Hardie Board over foam board


I have 1 1/2" foam insulation installed on my house. We would like to install Hardie Board over that, but the Hardie website states that it can only be installed over 1" foam insualtion.
Can I still get away with it if I use longer nails or screws? Anything else I should know about?
Thanks -------------------------------------
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On Nov 17, 10:03 am, btombs_at_kgsgroup_dot snipped-for-privacy@foo.com (tombsy) wrote:

You should call Hardie tech support and ask why they have the restriction. 1.5" foam isn't much more likely to crush than 1" foam, so I'd think that it has to do with the weight of the fiber cement siding. Maybe the siding sags over time as the actual point of attachment is further away - the foam wouldn't support the nail by itself and you can't nail it tighter to hold it more securely.
R
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tombsy had written this in response to http://www.thestuccocompany.com/construction/Re-Hardie-Board-over-foam-board-18271-.htm : I contacted James Hardie and they said it was ok as long as I install a Forene Strip or sheathing. Never heard of a Forene Strip (probably not spelled right). Has anyone heard of this?
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On Nov 17, 11:15 am, btombs_at_kgsgroup_dot snipped-for-privacy@foo.com (tombsy) wrote:

I think they probably said furring strip. Google it. That would address the sagging situation.
R
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(tombsy) wrote:

What country are you in?
In the UK we would use battens to stop the foam being compressed.
Furing strips in the UK are normally tapered (eg as used to form a 1:40 slope on a flat roof) but I see in the USA Furing strips = battens.
http://en.wikipedia.org/wiki/Furring
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On Nov 17, 3:00 pm, "Cwatters"

I'm in NY. That Wiki article had the UK usage of firring strips for the tapered roof battens. I think there is a lot of phonetic spelling in construction. Many times I have to pause and translate to determine what a person meant from something they heard from something that person heard from...
R
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(tombsy) wrote:

You should call Hardie tech support and ask why they have the restriction. R
Thank you req
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On Fri, 20 Nov 2009 17:48:34 -0500, "reqluq"

You need to know how to respond to posts in a Usenet group. You need to know how to use quoted text properly. You need to learn how to only add useful information.
<plonk>
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(tombsy)

Don't blame me if the commas didn't go in like they normally do. req
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You need to know how to begin a sentence without "You need to know how to".
(__ Nehmo __)
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On Mon, 23 Nov 2009 09:52:44 -0800 (PST), Nehmo Sergheyev

Oh, we're all so needy... <g>
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Furring and or 2x members placed for nailers, with insulation cut to fit inbetween...... I built an indoor swimming pool with the framing and plywood showing inside the finished room. We reversed the 4x8 sheets of rough saw 4" o.c. lined ply, and put the faqce toward the interior of the pool room. The framing was done with a "finish look" in mind, and not rough framing....... On the exterior, we put sleepers on 16" layouts, and put insulation inbetween. On that we installed hardi board......... Wiring was routed out through the insulation and wire protected at nailing areas. Foam was used to fill any gaps......It worked well..... We did this on the ceiling also. Yes it was difficult, and yes it took time, but the finished product is what the owner was looking for. jloomis

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On Nov 17, 9:03 am, btombs_at_kgsgroup_dot snipped-for-privacy@foo.com (tombsy) wrote:

I put 2" of R7.2" foamboard on an exterior then Osb, tyvek and Cedar shingles. I would not from what little I know put any siding directly on foam. It will compress unevenly as your fasteners cant all be secured equaly, then your finish siding will be wavy viewed from a bistance as it bows in and out. Cover it with osb, tyvek, then siding. To do furring strips how can you get them perfectly even, you cant go over the foam because you cant fasten each one without bowing it in at areas, you would have to cut out the foam and insert the furring to the solid structure, then its not cheap furring, its an expensive 2 x since dimension is less. It was alot bigger job then I expected and payoff was less than expected due to 100 yr old design. Hardi board, isnt that heavy concrete board? You should reconsider a lighter material as I dont know how Osb will react to all that weight, I used the thinnest Osb, but Hardiboard and its weight could over many years ruin the thin stuff, and you will need alot more fasteners on the Osb to hold hardiboard. Overall the job is a headache and you are experimenting with something that wont last if your choises are incorrect. Have you also considered insulation on the exterior in extremely cold zones like Zone 5 allows winters condensation to possibly form on the foam touching the exterior, and your house non breathable. With new windows and foamed walls and a condensing heat system you will need a heat recovery fresh air system, or leave a window a bit open all winter. The head aches of converting old houses to be efficient can be agravating.
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