Which material would you choose for rainscreen furring?
Antonio Bettencourt
| Posted in Energy Efficiency and Durability on
3/8″ x 1 1/2″ versus 1×4 untreated pine?
The exterior wall is plywood sheathed, wrapped with Tyvek housewrap, a rainscreen gap and horizontal cedar lap siding.
I can see a number of advantages to using the 3/8″ lath:
cost, less than half the price
a thinner section means standard fasteners can be used
a thinner section simplifies trim at windows and doors
Disadvantages:
a thinner rainscreen gap (not a big deal in my opinion)
material may be more likely to split during installation
Are there any compelling reasons to go with the 1×4 over the 3/8″ lath?
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Replies
Building Science Corp would tell you that anything over 1/16" has pretty much exactly the same drainage potential. The additional depth provides additional ventilation potential. Is that necessary? I am not sure. Perhaps there are folks on here with more experience with the long-term durability of each who could tell you. To me, any drainage plane is massive upgrade from typical US residential construction. Unless you are in an particularlly wet location, either seems very reasonable to me.
The 1x4 may provide some additional support (especially if your framing is 24" OC) by slightly reducing the span for the cedar lap siding. It will definitely be less likely to split.
You might price out 1x3 pine as well to see if there is a middle price option. In my area, that is sold in bundles as "furring" for relatively cheap.
I have used rips of 1/2" CDX sheathing and been very happy with it. It has the advantage of using up leftover sheathing cut offs, and the disadvantage of more labor to rip them.
You are correct that 1/2" or less typically means being able to trim out windows as "normal." If you're not using exterior insulation. Check your specific windows and doors. I think many come 1" to the nailing fin, which would be enough to hide the 3/4" furring as well.
https://buildingscience.com/documents/digests/bsd030-rain-control-theory
I used 3/8-in rips of plywood on my home. I have board sheathing, I installed a self-adhered WRB. I replaced my windows and doors at the same time, so I bucked those out using the plywood. Most of the work was completed in 2019/2020. I opened a small section up this summer to replace a heating exhaust vent. Everything looked exactly the way it did when I originally did the work. I half expected to see a bunch of bugs caught in the window screen I installed at the bottom of the siding, there were very few.
I think I would only go 3/4-in if you add continuous insulation, or as Ben mentioned, you need a better nailer to attach the cladding.
Antonio,
Keeping the cavity clear is important both to maintain the capillary break, and the vent/drainage path. 3/8" works as long as the WRB stays flat - which it does when you use a self-adhered WRB - but mechanically attached synthetic ones, or building felt, almost invariably have wrinkles or bulges that may bridge the gap. Because I use stapled WRBs and our lumberyards stock 1/2" plywood rain-screen strips, that's what I prefer.