How to Install Fiber Cement Siding
By: Joe Cuhaj
Installing fiber cement siding (FCS)—such as HardiePlank®—is easier than you might think, though there are some important differences from traditional wood siding. Installation instructions may vary depending on the manufacturer, and check with your local building inspector for any code requirements.
Always follow these safety precautions when installing fiber cement siding:
- Wear safety glasses when cutting and nailing FCS.
- Use ear protection when cutting siding with a circular saw.
- Cutting FCS with a circular saw creates a large amount of dust which can lead to the incurable lung disease silicosis. Always cut siding outside and use a dust collecting saw hooked to a shop vac if possible.
- Wear a NIOSH approved N-95 dust mask or respirator when cutting FCS.
Storage and Handling
- Inspect siding carefully for damage when it arrives.
- Store off the ground, making sure it is flat and well supported.
- Keep it dry until it has been installed.
- Carry pieces on edge to prevent breaking.
- Support siding along its length when cutting.
- Sheath walls with plywood, oriented strand board (OSB), or foam.
- Cover sheathing with housewrap or felt paper.
- Pop chalk lines to mark the location of studs.
- Scoring: Fiber cement siding can be scored and snapped like drywall, though the cuts are not very smooth. Score the face of the siding then pull up to break. A carbide tipped scoring knife lasts much longer than a standard utility knife blade.
Fiber cement siding can be nailed by hand or with a pneumatic nailer. It can also be attached using corrosion resistant screws.
- Use hot-dipped galvanized or stainless steel nails.
- Nails should penetrate through the sheathing and at least 1” into studs.
- Position nails ¾” to 1” from the edge of the siding.
- Siding can either be blind nailed at the top or face nailed at the bottom.
- Use roofing nails for blind nailing and siding nails for face nailing.
Begin by installing the inside and outside corners on the wall. These can be made from wood, vinyl, or thicker fiber cement products such as HardieTrim®. Corners should be at least ¼” thicker than two stacked pieces of siding to allow room for caulking.
Fiber cement siding should be installed 6” or more above the grade level of the house with a 1”– 2” gap between horizontal surfaces like decks, steps, or adjacent roofs. Flash above doors and windows, leaving a ¼” gap between the flashing and siding. If you’re working alone, overlap gauges can be used to support the siding while you nail it.
Begin by attaching a 1¼” wide strip of FCS 1/8” above the bottom of the first row to provide the proper angle for the siding. Next, nail the first row of siding into the studs, leaving 1/8” gaps at the corner boards to allow for caulking. Blind nailing is preferable to face nailing, since any nail heads are hidden by the next row of siding. Nails do not need to be predrilled except near the ends.
Center joints over studs unless special metal off stud joiners are used. Joints should be butted loosely together with a 4” wide strip of 30 pound felt positioned behind each one. Make sure the felt overhangs the previous row of siding to keep water from running behind it if the caulking fails.
Each row of siding should overlap by 1¼” or more. A spacer stick with a notch cut the length of the exposed part of the siding makes alignment easy.
Use a square or level to check that the rows line up at corners. When notching the siding around doors and windows, hold it in place and mark each end. To determine the depth of the notch, hook the spacer stick on the previous row of siding and measure from the top of the stick to the window or door unit.
When cutting angles on gables, start by cutting a piece of scrap siding or wood to the proper angle then use it to mark each piece. To measure the top row of siding on horizontal eaves, hook the spacer stick on the previous row and measure up to the eave, then rip the siding to width.
While fiber cement siding should be painted as soon as possible after installation, factory primed FCS can go as long as six months without painting. Make sure it is clean and dry before painting. Caulk joints and ends first with a high quality latex caulking. Prime bare siding and any exposed cuts then topcoat with 100% acrylic latex paint.