does anyone have any ideas how fix a venalation problem i have with my cabin roof wich is a flat shed style with a 1 to 2 slope,top and bottom is sandwiched tight to the joists with no room for air movment,soffits are closed with ply.any thing short of tearing off top and redoing the roof?
thanx
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Any insulation in the roof? Is it between the joists, and if so, how thick is the insulation and what size are the joists?
yes there is insulation inbetween 2x8 joists 12'' oc,poly on warm side
Why do you think you need ventilation? What is the problem that makes you think this?
sorry i should have told you about the ice daming in the winter,with no ventilation im sure the joists are rotting or will start.their has been sagging before that i corrected already but the main things ice daming which in turn produces leaks.
You have a number of options. I will give you them in order of high effectiveness/ high cost to low effectiveness/low cost.
1-Build up the roof creating a vent space between the old sheathing and new sheathing. Install new roofing over the new sheathing. You can also add foam insulation at the same time if you wish.
2- Cut vents into the soffits and add a vent to the ridge. To be at all effective there will need to be an air space over the insulation. If access to this space is difficult or expensive, the first option may still be the best.
3- Shovel snow off the roof. This is obviously cheap but you need to do it soon after a snow fall.
thanx for your input,i think the 1st suggestion would be the way to go.but dont you think i still would have a moisture problem in the old roof still?i.e. moisture from the kitchen,shower,wood stove (with metal buckets of water on it for hot water)and also since the insulation is tight the moisture created from a warm zone(bottom)and cold zone(top and underneath new roof).now you mentioned putting rigid foam in new roof,would that turn the top of old roof into a warm zone now and act as a whole unit?
You should really investigate foaming it. It will seal the heat from inside from melting the snow on the outside or maybee try using a steel flashing for he first 3 feet of roof snow generally doesn't stick to well to the steel
It is possible to pump enough water into your house to create a moisture problem. We have sealed up a swimming pool room with an elaborate system of foam and foil that was rolled out and caulked at the seams. This was furred out with 2x4's that were caulked at all the fastener points. I expect that five years from now we will get a call saying that all the rafters are rotting out. Obviously you should try to control sources of water vapor.
If you add foam insulation to the top of the roof, this would be on top of the original sheathing. On top of this you would add 2x rippings running from the eave to the ridge. These rippings create a vent space and the cold roof. On top of these rippings you would put solid sheathing or skip sheathing depending on your roofing material. You would need to cover up this system on the edges with a new fascia which would incorporate a vent at the eaves.