fascia and soffit detail

24 Jan 2012
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United Kingdom
I have an ambitious plan to build a workshop. It will have a flat roof and I'm considering a GRP covering. I found an excellent YouTube how to for the GRP bit, just need a bit of help with the fascia and soffit detail. My question is what to do when joining the fascia to the roof joists and how to mount the soffit to it. I believe I would need to use vented soffit to allow air movement around the joists and I will only use it on the front and back of the building as this is how the joists are running. There will be no insulation between the joists, the walls will be cavity construction. As far as I remember, the joists will sit on a timber wallplate and be connected with a plate hanger on the internal wall. I will be using uPVC fascia and soffit and tbh, I wondered if there wasn't just some type of venting strip I could use in place of soffit board. Thanks in advance for any suggestions, links to drawings videos etc :)
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I had a similar situation where I did not want to have a large overhang on the sides of a flat roof. I had a standard vented soffit on the front of the roof and it was open into the existing loft space at the back, but the building inspector insisted on cross ventilation from side to side.

I got creative and used some over fascia vents turned through 90 degrees. This gave me a 50mm overhang on the sides.


The inset image in this picture shows how they are usually used.
It took a fair bit of work to get the details looking right though.

For a bit more context and how I finished around them have a look at the 'Flat roof' page on my build blog website which also has some larger pictures.


I'm not sure if it will be suitable for the only ventilation, some of the experts on here could pass judgement on that, but it served my purpose.
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