# Hardie Lap Siding over Furring Strips



## e247 (Dec 18, 2017)

I'm working on the details for the siding (HardiePlank) installation on my house and I have a few questions on what nails to use. 

The walls are 2x6 wood studs, 16" O.C. with 5/8" OSB sheathing. There will be 3/4" rigid foam installed over the OSB with Tyvek over the foam as the WRB. I planned to run 1 x 4 furring strips over the foam to make a rainscreen but I had a question on what nails to use to attach the siding to the furring strips. I looked at the Best Practice Guide for Hardie Plank installation in HZ10 and it says:

_"When attaching lap siding products over wood furring, the typical fastener used is the 1-1/4 in. long No. 11 galvanized roofing nail, blind nailed. This fastener is going to be the shortest fastener approved for fastening lap siding products, therefore the furring must be a minimum of 0.75 in. thick..."_

But, a few paragraphs above this statement, it says _"the fastener chosen must be fully encompassed by the wood substrate"_ when attaching siding to wood furring and the picture shown in the guide shows the nail does not exit the furring strip. 

So, if the nail is 1-1/4" long and the furring strip is 3/4" thick, the nail will actually exit the back of the furring strip and not be "fully encompassed by the wood substrate". 

To me, it sounds like the guide gives conflicting advice on what nails to use. Does anyone have advice on what nails would work best for my application? Should I use 2x4 furring strips instead of 1x4s so that the nails are "fully encompassed"?


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## Gregsoldtruck79 (Dec 21, 2017)

While estimating the Hardieboard to be a thickness of .375 in. (?) and the wood fir strip to be .750 in. thick. 

.375 + .750 = 1.125. So to me, a one inch long nail will stop .125 or 1/8" short of going out the back of the 3/4" fir strip when nailing the HB on to it. 

https://www.lowes.com/pd/Fas-n-Tite-5-lb-11-Gauge-1-in-Galvanized-Steel-Roofing-Nails/999996386


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## e247 (Dec 18, 2017)

The minimum nail length according the instructions is 1-1/4", not 1". The Hardie Planks are 5/16 thick (0.3125) so the thickness of the Hardie and furring strip is 1-1/16". A 1-1/4" nail will stick past 3/16".


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## Gregsoldtruck79 (Dec 21, 2017)

Are these 2"x"6 inch exterior walls going to be fully insulated and have all air leaks sealed ? If so, you are really complicated matters on your HB installations by adding 3/4 " thick rigid foam panels on the exterior, to what I think will already be a WELL insulated home. IMO. 

How many decades do you have figured for payback from energy savings, by adding this much work and materials costs from a 3/4" foam board wrap ? 

I think once the HB is installed on the 3/4 " fir strips that is nailed over 3/4" foam boards, one will be able to look down along side of a long wall of HB, and it will look like it was nailed on an alligators back.  JMO though


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## e247 (Dec 18, 2017)

Thanks for the feedback Gregsoldtruck79. The exterior rigid foam is to reduce the thermal bridging of the studs providing a better wall insulation system and the furring strips are to create a rainscreen that allows ventilation behind the siding. The furring strips will be screwed to the studs and care will be taken to keep the furring strips on the same plain so that the siding isn't wavy.


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## joecaption (Nov 30, 2011)

I'm with Gregsoldtruck79 on this one.
Understand the concept, but just not worth the added expense and time. 
Never once have I seen anyone on the east coast adding a rain shield.
The House wrap takes care of that.
Add that foam at about $40.00 a sheet and your going to have to now build out every window and door opening.


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## Nealtw (Jun 22, 2017)

Out here everything but vinyl siding requires Rainscreening.
I expect Hardie to suggest a full 1" strapping. with out the foam we use treated 1/2" plywood strips and that should be doubled up.


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## Gregsoldtruck79 (Dec 21, 2017)

I just spent some serious browsing time on the topic here. I now must apologize to the OP, for I now realize that I did not know anything about his subject matter of "rain screens". 

Now that I do know why "rain screens" are now required in various geographical locations behind HB applications, I will just state my newly formed opinion. 

Where I retired from during the $10 million renovation, HB horizontal plank siding was used. On many areas of the buildings it was not feasible to continue the brick from the ground up on the 20K sq.ft. sometimes VERY tall additions. So the architect specified HB horizontal planks lapped, installed over 1/2 CDX plywood Tyvek wrapped only, on the exterior wall 2" x 6" studs. 

For the 11 years after the install and the day I left, the HB planks and paint on it were just as good as the first year the work was done. The only problems I had to deal with was where any flashing had been done incorrectly, which allowed direct penetration of water behind the HB. 

While knowing these "rain screen" installations not only have the added materials cost and labor just for the screen itself, it does not stop then. The complexity of exterior wall penetrations being done through the rain screen post install (HVAC lines, electrical, furnace vent pipes, etc), the needed "extensions" of all door/window jambs inside, the cost/labor for paint, (exterior paint is a lifetime of maintenance) and to me, having basically the "open" channels behind the homes HB for insects and maybe even rodents to enter just so the HB can "breathe" on and on.....

So IMO, if I was building a home that was under the rain screen requirements for my exterior wall cover....I would not be using HB as my exterior wall cover. Millions upon millions of homes today have vinyl siding and even the "upper class" homes use a combo of brick and vinyl siding. JMO


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## Nealtw (Jun 22, 2017)

Gregsoldtruck79 said:


> I just spent some serious browsing time on the topic here. I now must apologize to the OP, for I now realize that I did not know anything about his subject matter of "rain screens".
> 
> Now that I do know why "rain screens" are now required in various geographical locations behind HB applications, I will just state my newly formed opinion.
> 
> ...


 You have missed a few points. Most of the idea has been found on some Victorian houses and has been adopted because it works. Brick veneer has been installed with a drain plain for as long as I remember. 
Doors and windows get installed as before and a bug screen is added at the bottom.


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## e247 (Dec 18, 2017)

Thanks for the suggestion Nealtw. We are in a hurricane zone and we have to design for 120 mph winds. Is the 2 layers of 1/2 plywood strong enough for this application?


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## Nealtw (Jun 22, 2017)

e247 said:


> Thanks for the suggestion Nealtw. We are in a hurricane zone and we have to design for 120 mph winds. Is the 2 layers of 1/2 plywood strong enough for this application?


 I would ask Hardiy


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## e247 (Dec 18, 2017)

I've submitted a request to Hardie, but I was hoping to get some answers from people here as well who've done a similar installation.


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## Nealtw (Jun 22, 2017)

e247 said:


> I've submitted a request to Hardie, but I was hoping to get some answers from people here as well who've done a similar installation.


I don't know for sure so I am reluctant to give you a guess, it is to important for that.


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## Gregsoldtruck79 (Dec 21, 2017)

Nealtw said:


> You have missed a few points. Most of the idea has been found on some Victorian houses and has been adopted because it works. Brick veneer has been installed with a drain plain for as long as I remember.
> Doors and windows get installed as before and a bug screen is added at the bottom.
> https://www.youtube.com/watch?v=zuGXgRzWQmM


And you missed one of mine also, Neal.  

I try to only testify as to what I have seen or experienced in my life here in my state. I stated above the $10 million building/property that I maintained had NO negative effects from not using a "rain screen" for the HB planks used on it. And now 14 years later, I can drive by it and it still does not have any notable. So to me, these "rain screen" requirements depends on the geographical location of where the HB is being used. 

My bias against any painted exterior coverings just come out impulsively I guess. People do not realize what a lifetime of maintenance SO MUCH painted wood on the exterior of their home will mean in labor and $$$$ spent as the years pass by. (note the constant rise of quality paint prices) 

Being a senior now and on a fixed income, I cannot imagine having to pay someone to maintain the exterior painted wood on our home. (which to my choosing, thankfully I have none to paint ) JMO


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## Nealtw (Jun 22, 2017)

Gregsoldtruck79 said:


> And you missed one of mine also, Neal.
> 
> I try to only testify as to what I have seen or experienced in my life here in my state. I stated above the $10 million building/property that I maintained had NO negative effects from not using a "rain screen" for the HB planks used on it. And now 14 years later, I can drive by it and it still does not have any notable. So to me, these "rain screen" requirements depends on the geographical location of where the HB is being used.
> 
> ...


 I think you are right about it being more important in a wetter area. Rainscreening was adopted here after we had a problem with leaky condos where hundreds of building had to stripped down and resided, they had all kinds of siding installed in what ever plan some architect came up with.
https://en.wikipedia.org/wiki/Leaky_condo_crisis
I we accept that paint and caulk will fail over time and wood will rot and windows will leak at some point we now deal with the water that will get past all that. Houses of age like early 1900s were built with wood siding that did well with out constant painting because they could dry to both inside and out. Insulation and vapour barrier interfere with that process so this an upgrade that will best deal with the problems.
People with Victorian houses with wood siding in very good shape often complain about insects entering this gap because they are missing the bug screen that is now used and can be added to those old beauties.


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## Nealtw (Jun 22, 2017)

e247 said:


> I've submitted a request to Hardie, but I was hoping to get some answers from people here as well who've done a similar installation.


 We could hardly complain about hurricane winds here but we do see the odd piece lost to wind. The explanation I have had from installers are either the nails are in the wrong place or the boards should have been narrower as the wider ones were susceptible to the wind.


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## e247 (Dec 18, 2017)

Here is the response from Hardie tech support:

_When attaching lap siding products over wood furring, the typical fastener used is the 1-1/4 in. long No. 11 ga. roofing nail, blind nailed. This fastener is going to be the shortest fastener approved for fastening lap siding products, therefore the furring must be a minimum of 0.75 in. thick to achieve the same values as ESR 2290_

So, basically gave me the answer from the best practice guide and made no comment on the nail exiting the furring strip. I asked about using a siding nail and they told me that I would need to use a 2x4 for the furring strip in order to use the recommended siding nail; which seems like overkill to me. 

Does anyone have advice on using 1x4 board vs ripping down 3/4" plywood for the furring strips? Which is a stronger? I planned on using a ring shank roofing nail.


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## Nealtw (Jun 22, 2017)

I see we have a local company that supplies 2" strips of 3/4 plywood, you may want to do a search in your area.


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## Marson (Jan 26, 2018)

To the previous posters, adding an inch of foam is a common practice in cold climates. A 2x6 wall is NOT considered a "well insulated" wall but is code minimum. There are different conditions in different parts of the country. 

A rain screen is also a good idea. Just like stickers are used to dry lumber, the rain screen allows the siding to dry front and back, and actually would prevent the Hardie from buckling.

To the OP, I think either plywood or pine would be fine for furring strips. Question would be cost, how you feel about ripping all that plywood, etc. Plywood won't split when it's nailed which is nice.

This being an internet forum, my unasked for advice is to consider using lath for furring and nailing through the lath and the foam and into the framing. I have done this, though with cedar siding. Not sure if it is kosher with FC or not.


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## e247 (Dec 18, 2017)

I asked Hardie about using strips of 3/4 plywood instead of 1x4 for the furring strips and they said that plywood cannot be used since it doesn't have the same holding power as wood furring.

I considered nailing through the furring strip and foam into the framing, but that will require a fairly long nail (~3.5"). Also, I would be worried that the nail could compress the foam insulation in some areas making the siding look wavy.


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