Weathering on tile hung gable - Builder fail. Ideas please.

[skyblob]

Hi.
My builder has last week completed some roofing work on an extension and I'm not happy with the quality of the weathering. All the rain this week has been a blessing in disguise since it's showing stuff up. One area is detail where a tile hung (plain tile) gable timber wall upstand joins a shallow pitch roof above (single lap tiles above).

Builder has done it like in this picture.

Untitled

• skyblob
• 30 Mar 2010
• 1

Water (wind driven but mostly just surface capillary) is running horizontally beneath the undercloak and entering the ~5mm gap above the top hung tile. From there, it continues along the undercloak till it ends up inside the roof at the rafter, runs down and makes rafter wet.

The Tyvek on the gable is very roughly cut off at the top of the rafter, there is no overlap to the top of the rafter.

Does the undercloak need some sort of drip?
- or is there another normal way to prevent this happening?

I need to get him to re-do the gable so I need a good fix.

 

[freddiemercurystwin]

Its crying out for a nice big lead flashing over the whole lot.

 

[SurreyRoofingEstimator]

Assuming the way you've drawn it is exactly the way it has been done, the reason it leaks could be that the undercloak is under the Tyvek not on top of it thus allowing water into the roof space. The undercloak should also tilt slightly to the outside to create the drip as water won't travel upwards (assuming you have a reasonable overhang of course)

The underlay from the vertical hanging doesn't have to overlap the top of the rafter if that's what you mean there

 

[datarebal]

Sre is correct, but We would have incorporated a neat lead flashing to weather the joint between undercloak and vertical tiling. This does not need to be big.

 

[skyblob]

Thanks guys. Seems my concern is probably justified then.

And SRE, the Tyvec on the roof IS on top of the undercloak as I've drawn it. Not that the water is getting in that way, it's been running along the bottom of the undercloak under wind pressure and capilliary. There is no tilt/drip to the undercloak, it's horizontal.

My builders have said it's "done right" and they'll just add silicone seal to the tile hanging at the top. - Bodge if you ask me, they put a bit too much faith in silicon for my liking, and don't really see the difference between weathering and sealing

Not wanting to undo the (otherwise very neat I need to add) roof, I'm thinking of possibly screwing/bonding an alloy L section to the underside of the undercloak, at least to create a drip. I'll think further on it, but not too happy.

Rgds

 

[justlead1]

Hi. In all areas i have worked it has been standard practice to fit sheet lead cover flashing at the head of tile hanging. This forms weathering and a neat appearance covering cuts and nail holes. However if this is done after the main roof, it would be difficult to achieve success without major work. I have often seen sheet lead bent through 90 degrees and fixed to to batten of vertical work and dressed down over last course and the 1/8th gap caulked with lead sealant. (as would be done with flashing in chased masonry joint)