jdebree
Basic Member
Posts:497
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| 18 Feb 2012 05:12 PM |
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This should be easy, but I'm having a hard time answering a basic question. I plan to build my house with 1" (or more) foam over the structural sheathing. I then plan to create a drainage plane using 1X4 wood, screwed through the foam, into the studs.. Over that- fiber cement lap siding. The problem is that I can't find a satisfactory answer as to how to attach the siding. None of the major manufacturers seem to address this, nor do the building codes. The siding manufacturers specify 1-1/4" fastening into solid wood, which is pretty hard to do with a 1X. I plan to use SS ring nails, and figure going through the furring by 1/4" or so should be as good as it's gonna get. Should I go to a 2X4 for furring? That seems like overkill. Funny- I see references to this all the time, but no specifics. In my damp SC climate, I definitely want a drain plane behind the siding, but I don't want to use long enough nails to go through the siding, furring, foam, and into a stud. What's the accepted rule for this?
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Chris Johnson
Advanced Member
Posts:878
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| 18 Feb 2012 06:12 PM |
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On ICF we use 1x fastened to the plastic strips for vertical siding and attach siding without issue. |
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| Chris Johnson - Pro ICF<br>North of 49 |
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jdebree
Basic Member
Posts:497
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| 18 Feb 2012 09:39 PM |
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Attach siding with what? Nails? Screws? What length? I can't tell you how much searching I've done, and found nothing about the specific fastenings. I need to order nails soon, and I don't want to order the wrong kind at $150 a box. |
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ICFHybrid
Veteran Member
Posts:3039
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| 18 Feb 2012 10:08 PM |
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When you look into the technical specifications on the fiber cement siding (Hardie, Certainteed, etc) they all have very specific minimum requirements for fastening. The minimums are necessary to get the fastening and wind resistance you need. Read the instructions for the product you intend to use. Even if they don't address your exact type of construction, you will get a pretty good idea of what is going to work. You can always drop a line to the manufacturer's tech center as well. Stainless is overkill unless you are dealing with treated lumber or have other electrogalvanic issues. Hot dip galvanizing is probably fine for the fasteners and will save a lot of money. Ring shank nails are good if you are going to wood. For some ICF manufacturers, ring shank nails are acceptable, except in cold weather, but screws are preferred. I wouldn't use the nails with ICF on a quality home. |
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jdebree
Basic Member
Posts:497
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| 19 Feb 2012 08:33 AM |
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All of the manufactures call for 1 or 1-1/4" minimum into wood. I guess that means 2X furring. I've seen references all over the web talking about or showing 1X furring. Even the book I got from JLC on energy efficiency talks about it, but no mention is made of the specific fastenings. There's a lot of talk about how to fasten the furring strips, but it ends there. It's been suggested that I also ask the building inspector, which I could do, if I can reach one on the phone. Right now, I'm 600 miles away, trying to fill my nail order before I head back up there to resume work. Right now, I can only assume all of the builders using 1X furring aren't meeting the minimum, but are getting away with it. Unfortunately, the technology is too new to indicate what might happen 20 years down the road. |
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3cityblue
Basic Member
Posts:111
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| 19 Feb 2012 10:15 AM |
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I feel your pain jdebree. I am planning a similar installation but plan on using SIPS so won't even have studs to fasten to, just the OSB. Is the most important connection the furring through the foam and into the structure? Would seem to me if that connection is solid then the manufacturers guidelines for fastening would work at the siding to furring connection. But I'll be darned if I can find anywhere that addresses this issue for regular framing much less SIPS. Have even run across a few places that suggest it can't be done. Whatever the solution I plan to use screws for all attachments. Just need to know spacing, patterns, lengths. Will be interesting to see if the combined experience of this forum has any specific solutions. Good luck with your build. |
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arkie6
Veteran Member
Posts:1453
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| 19 Feb 2012 10:49 AM |
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Another option for a full 1" thickness furring strip is to buy 5/4 x 6 treated deck boards and rip them in half. This gives you a full 1" thick x 2-1/4" wide board. There is more work involved with ripping the boards, but cost wise this is about the same as 1x4 furring strips. The local Lowes shows 1x4x8' furring strips at $1.96 and 5/4 x 6 deck boards at $4.20. Plus the deck boards are treated and you should never have to worry about rot or termites. Just make sure you are using corrosion resistant fasteners. |
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ICFHybrid
Veteran Member
Posts:3039
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| 20 Feb 2012 01:36 AM |
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All of the manufactures call for 1 or 1-1/4" minimum into wood. When you are using the proper nails, Hardie allows for minimum 3/4" penetration into a structural member, like furring. However, if you are shooting for that minimum, I would look very carefully at the lumber being chosen for that furring as well as consider your particular wind resistance needs. |
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Alton
Veteran Member
Posts:2164
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| 20 Feb 2012 12:22 PM |
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I wonder if composite decking material for furring would be better to use than treated wood? I know the composite decking that I have used appears to hold screws better than wood. Of course, the cost for composite decking at Lowes and Home Depot would cost more than treated wood but there should be no culls or later problems with twisting, warping, etc. My only concern would be if the composite would expand more so than the fiber cement could tolerate. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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jdebree
Basic Member
Posts:497
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| 20 Feb 2012 04:58 PM |
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In doing further research, I have found a few references that say it 'should be adequate', meaning 1X furring. That's a little vague.
I do have a few factors which lead me to believe I'll be OK. I'm in a low wind area, plus the house is in a heavily wooded area. On windy days, there's barely any wind at all down at ground level- all the wind is up in the tree tops. I'm also going to be framing and fastening on 16" centers, rather than the maximum 24". My siding is Nichiha, which I bought at close-out for 1/4 retail price. I'm not too worried about the warrantee so much as I am about the inspector red-flagging my installation. I will try to get their OK before I proceed. |
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johanson
New Member
Posts:12
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| 21 Feb 2012 04:57 AM |
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I have completed several projects that use foil-faced polyiso as the exterior rigid insulation board. I install 1x furring strips vertically over the foam to support fiber cement lap siding. The furring strips are attached to the studs with 4" screws at 6" to 8" o.c. I do not use the foam as the drainage plane however. The foam is installed over a continuous rubber membrane which is installed over a 1/2" CDX plywood sheathing.
As mentioned the air space increases the r-value slightly, the foil facing gives me a radiant barrier (a benefit here in Austin) and a ventilated siding will maintain it's finish over time better than an unventilated siding.
Good luck with the project.
Is the rubber membrane a vapor barrier? I would assume that it is. Are you insulating the stud bays with fiberglass? I suppose in your climate it is better to have the vapor barrier on the outside because of the summer cooling loads. |
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| <a href="http://www.eastcorkcranehire.ie/">Crane Hire</a> |
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jdebree
Basic Member
Posts:497
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| 21 Feb 2012 06:16 AM |
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Thanks, Johanson. What fastenings do you use to attach the siding to the furring?
I plan on using Zip sheathing with taped seams for a barrier. The stud bays will probably be cellulose. From what I've read, you only need screws every 24" in the furring strips, but that doesn't seem like nearly enough. |
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Bob I
Veteran Member
Posts:1435
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| 21 Feb 2012 12:03 PM |
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I've used 1x3 strapping over 2" XPS foam - strapping is screwed into the studs with GRK screws or similar. Then the FC siding is nailed with roofing gun into the strapping. Have had no problems. I do use plywood rips around the windows in place of the 1x3; better fastening surface for the windows. |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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greentree
Advanced Member
Posts:587
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| 21 Feb 2012 08:40 PM |
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Bob,
What length roofing nails are you using? I'm assuming you've had no issues with that?
We use the hitachi siding nailer for fiber and lp smart and the fastener cost is ridiculous. |
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rather be fishing
New Member
Posts:1
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| 24 Feb 2012 09:55 AM |
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I have a similar job in which I have 1” foam straight the 2 x 6. No OSB in-between. I am planning on replacing the cedar siding with FC. I was thinking Tyvek over the foam then using 3” ring hot dipped siding nails with ½ OSB firring strips. (should I use someting else) Using the firring strip so not to crush the foam using a nail gun. What do you guys think? Is there concerns with this approach. |
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DickRussell
Basic Member
Posts:182
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| 24 Feb 2012 11:08 AM |
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For interest, there is an article in the new (February 2012) issue of the Journal of Light Construction (page 61), "Securing Rainscreen Siding." For the article, the authors built test assemblies involving 3/4" strapping over 2" and 4" of foam over sheathing, with HeadLok screws through all of that. It presents the test results for vertically stressing the assemblies to destruction. Finally, page 64 gives a fastener schedule for different types of siding, insulation thickness, and stud spacing. Nothing like a good table based on hard data. |
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Dana1
Senior Member
Posts:6991
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| 24 Feb 2012 11:29 AM |
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Posted By rather be fishing on 24 Feb 2012 09:55 AM
I have a similar job in which I have 1” foam straight the 2 x 6. No OSB in-between. I am planning on replacing the cedar siding with FC. I was thinking Tyvek over the foam then using 3” ring hot dipped siding nails with ½ OSB firring strips. (should I use someting else) Using the firring strip so not to crush the foam using a nail gun. What do you guys think? Is there concerns with this approach.
I hope you've cut in some bracing to keep the wall from racking(?). Ripped down half-inch OSB isn't nearly as rigid as 1x or 2x timber, and will require more fasteners(==more thermal bridging) to get it to lie flat and be mechanically strong enough. It's better to use at a minimum 1x4 furring (1x3s are more likely to split and aren't as rigid) screwed to the studs with 24" o.c. fastener spacing, and install the fiber cement with fasteners that don't go any deeper than the furring. Steel is more than an order of magnitude more thermally conductive than wood, and more than 2 orders of magnitude more conductive than foam, so keeping the number of penetrating fasteners low is key to getting the full performance out of your foam. |
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jdebree
Basic Member
Posts:497
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| 24 Feb 2012 04:10 PM |
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Posted By DickRussell on 24 Feb 2012 11:08 AM
For interest, there is an article in the new (February 2012) issue of the Journal of Light Construction (page 61), "Securing Rainscreen Siding." For the article, the authors built test assemblies involving 3/4" strapping over 2" and 4" of foam over sheathing, with HeadLok screws through all of that. It presents the test results for vertically stressing the assemblies to destruction. Finally, page 64 gives a fastener schedule for different types of siding, insulation thickness, and stud spacing. Nothing like a good table based on hard data.
That's a great article, but, believe it or not, they never mention how to fasten the siding to the furring strips! They also point out that the testing in no way means the fastening is adequate for wind or seismic loads. I'm going to go with ring siding nails, and call it good. I doubt the inspector will object, although I am going to ask before I do the actual installation. The manufacturer of the screws calls for at least twice as many fasteners as the article does. Seriously, I doubt a few extra screws would make a measurable difference in heat transfer, unless you're building a house in a test lab. I'd rather have more screws on a stormy night than save a couple dollars cents a year in heating costs. |
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Bob I
Veteran Member
Posts:1435
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| 24 Feb 2012 04:32 PM |
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we use standard length roofing nails - probably 1-1/4", which have worked fine. No reason to use nails longer than needed to go thru the siding & into/ thru the strapping. |
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| Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant |
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rimce44
New Member
Posts:3
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| 26 Feb 2012 08:08 AM |
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Find some good ideas, thanks |
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