Fitting Facia / Soffits For GRP Flat Roof

4 Jan 2006
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United Kingdom

I am building a workshop in my garden and have now got to the point where I am waiting to have the roof GRP'd. Before going ahead I need to fit the facia boards.

I have looked at several pics and need some advice on fitting the facias / soffits correctly.
My OSB is already fitted so is flush to the edge of the roof timbers.

1. When I fit the facias should I fit them so the top of the facia is flush with the top of the OSB, or leave them 18mm (the OSB depth) lower so that they are level with the timber that the OSB sits on?

2. The facia boards will be secured to the 4x2. On the sides it will be screwed in to the side of the 4 x 2 but at the front and rear it will be screwed into the end grain. The Facia boards are 175mm which means they will hang down do I need to fit some

3. At the rear end the roof joist only overhang by 20mm will it be ok to just fit the facia board or should I run a piece of 4x2 along the ends of the roof joists and then fit the facia board. This will give me about 50mm overhang at the rear which is a block wall (the back of the shed) Or as the rear will have an arris rail (as the fall is to the front) does it make any difference?

Here is a thread I started some time back asking for advice on the roof timber structure showing part of the construction.

Since then the only changes to the pics is that on the sides I now have a 100mm overhang as I bridged some 4 x 2 along the sides to offer some protection to the cladding that will be fitted.
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