I built my two storey extension for 20% of builder's quotes

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Fitting grp Roof Valleys

Back up the scaffold tower for yet more work on the roof!

I now had to create the valleys between the old and the new roofs. As I have two new roofs cutting into the old roof, this would mean the creation of four valleys.

I would be laying 'Rosemary' plain tiles. Often, people use special valley tiles that are curved to make a seamless tile roof. However, these can only be used where the pitch of the two roofs is the same. Where the pitches are not the same the batten spacing runs out of sync.

The pitch of the old and new roofs were close, but not the same, so I would have to create open valleys instead.

valley_boardOpen valleys can be lined with lead or GRP, but both systems require support boards beneath as they are not sufficiently well supported on thier own.

I used 12mm marine ply laid between the rafters, and supported on timbers. The GRP valley manufacturers have good installation details with their product.

Cutting the boards at an angle to fit between the rafters was a bit of a pain.

Valley support boards laid up one side of the first valley.

I still needed to cut back the old battens so that I could lay boards up the other side of the valley too.

valley_boardsIt's all rather time consuming and awkward, unfortunately. And this was just the first of four valleys.

I marked and cut the bottom edge of the valley so that it terminated into the gutter. Some brickwork needed cutting back to allow the valley to run straight to the gutter and not be kicked up. For those with fascia boards, it will be these that need cutting back. Again, the product manufacturers offer good detail on this, check their websites.

I fixed the GRP valley down to the battens. First valley complete. I then repeated the process again, and again, and again.



The rains came during this period of the roofing, so I tried really hard to push on, fed up with rustling tarpaulin and rainy ingress. Unfortunately, this meant my photography duties were slightly neglected. This picture from Harcon clearly shows how to install the valleys, however.

I bought pre-made GRP valleys. I had considered lead, the traditional material, but decided that the GRP offered advantages. The installation instructions advised the use of two battens running the length of the valleys. I pushed the GRP valley snuggly down into the valley boards and marked where the battens should run.

I then laid a sheet of roofing felt along the length of the valley and nailed the battens in position. The GRP valley would now push snuggly into the valley between the battens.