Fiber Cement Siding - Installation

I laugh when I remember the first time I used Hardiplank. It arrived soaking wet. Reaching down to pick up the first piece, it snapped in two, and I learned my first lesson. Handle Hardiplank on its edge, even when it is dry. Not only will it break when it's wet, if you install it in this state, it will shrink as it dries and cause problems. Do not hesitate to demand that it arrive dry.


Cutting Hardiplank is the most unpleasant part of the whole installation process to me. Although it can be cut smoothly and accurately, it definitely does not cut like wood. It is best cut with a circular saw with carbide tip blades.


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Unfortunately, this material eats blades alive. For example, if you cut fiber cement all day you will need 2 or 3 blades a day to maintain a high quality cut.

In addition, cutting fiber cement is very dusty. Protect your lungs with a respirator. (A warning is printed on each Hardiplank bundle: "Caution: This product contains silica, which has been known to cause lung damage; use proper respiratory protection." Also wear ear plugs. My little brother is the sawman for our outfit. He found a lightweight dust mask called Dustfoe 66 at Highland Hardware in Atlanta which works well.
The instructions say you can cut Hardiplank with a special knife, but we found it did not work very well. The knife scribes a line, then the siding is snapped, similar to how Plexiglas is cut. The edge is not as clean nor as smooth as a saw cut.

Also, I must warn you that cutting Hardiplank is very hard on saws. A saw used on Hardiplank won't be much good at fine cutting wood after a house or two. The lumberyard believes the dust gets into the saws and wears down the bearings. We have a saw that is used only for Hardiplank and it is never used to cut wood. Keep this in mind when pricing a fiber cement job.

Nailing Hardiplank is similar to nailing other sidings-it can be either blind nailed or bottom nailed. We prefer blind nailing everywhere possible, and since we are old fashioned, we use hammers. I know some will disagree, but this product looks best when hand-nailed. I have found power nailers to either overnail or undernail, especially over foam sheathings. If overdriven, the nails will compress the underlying foam sheathing, giving the siding a wavy look. Foam sheathing is desirable from an energy standpoint, but harder surfaces such as plywood and oriented-strand board (OSB) are much easier to nail into and make for a better looking job.

One way to get the best of both worlds is to use foam sheathing and then nail a 2-1/2-inch plywood strip nailer on each stud. This is called a vented rain screen. Not only will this give you a better, stiffer surface to nail to, but it will ensure long-term protection of the materials behind the siding. If water does get behind the siding it can drain away or dry out in the gap created. If you are using wood sheathing, most manufacturers recommend using building paper under the siding and corner boards to prohibit wood rot.

To blind nail we use 3-inch roofing nails. The large heads of the nail help force the siding flat against the wall and close most gaps where the siding laps the preceding piece. Before handing up a piece, my brother would scribe a line with a combination square 1-1/2 inches from the top, which shows just how far down to nail. The lower down you nail the fewer gaps you will have. You can also use the line as a guide for the next piece, although its a good idea to chalk a line about every 3 runs or so to keep things straight.

You only need pilot holes at the ends. Drill pilot holes a little smaller than the nail shank to protect the corner. We also pre-drill a hole when we are forced to bottom nail. When a nail is driven through an undrilled place, the nail will bust out the backside, like a shotgun blast, blowing out so much material that the nail really doesn't have a lot to hold to. It won't take much to pull the piece loose. Pre-drilling prevents this problem. Yeah, it takes a little longer to do it this way, but you won't have to fool with loose siding and unsightly holes later on.

When we nail on the bottom, we use number 10 galvanized screws or ringshank nails. Don't overdrive them past the surface- aim for flush or maybe a tad proud of the surface. To keep from having to nail at the ends at some boards, you can use what is called preformed metal joints. Use them when the siding breaks between the studs. They do increase the speed of the job somewhat, but I really don't like the look, nor the fact that the joints are not as stable, which makes caulking difficult. In this case, putting Hardiplank over foam does make working the joints a little easier when you don't have to worry about compressing the foam at the joints.

Jim Buchta, "Fiber-cement siding products gain popularity",   


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