Wood for Rainscreen Furring
Well after much researching this weekend and Malcom’s comment on Friday about peoples reticence on commenting on my framed chase details with adhered stone veneer I have come to the conclusion……Yep it was a bad idea. So thank you Malcom for weighing in and getting me to realize the error in my ways! Now on to plan B.
This side of the house and the chimney chase will get Hardie siding and the chimney shoulders will get asphalt shingles, complete with step, base, and kickout flashing and a drip edge. The top of the chase is getting a SS chase cover with a drip edge and diagonal creases. I did end up using the Prosoco joint and seam filler and fast flash on the corners and sheathing joints because I had bought the sausage gun and it was pretty straight forward albeit messy to apply. While I would love to hire a siding company to do the siding most of them will only do a whole house and tell me to just hire a handyman. It’s 200 sq feet so I think we will do it ourselves. No run on this side of the house is longer than 10 feet so I won’t have any butt joints.
The rest of our house has T1-11 siding with a 4″ OC groove. Luckily we have great overhangs on this house so most of it is in good condition. Since this side of the house and the chase will be different than the rest we want something that will look good with the current siding and on the chimney chase. We just tore of old cedar ship lap siding that had been applied diagonally. Options are:
Hardi plank – either a 4″ or 5″ reveal (5/16″ thick)
Hardi Artisan siding (shiplap) with lock joint joint system (5/8″ thick)
We plan to use Hydrogap as our WRB. Both of these products require a drainable housrewrap with a 90% or better drainage efficiency. The lap siding is not flat to wall but the Artisan siding is. Is the Hydrogap enough for my Zone 4c climate? Hardie says it is but I know it’s not a true rain screen. For the commercial application of the Artisan they require a rain screen with specific information on the type of furring:Wood Furring:
If wood furring is not being used as a nailable substrate, there is no wood species or speci c gravity requirement. Furring should be of suf cient width to assure adequate siding fastener connection; widths from 2 in. to 3.5 in. are recommended. Wall corner intersections may require wider furring to accommodate trim.
If wood furring is being used as a nailable substrate, material must be spruce, pine, fir or any other wood species with a specifc gravity of 0.42 or greater in accordance with the American Forest and Paper Association (AFPA) and American Wood Council National Design Speci cation for Wood Construction (NDS).
Wood furring shall conform to building code for natural decay resistance or treated lumber (2012 IBC §718.2). Typical wood rainscreen furring includes treated 1/2 in., 3/4 in., 3/8 in. thick plywood, or treated nominal 1×4 in. lumber (actual 3/4 in. thick).
I can find nothing on compatibility of house wraps with treated lumber. I know Tyvek does like cedar next to it but I saw Hydrogap installed with cedar shingles on it but nothing about PT lumber. Does anyone know?
I know there has been much discussion on this website on whether to use PT or regular plywood for furring. From Hardies tech docs it appears that PT furring is a IBC requirement but maybe it’s only in relation to commercial or multifamily units.
Any comments appreciated!
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