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?
On Nov 17, 10:03 am, btombs_at_kgsgroup_dot email@example.com (tombsy)
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.
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.
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...
Furring and or 2x members placed for nailers, with insulation cut to fit
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
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.
On Nov 17, 9:03 am, btombs_at_kgsgroup_dot firstname.lastname@example.org (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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