OSB for rainscreen furring?
Hey all – I’m going to be residing my single story house this summer (climate Marine 4c – Seattle). The walls look like this (inside to out):
Gypsum > 2×4 cavity (to be filled with dense-pack cellulose) > 1×8-1×10 shiplap sheathing > 15/30 lb Felt, taped > 1″ polyiso > OSB furring (with core-a-vent sv-5) > hardie plank/cedar shingles.
My main concern is what material to use for furring strips – I realize that 1×4 stock is commonly recommended, but I wanted to go with something a) cheaper, b) more dimensionally stable than 1×4, and c) wider furring than 4.5″, especially in the corners. I had settled on OSB strips due to price, and thickness (because there are shingles and clapboards, I am going to double to furring – all vertical where the clapboards are, vertical and horizontal where the shingles are).
Are there are any concerns with using ripped OSB for furring?
This article merely mentions if you’re using OSB furring to add 0.5lbs to the weight of your siding, and I imagine if there was a great concern with OSB as furring there would be recommendations against it, but I haven’t found any – because the walls will be insulated, there won’t be condensation forming because of heat – but what if the walls are below the dew point?
From what I’ve read, the main concern with modern OSB is that edges swell when wet and this can telegraph through the siding material – should I just paint the ripped edges to “seal” them? Or should I just go with CDX (about 2x as much)? Thanks!
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