the silicone bead on the upper part, but it extends all the way along.



The grey flock is anti-condensation coating - as this roof was made from spares, not all sheets have it hence the plan for an interior ceiling and insulation to stop condensation dripping.....

[Aluminati]

PositronicRay said:

How about making small cuts in the end of the sheet, and bending to form a drip strip?

If it’s a coated sheet this would cause what is known as cut end corrosion. Wrecks the sheet.

[pquinn]

Get some eaves protector plastic trays and stick those along under the edge? Maybe with a sealant strip between them and the roof, like maybe an EPDM seal strip stuck to the top of the eaves tray.

If the anticondensation coating is wicking the water back from the end you might want to paint over the outside edge with something to seal it?

[Gingerbread Man]

Get some sheet metal pliers and bend the ends down at an angle. Typically designed for bended the rear of the sheet up to stop blown water tracking under the flashing and down the back of the sheet.

[xcentric]

keep the ideas coming! Not sure the pliers will work as the corrugations mean there would be complex folds.....

[Daggle74]

Would something like this work? Either fill the gaps in with it, or place it the other side of the wall and mastic it to the underside of the sheet?


https://www.cladco.co.uk/fixings-and-accessories/p...

[Gingerbread Man]

xcentric said:

keep the ideas coming! Not sure the pliers will work as the corrugations mean there would be complex folds.....

Just get it done mate.

[xcentric]

Daggle74 said:

Would something like this work? Either fill the gaps in with it, or place it the other side of the wall and mastic it to the underside of the sheet?


https://www.cladco.co.uk/fixings-and-accessories/p...

Tried that and it helps but then don't have vented roof space, so moisture that does get in isn't cleared out so well.....

[pquinn]

If you wanted to do the expanding foam thing but still want the ventilation it would be easy enough to stick some round conduit in the gaps first to keep them open & drip proof.