What Is Hardboard Siding?

Hardboard siding is an affordable yet controversial option.
Hardboard siding is an affordable yet controversial option. (Image: Yellow Wall image by steverts from Fotolia.com)

Hardboard siding is a wood-based cladding product that provides builders a low-cost alternative to wood and concrete siding. However, a series of class-action lawsuits in the '90s greatly diminished its popularity. Chris Hilton, a North Carolina-based building inspector and former contractor with more than 30 years in construction, calls hardboard siding "sawdust, paper and glue," but adds that "properly maintained siding is a good product which will perform well over the long term."

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Hardwood siding manufacturers pass a heated mixture of wood fiber and wax resins through a press to create the sheets that compose hardboard fiber. They then add a layer of embossed paper to simulate the look of wood. Siding manufacturers make three types of siding: lap siding, applied horizontally with each board overlapping the board below it; square edge panels, intended for vertical applications in full sheets; and shiplap edge panel siding, intended for vertical application with the long edge incorporating shiplap joints


Install lap siding over sheathing, using 10d nails, or directly to studs, using 8d nails, spaced no more than 16 inches on center (o.c.). Nail a 1 1/2 inch-wide starter strip flush with the bottom edge of the sill plate. Nail the bottom edge of the first course through the starter strip and into the sill. Lap the second and each succeeding course over the previous course at least 1 inch. Install shim strips behind the siding wherever it is notched above or below an opening. Leave a minimum 3/16 inch minimum space between the siding and windows, door frames and corner boards. Caulk these openings with exterior caulk.

Nail square edge siding to sheathing or studs, using 8d and 6d nails, respectively. Place all siding edges over studs, and nail at least 3/8 inch from the edge and into the stud. Nail shiplap edge paneling to sheathing or studs a maximum of 24 inches o.c. Leave at least 3/16 inch between both square edge and shiplap edge panels and windows, door frames and corner boards. Caulk with exterior caulk.

Allow at least 6 inches between the ground and siding.

Cut siding face up with hand saws and face down with circular saws. Use corrosion-resistant nails and penetrate at least 1 1/2 inches into the stud.

Caulk nail holes and paint installed siding with high-quality, oil-based exterior paint


Inspect hardboard siding yearly. Keep siding free of dirt, mildew and other debris. Replace brittle or missing caulk at seams and in nail holes. Replace badly damaged boards with cement siding. Prime and repaint eroded finish, as necessary. Do not skimp on finish; apply two coats of paint. Paint brushes yield better results than rollers or pads.


Water seepage due to faulty installation causes most problems associated with hardboard siding. Water seeps through improperly caulked nail holes and joints or through cut edges too close to the ground. Water-logged siding eventually swells, bulges, mildews and, eventually, rots. Applying siding directly to masonry such as stone also allows water to seep in. However, properly installed siding rarely experiences problems.

Class-Action Lawsuits

Plaintiff's lawyers alleged that problems with hardboard siding resulted from inherent defects. Manufacturers blamed problems on faulty installation. Products cited in the suit included both lap and panel siding installed between 1980 and 1999. Manufacturers and plaintiffs settled the lawsuit in compromise.


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