durability and splitting resistance of 3/4″ strapping to hang siding over foam sheathing
Has anyone done a post-mortem (or otherwise observed evidence) bearing on the ability of 1 x 4″ strapping to resist splitting due to long-term (several years or more) changes in mosture and temperature while under load? We’re sheathing our Victorian farmhouse with polyiso foam during our renovation, something that is comparatively novel in my part of the world. While my contractor is perfectly open to the procedure, he is skeptical that 1 x 4 strapping made of today’s typical lumber will hold up over the long term once it is under load (we’re hanging fiber cement siding). His theory is that extreme seasonal changes in moisture content and temperature (we live in the Great Lakes, where such swings are typical) will, over time, lead to splitting of the strapping and potential siding failure. Thus he is more comfortable using 2 x 4 strapping. Personally, I’d rather dedicate the extra strapping thickness to more foam (we are limited in total wall thickness by historical trim details) and have read several posts on GBA recommending 1 x lumber for strapping. Any thoughts?
Thanks!
Tony Fleming
Albion, IN
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Replies
I know a lot of people use pressure treated plywood ripped into strips. I personally would feel more comfortable with that over the long term than 1x4. On our jobs we usually use galvanized hat channel, but then we are usually installing cement boards as an open joint rainscreen.
Tony,
I think the 1x4s will hold up fine, as long as they aren't split during installation.
Since these are just spacers, wouldn't the split have to be so large that the firring strips slipped out of place to be a problem? It seems unlikely that they would "fall out", or I think people would have been screaming about problems for decades.