Info for Insulating and Hardiplank Install


Old 10-24-07, 04:20 PM
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Question Info for Insulating and Hardiplank Install

Hello All,

New to the forum, and while I did search to see if these topics might have been covered, I didn't see the specific questions asked so...

I'm planning on replacing wood siding with cement fiber on my house which is in MA. The old house has little to no insulation at the moment and while I have the siding off and the sheating visible I've thought of adding Dow TUFF-R foam panel insulation over the sheating before wraping and adding the cement fiber boards.

While I was researching the project at a local lumber yard I was told I might not want to put the insulation up as the softness of the panels, which when it has a nail put in could cause divets (for the lack of a better word) in the surface of the insulation could result in a an uneven surface for the Hardiplank. I would think that the cement fiber is rigid enough not to bend like wood might, but I could be wrong.. If anyone could comment on this I'd be grateful. I really would like to add insulation, but not if its going to interfere with the siding install.

While I'm posting, with the cement fiber install in mind any suggestions for a good roofing nail gun or perhaps a siding nail gun for use with the Hardiplank? If I don't use insulation I'm looking at 1 and 1/4 inch nails. If I do go with insulation then more like 2 1/4 or more.

Any thoughts are greatly appreciated!

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Old 10-24-07, 07:06 PM
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Here's a few random thoughts:

>>The old house has little to no insulation at the moment

If that's true, you can also drill holes and blow cellulose into the stud cavities once you have removed the old siding.

>>the insulation could result in a an uneven surface for the Hardiplank.

This is true, to some extent. Fiber cement is NOT a highly rigid product. It's about 5/16" thick, and will follow whatever substrate it is nailed to. Regardless of whether you install foam or not, your hardiplank will only be as straight as your wall is. If your wall has a dip in it, so will the siding.

So let's say you add insulation. The insulation will also follow the contour of the existing sheathing. But it will be rigid enough to span some minor dips... or you can shim out any imperfections PRIOR to insulating, so it actually can help in "some" cases.

Your question, though, was directed more to the "dimples" created when the siding is nailed. Personally, I have never noticed a problem with this. The only time it would happen is if the foam has been crushed, or if there is a void (gaps) between sheets of foam. The sheets of foam (especially Tuff-r) are weakest near the edge of the sheet where the foil facing ends, so if it was going to crush, it would crush there. It could also happen if you hammer a nail in by hand and actually drive the siding in with the face of the hammer as you finish driving the nail. If you're using an air nailer, it should not be a problem. The nail goes in so quickly and effortlessly that there really is not much comression at all, provided you aren't leaning on the gun with all your weight as you nail! If I recall, Dow Styrofoam and Dow Tuff-R have the same compressive strength- 25 lbs per sq in, if I'm remembering correctly. So while you can dent it with your elbow, fingers, or hammer, when you lay something flat on it and nail it, the even distribution of pressure won't crush it. Especially if you're nailing in the right spot- 25 mm (1") from the top of the siding.

I use James Hardie's plastic collated 2 3/8" galv. ring shank nails. They are long enough to work even if you go through 1" of foam. I like the Hitachi NV65AH. You could also look at the Senco SCN56 or the Bostich N66C. I believe that all these guns come with a no-mar tip.

I have on occasion used a roofing gun to blind nail, when nailing directly to solid wood sheathing. But while you can face nail with a SIDING GUN, you should not face nail with a ROOFING GUN.

The large head on a roofing gun will tend to push the siding back very tight. Siding nails, such as those used in the siding guns mentioned above, have small heads by comparison. Siding guns also have a depth of drive setting, which is very important. You do not want to drive the nail beyond the surface of the siding, you just want the nail head to be snug.
Old 10-25-07, 01:53 PM
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Thanks for the info.. I'm leaning towards putting up the foam panels.. The blow in stuff doesn't appeal to me and since I'm probably going to be ripping the interior walls down sooner or later I'd rather not have to deal with that.

Thanks for the nail gun info. I'm probably go with the Bostitch, while I'm at it, any suggestions for a good either shear or blade (any cutting options at all) for the cement fiber? I'm more concerned about good cuts rather than dust. I can deal with dust.

Thanks again!

Old 10-25-07, 03:40 PM
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The fiber cement shears work well, there's a million kinds... they're kinda slow and take some getting used to. You usually use a speed square as a guide as you cut... one the cut is done, I like to smooth the cut ends with a large rasp and then brush on some primer as added protection.

You can also use a skilsaw with the hardie blade, a 4 tooth carbide that is made specifically for cutting fiber cement. It is dusty, and just like drywall dust, it's not good to breath it repeatedly.

Hitachi makes a skilsaw with a dust port that you can hook up to a shop-vac, which is a nice setup to have if you're in the business, but probably not the sort of thing a DIY'er needs.

A 4 1/2" grinder and a diamond blade for cement cutting will also be handy. Sometimes you need to make an exact notch, or grind a bevel, and the grinder is good for that.
Old 10-26-07, 08:46 PM
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XSleeper mentioned the Hitachi nail gun.

Have several brands of nail guns. (Porter Cable, Bostich) Just used my new Hitachi framing nailer today. Had to buy it because my Porter Cable framing gun doesn't fire upside down about 60% of the time and when nailing wood close to the ground, got too frustrated to deal with it anymore.

VERY impressed with the Hitachi.

More expensive but well worth the price for the following reasons.

The tip spring isn't too firm.

Easy controls for triggerless use.

Lighter and better balanced.

Flat surface that allows you to rest the gun upside down and nail straight. (Great for framing on the ground)

Almost non existent kickback.

Virtually no shock to the hands.

Just make sure you use nails with plastic rather than paper separators and if you buy without case, get an adapter "large size threaded male end to connect for air hose). Got home, ready to use, but no way to connect.
Old 11-02-07, 06:00 PM
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I did this project last year. i stripped the siding and sheathing off reinsulated the walls w/ batts. installed new sheathing and wrapped the outside w/ TYVEX and installed the new siding.
I would definitly recommend the HArdi blades. i was using reg. framing saw blades and it wasn't working out that great. The Hardi blades are not cheap but they do last for a while. there are cheaper versions but they do not last as long.
i also used a pnuematic nailer also, I used a SENCO framing nailer with a 2 1/4 " ring shank galvanized nail. It took a lil bit of trial and error to get my pressures regulated to prevent the nailhead from breaking the siding.
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