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Valley gutter problem (Read 691 times)
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Re: Valley gutter problem
Reply #2 - Sep 14th, 2017, 10:36pm
 
The idea that there shouldn't be mortar at all had not occurred to me. Thank you for that thought! I'll look more closely.

Also for the chemical reaction point.

On the relative flexing of the two valleys - actually the one that is causing the trouble probably gets less sun than the other, but possibly more heat from inside the house when the heating is on.

Thanks again.
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woodsmith
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Re: Valley gutter problem
Reply #1 - Sep 14th, 2017, 11:23am
 
I'm guessing the one that is failing is getting more direct sunlight and the expansion is breaking out the mortar, so you could try using sharp sand rather than soft sand as this will give you a much stronger mortar. However GRP valleys don't normally need any mortar; all the ones I have used were designed to be waterproof without mortar. I wonder if the builder has used mortar by mistake and you could just remove it? Ideally you could do with finding out exactly which make of valley you have and contacting the manufacturer to find out if it needs mortar or not. I would be very wary of coating the grp with anything, plastics can react badly with other chemicals and it can weaken them over time.
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Valley gutter problem
Sep 14th, 2017, 8:32am
 
A few years back we had a single storey extension built with a pitched roof at 90 degrees to existing - therefore valleys down each side.

The valleys are some sort of plastic. Each side of the valley has a couple of inches of cement mix packed in above the plastic and below the tiles.

One of these valleys is still largely ok, but for the other one the cement keeps sliding out of place, blocking the valley, such that in a downpour the rain is dammed, pours over the side of the valley and leaks through our kitchen ceiling.

We have had the cement work replaced twice already and are looking for a "third time lucky". How can we bond the cement to the the plastic to keep it in place? Surely this must affect anyone using plastic valleys?

Friend suggested either inserting screws into batten behind cement (assuming there is one!) or stapling rolled chickenwire to same, to give something for the cement to grip to. However, the overhang of tiles over valley makes it too narrow to get any tools in.

His second suggestion was paint bitumen onto edges of valley and push a bit of grit into it, giving something for cement to sit on that would keep it from sliding.

His third suggestion was maybe get some kind of plastic conduit with self adhesive backing and press that onto the sides of the plastic valley, then pack cement in.

What should I do really?!!!

Thanks,

Dumb

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