Exterior foam on wall above roof
I’m nearly done with a major reroofing effort. This included fitting a TPO low pitch roof, and recycled TPO synthetic slates. Now we are going to fit 4″ of XPS on the dormer above the roof with TPO membrane and above an area with synthetic slates (this wasn’t in the original plan).
So here is my question:
Normally you would stop the 4″ of XPS before grade (to stop insects getting in), but in this case what is below the XPS is a TPO membrane roof, not dirt. So when fitting 4″ of XPS where what is below the XPS is a TPO (30 year+) membrane should the XPS and (vinyl) siding, come down to meet the TPO, or should it stop short a few inches.
The roofer would prefer to run the XPS down to about 8″ off the TPO deck. My preference is to run the XPS and siding right down to the TPO but make sure that the 3/4″ ferrings are screwed no lower than 10″ from the deck (to avoid punching the TPO that is lapped up the sheathing).
thanks
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Replies
Hey Mark,
I can not answer your question
I was thinking about you and your kitchen soup experiment yesterday.
I made some toast....put it on a paper plate on top of a stone countertop.
Vapr drive from the hot moist toast blew right thu the paper plate and condensed on the cold stone countertop.....any way that's my kitchen experience.
Mark,
Bring the XPS right down to the existing roofing.
Then flash the XPS that will be exposed with metal flashing (to prevent UV light from causing deterioration of the XPS).
The vertical strapping (furring) should stop 8 inches short of the existing roofing, as should the vinyl siding. Install insect screening at the bottom of the vertical strapping.