Helpful? 0

The most value-engineered siding furring strips over thick rigid foam... but what width?

Assuming labor is free, I've found that the cheapest furring strips would be 15/32" plywood. It's quite a bit cheaper than 1x4's (less than half the price, close to a third, if ripped to 2.5"), and can be narrower than 3.5" without worrying about splitting like 1x3's or 1x2's would. Also, it just barely meets the 7/16" penetration requirement that James Hardie has.

But how wide should they be? 2.5" seems like a reasonably safe width, but I'm curious if anyone has real-world experience with smaller furring strips, and can comment on how small is too small.

Asked by Nick Welch
Posted Fri, 04/04/2014 - 20:07
Edited Fri, 04/04/2014 - 20:08


4 Answers

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2 1/2 inches sounds OK to me. But I must say that I am surprised that James Hardie is happy with only 7/16" inch penetration of fasteners. If ring-shank nails are an option, I would select them over smooth-shank nails.

Answered by Martin Holladay, GBA Advisor
Posted Sat, 04/05/2014 - 05:02

Helpful? 1

I also use 19/32" for less nail "bounce" and at $17.5 for a 4x8 sheet ripped at 2.5", I get 19 furring strips @ $0.92. That's half the price of locally sourced 1x4" strips at $1.98 per. I do use "used" ring shanks from Habitat's ReStore for next to nothing (sometimes they clear the shelves for 25 cents a pound.

Answered by Paul Kuenn
Posted Sat, 04/05/2014 - 08:21

Helpful? 0

Thanks for the real world experience, Paul.

Martin, the 7/16" number was surprising to me too, but it is your article and you even followed up about it in the comments. :-) In their documentation, the 7/16" number is given for OSB sheathing -- it doesn't say anything about furring strips. The nail is also required to be quite a bit longer and penetrate well past the inside face of the OSB. But you said the rep was confident that that requirement also applied to furring strips, so I am taking that at face value.

I don't live in a very windy place, and I'm surrounded by trees and houses in an urban area, so I feel fine going with the bare minimum requirements for wind resistance.

But I would definitely be using ring shank nails.

Answered by Nick Welch
Posted Mon, 04/07/2014 - 14:22

Helpful? 1

Nick, With Hardiplank it isn't the wind that will cause the problems, it is applying enough pressure at the fasteners to hold the board tight to the one below. I think you risk having gaps with what you propose.

Answered by Malcolm Taylor
Posted Mon, 04/07/2014 - 15:11

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