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grover
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# Posted: 2 Sep 2013 10:20pm
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I'm getting near the stage where siding will be installed and I'm trying to find the correct way to do it. I would like to go with cedar 8 inch bevel siding. I have 2 x 4 walls with osb sheathing and then house wrap. I will probably insulate with R13 or R 15 fiberglass.
Some recommend installing vertical furring strips to leave a gap between the house wrap and the siding. I think it is called a rain screen. It allows moisture from inside the house somewhere to escape.
Is this the best way to do this or does it depend on the area of the country you live in?
I was going to nail the siding directly to the house with no air gap.
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toyota_mdt_tech
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# Posted: 2 Sep 2013 11:21pm
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We get plenty of rain and they it goes "OSB, Tyvek and siding"
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MtnDon
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# Posted: 3 Sep 2013 01:17am
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Quoting: grover I think it is called a rain screen. It allows moisture from inside the house somewhere to escape.
Yes, it is called a rain screen wall. The air space is an aid in allowing moisture that passes from the interior out to the exterior in a safe manner. If there is no air space the water vapor may condense and soak into the wood siding.
One of the sometimes encountered problems with wood siding is blistering and flaking of the finish on the siding. This is caused by excess moisture in the siding. A rain screen wall goes a long ways to head off that problem by venting the moisture laden air out before it can be absorbed by the wood siding.
Building a rain screen wall does present some other construction issues. Such as extra detailing around doors and windows. The extra thickness of the 1x4 furring in the wall requires special window and door treatment to get the siding to sit right and to get the flashing correct.
Plus screening the bottom air entry edge and the upper 'exhaust' air exit is necessary. You don't want to provide a haven for insects to make their home behind the wood siding. There are special insect proof venting materials (Cor-A-Vent) or window insect screening can be used. I do like the Cor-A-Vent; easy to install.
FYI, if the exterior is first sheathed with a reflective foil insulation over the OSB, then furred, that can also increase the effective R-value when the sun is shining on that wall. A 1/2 inch of Polyiso foam (R 3.2 approx. can become become R 5.9 under the right circumstances.
In any event if a rain screen wall is built with vertical furring strips it is a very good idea to use ring shank or spiral nails for their greater pull out resistance. Headlok screws (or equivalent) would be required (by code) if an exterior layer of foam is used.
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razmichael
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# Posted: 3 Sep 2013 08:28am
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Just finished siding my cabin and I did a rain screen. Not a code requirement in my area (but is code in some places - British Columbia I believe). We tar papered the walls, stapled a 24" strip of bug screen material along all the edges (hanging down) then put on the furring strips. I used 3/8 plywood - not a large gap- for the furring strips. This was the minimum suggested thickness and would not meet code in BC (10mm or about .4" ) but I'm not in BC! The reduced thickness also reduced the issues MtnDon mentions with trim. The Cor-a-Vent material MtnDon mentions had to be special ordered here so I used a roll of ridge venting material and cut it into 2" strips. This goes on just below and above the furring strips and the bug net is then folded up over this and the furring strips and stapled down. This provides a bug proof gap where air and moisture can pass. Keep in mind this is also needed above and below windows and doors. Bug screen alone will collapse between the furring strips and is not that effective. The Cor-a-Vent has a built in bug screen. Spiral siding nails on goes the siding.
This method adds a lot of time and effort and half way through the work I was really wondering why I did it (as toyota_mdt_tech states) but it is done! Go a google search on rain screens and you should find some examples (sorry I do not have the links on this laptop). There are some products that you just put up over the whole wall and it acts as your furring strips as well Mortairvent. Cost would add up but install time might be a lot less (than my method).
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grover
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# Posted: 3 Sep 2013 02:16pm
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So it fixes a potential problem and creates others in window and door installation (and extra expense). I was thinking of using the ridge vent material too but it seems it would be too thick. I think its about an inch thick. It might compress enough to work perfectly. I don't see why it wouldn't work to keep bugs out. It does in the ridge vent application.
I had thought of the window and doors issue. I would think 1/2 inch or 3/8 inch treated plywood ripped to 1 1/2 inch strips would work perfectly for the furring strips. I'm assuming you would need to also frame your window and door openings with the same thickness material you use for your furring strips to bring them out to the correct thickness.
Thanks,
Grover
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razmichael
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# Posted: 3 Sep 2013 04:18pm
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The ridge material was slightly too deep for the 3/8 furring strips but I found it was easy to compress - once cut in the strip just lay it on a board and walk up and down on it a few times! Alternative is tap it with a hammer once stapled on the wall. I'm not sure if the bug netting is also needed but I went with it as well to ensure a good block around the corners etc. As you suspect, the framing around windows is not a big deal at 3/8.
Rain Screen
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GomerPile
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# Posted: 3 Sep 2013 04:53pm
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I used the ridge vent material on my build...it compresses pretty well. I have also seen some people use plastic window screen material.
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Canuck Mom
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# Posted: 16 Sep 2013 08:48pm
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I have a fellow finishing my small cabin. He put the timber frames, white painted pine board & batten, then 2 inch foam insulationwith strapping, then plywood, then typar, then this black stuff he is stapling on loosely, looks like chicken wire in 3D, but coated in a black PVC? Then the cedar shakes. Lots of work.
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