Best furring strip over exterior foam to hold Hardie siding?
Ok, this has come up before and I want to get final recommendations from those who have done the work in the field as my foam board is almost finished.
I have attached 2.5″ of recycled EPS to the exterior over my drain wrap. Windows are INNIES and are flashed well. As a point of fact, the Tyvek brand tape worked and adheres excellent to the EPS. I have some 3M all weather tape but the Tyvek tape works great and is easier to work with.
Nonetheless I am concerned about the initial recommendations here about 1×4 common pine furring strips. Would not 3/4 or 5/8 OSB cut into true four inch strips work better at holding the nails for the Hardi siding and Miratech trim? I really think the “grip” will be better in OSB and I am concerned that the pine will a. warp and b. split. Or be more likely to.
Thoughts before I move forward. I don’t own the furring yet but have a bunch of OSB material left over that I can repurpose and rip to work.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Joe,
Here in Vermont, most local mills use spruce, not pine, for 1x4s. Either species will work well, however.
I prefer to nail into solid wood, not OSB. Moreover, a rough 1-by will be 1 inch thick; a planed 1-by will be 3/4 inch thick. Either of these beats a 5/8-inch-thick strip of OSB, in my opinion.
Before you use 5/8 inch OSB, make sure that the material is thick enough to meet Hardie's requirements.
Joe,
Evidently (according to an article I wrote a while back but forgot about, Fastening Furring Strips to a Foam-Sheathed Wall) Hardie accepts a nail penetration depth of only 7/16 inch for some types of siding. But I would still check with Hardie before proceeding.
You may also want to read this document: Applying James Hardie Siding over Continuous Insulation and Non-Nailable Substrates.
I was considering mostly 3/4 OSB advantech I had left over from floor. But what you say makes sense. Rough hewn until led 1x4 probably would be best. The advantech might be good for the corners. If I used 3/4" milled furring 1x4.
I will be in similar situation with 2" of Polyiso as my ext. foam, and was planning to use a 5/8 or 3/4 plywood ripped into strips for the furring. The final wall material is either Swisspearl cement board or FbreC öko skin cement board (somewhat heavier than Hardie) in an open rain screen design on one part of the home, and 16 guage steel on other parts, so would the plywood be a suitable furring strip?
Lastly, do the furring strips in this situation need to go into the wall studs, or just the sheathing?
Thank you :-)
How are these dispicable Chinese being delt with? Getting into the forum is extremely difficult.
Joe,
The I.T. team at Taunton Press is coming up with a plan to deal with the Chinese spammers. Until that plan can be implemented, here's what's happening: I have to delete the spam by hand, one at a time. I'm trying to keep up with it, but it's a struggle.
Steve Wilson,
I'm unfamiliar with the siding types you list.
Furring strips definitely need to be fastened to studs, not to sheathing.
Here is a link to an article that gives more information on this issue: Fastening Furring Strips to a Foam-Sheathed Wall.
If you still have questions after reading that article, you should consult an engineer.
Thanks Martin, I will double check with the engineers on the project just to be sure. FYI the products are european cement board cladding systems. Through colored cement board that is more dense than Hardie, and does not require painting. Here are a couple links for yourself and others to explore if desired.
http://www.swisspearl.com/swisspearl/
http://www.rieder.cc/at/en/main/products/
My sider, who I collaborate with really wants to use what he is "comfortable" with which is 1x4 pine rather than the unmilled true 1x4 stock. So the furring strips will be 3/4" x 3.5" and there are a few reasons for that: One is that he has quite a bit of the material from remodeling interior (window and trim replacement jobs) that can be repurposed and Two- we can use 3/4 Advantech floor sheathing for the corners so we can get 10" wide strips tightly fastened allowing for trim and siding attachment. We have several sections and a half dozen full sheets left over from the build, so we get to re use a lot of material that other wise might be collecting dust. The six inch screws work nice getting into the meat of the studs too and with no inside sheetrock or insulation yet, we can double check that we are hitting solid studs everywhere. The screws are going in every two feet. However a local yard will produce true 1x4 rough hewn stock for 18 cents a linear foot. But delivery is more that the 1500 LF of product! So that is where we ended up. Much of the furring and all of the foam is recycled. You should hear the comments. Apparently no one in this area (Saratoga County NY) has put 2.5inches of exterior foam on their house. It is quite an oddity for people. Lots of folks are perplexed about the window trim. My sider has given up trying to explain that there is actual carpentry involved. He just says to them "I am building INNIES" to confuse them more. LOL I will try to post a few pics. The 3M and also the Tyvek tape work to seal the foam joints very nicely and I have several porch rooks that come off the house that need foam up and inside them against the sheathing. It is a nice place to use the scraps which are cut and cobbled together to fill between and over the ledgers and space between the rafter ends up there. In some places I am able to cut, cobble and glue as much as 7,5" of foam against the sheathing using construction adhesive and bit of canned spray foam. At least it is not going to a landfill,
This is an interesting discussion and one I will follow since I'm in the same boat so to speak... I am building Dudley boxes from 3/4 construction grade plywood for my project which has 4" pf EPS foam on the exterior of 2x6 walls (zone 7) and plan on using the same material (3/4 ply) for the furring strips...
please don't let this thread die ... those of you that have done this please chime in and those that are planning on using OSB/plywood/spruce/pine/etc or various thicknesses please do the same
Joe,
Where are you located?
Zone 5 Saratoga County, upstate NY
Is there any concern about the longevity of wood furring strips? Will untreated pine or douglas fir survive just fine, or is it a good idea to treat these with a preservative? We are in the pacific northwest (4 marine), getting ready to install Hardie over 2 inches of poly iso. We have a ready supply of doug fir 1" x 3.5" (actual). I'm debating whether to treat them with a preservative before installing per the Hardie guidelines.
Guy,
I think Mark is right. There is no reason to believe the furring strips will rot.
Guy, I'd love to see your project (seeing as you're in the same climate zone I'm in- PNW).
If wood can dry out it'll last. Others with actual experience can comment more directly, but I would think that you're not going to be getting enough water/moisture on those strips to cause them stress. I have exposed wood decking (old and one of the reasons why I'm looking to scrap everything and build a new house!) and seeing as it's on the south side its been holding up for a good 8 years now without any sealer on it (I quite putting it on 8 years ago- it was likely 10 years old when I bought this place, so figure it's almost 20 years old). I rung up 101" of precip in 2020. This is my actual experience.
I'd think that putting a preservative on the cut ends might mitigate the concerns.
I'll be following this as I have yet to decide on the details here (I'm considering vertical siding, which means having furring strips running horizontally).
Mark,
Remember that the BCBC requires a continuous (uninterrupted) vertical cavity behind cladding, so if you use horizontal furring you either need a second layer underneath, or to use a proprietary product like Cor-a-Vent which allows air-flow and drainage.
Malcolm, yes on the two layers (and I also have Cor-a-Vent in mind- two layers of furring is going to really start pushing things out a bit). I won't really decide until I go over things with an architect: a decent virtual look should help me decide (well, my wallet will have some say in the matter as well!). Full siding height is also going to factor in.