New two-story house with fiber cement lap siding and white trim nearly finished

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Fiber cement · Cumberland, York & Sagadahoc

Fiber Cement Siding in Portland and Southern Maine

Fiber cement gives a painted-clapboard look without painted wood's upkeep, and it does not burn. In a freeze-thaw climate it lasts when the cut edges, clearances and paint schedule are handled right.

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Fiber cement combines cement and sand with cellulose fibers, formed into planks, shingles and panels that look like painted wood. It holds paint well, does not feed insects and is non-combustible. It is also heavy and brittle until it is nailed, and water is its weak point: soaked edges swell and the paint lets go.

On an old Maine village house it is often the material that satisfies a design review board while ending the repaint-every-few-years cycle of pine clapboards. Here is what makes it last in this climate.

Made for freeze-thaw

The largest fiber cement maker sells climate-specific versions of its siding. The one it describes for freezing temperatures, big seasonal swings and snow and ice, the climate it names as the northeastern United States, has a different surface and edge profile from the line made for the hot, humid South. Ask which version is being quoted; the product sheet says.

Freeze-thaw damage in fiber cement starts where water sits: at butt joints, at the bottom edge of the first course, and anywhere the siding touches a roof, a deck or snow banked against the wall. A plank that stays wet through a freeze can spall at the edge and shed its paint. Every rule in the next sections is really about keeping those edges dry.

Clearances at roofs, decks and grade

Fiber cement has to stay clear of anything that holds water against it. The maker's installation instructions show the clearances in a set of figures:

At least 1 inch, and often 2, between the bottom edge of siding or trim and a roof surface where a roof meets a wall.
A quarter inch above horizontal flashing.
Clearance above decks, walks and steps, and a larger gap above finished grade, which itself should slope away from the house.
A kickout flashing where a roof edge ends against the wall.

On a Maine house the grade clearance matters twice over, because snow piles against the bottom of the wall for months. Where the old siding ran down to the ground, the bottom course is often the rotten one, and the new siding should start higher.

Joints, nails and cut edges

The details that decide how fiber cement ages are small:

Butt joints are set in moderate contact, and the code requires a joint treatment behind or at each one: a joint flashing, caulking, or an H-joint. Flashing behind the joint is the method the maker recommends.
Nails go about 3/8 inch from the plank edge, driven snug, not overdriven; a nail sunk below the surface leaves a crack waiting to happen.
Studs no more than 24 inches apart behind the siding.
Every field cut is caulked, painted or primed, because the factory sealer is gone from that edge.

Planks are stored flat and dry; siding hung wet can shrink and open the butt joints once it dries. On a coastal job that means covered storage, not a pile on the lawn.

Primed or prefinished, and the paint schedule

Fiber cement comes primed for field painting or with a factory finish. Factory-primed planks must be painted within 180 days of installation, and the maker recommends 100 percent acrylic topcoats; stains, oil-based paints and powder coatings are out. A primed job is not finished until the topcoat is on.

Prefinished siding skips the painting crew, and its factory finish usually outlasts a field coat, but it is touched up only with the maker's kit, and caulking prefinished joints is discouraged because the caulk weathers differently from the finish.

Either way, plan on paint as maintenance at some point. The difference from wood is that a fiber cement wall holds its paint far longer when the wall behind it is dry.

Fiber cement and the review boards

Where a historic district limits materials, fiber cement often passes when vinyl does not. In Freeport's design review districts, fiber cement trim and siding that keep the old style and reveal need no certificate at all. Brunswick's Village Review Board weighs substitute materials one project at a time and would rather see original clapboards repaired. Bath wants any substitute to match the original in color, shape, size and texture.

The practical point: matching the exposure of the old clapboards, keeping corner boards and window casings at their original widths, and choosing a smooth face over a fake wood grain on a village house all help an application. We look at the street face of the house with the review standard in hand before we quote. Town-by-town historic rules.

Fiber cement or vinyl

Both are good claddings for this climate when they are installed well. The honest differences:

Question	Fiber cement	Vinyl
Look	Painted board, crisp shadow lines	Lap profile, thinner shadow line
Upkeep	Repaint eventually	Washing
Impact in cold	Resists dents	Can crack when brittle
Fire	Non-combustible	Melts and burns
Historic districts	Often accepted	Limited in several towns
Install labor	Heavier, slower, dust control	Lighter, faster

Fiber cement costs more to install. On a house in a review district, on one exposed to impact from ice and snow removal, or where the owner wants a painted look, it is often worth it. The vinyl page covers the other side.

Cutting it safely

Fiber cement contains crystalline silica, and cutting it makes fine dust. Installers use shears or a dust-collecting saw, cut outdoors with the dust blowing away from the work, and wear respiratory protection when the method calls for it. On a tight city lot in Portland or South Portland that also means setting the cutting station where the dust does not drift into a neighbor's open window.

Indoors, nothing is cut. Planks are handled on edge so they do not snap, and corners are protected until they are on the wall. A chipped corner is a callback in three winters, because that is where water gets in.

Trim, corners and the window surrounds

Most of what makes a fiber cement house look right, or wrong, happens at the trim. Old village houses here have wide corner boards, deep window casings and a frieze board under the eaves, and covering them or shrinking them is what makes a re-sided house look flat. We match the old widths wherever the wall allows it.

The trim itself can be fiber cement, cellular PVC or wood. Each joins the siding with a gap that gets sealed, and each window head gets a drip cap or flashing so water running down the wall is thrown clear of the casing below. Where the siding is thicker than the old clapboards, the window casings may need to be built out so the planks still die into them properly.

On a pre-1978 house, removing painted trim falls under the federal lead-safe rule; the containment goes up before the first casing comes off. What that involves.

Gothic-style house with carved bargeboard trim, a pointed window and diamond-pane sashes

Common questions about fiber cement siding in Portland

Does fiber cement crack in freeze-thaw weather?

It holds up when its edges stay dry. Problems start at butt joints, bottom edges and places where it touches a roof, deck or banked snow. Proper clearances, joint flashing and sealed cuts are what prevent them.

How long before fiber cement needs painting?

Factory-primed siding must be topcoated within 180 days of installation. After that, or with a factory finish, repainting is periodic maintenance, and a dry wall holds its paint far longer than painted wood does.

Is fiber cement allowed in historic districts here?

Often. Freeport exempts fiber cement of the same profile from design review, and other boards consider it as a substitute. Each town's standard differs, so the address gets checked before ordering.

Is fiber cement heavier to install?

Yes. It is heavier and slower than vinyl, needs dust control when cut and careful handling so corners do not chip. That labor is part of why it costs more.

Can fiber cement go over old siding?

It needs a flat, solid nailing base and enough stud penetration, so going over uneven old clapboards rarely works well. Most fiber cement jobs start with a tear-off and a new barrier.

Does fiber cement need a permit in my town?

The material does not change the answer; the town's rule on re-siding does. Raymond and Cape Elizabeth exempt a re-side, while Scarborough and Falmouth require a permit for any repair or alteration. Each town page has the wording.

Where we work

Fiber cement siding across greater Portland and southern Maine: Cumberland, York and Sagadahoc counties, from the islands of Casco Bay to the Sebago Lake towns and the New Hampshire line. Each city has its own page with the permit rule and code edition that apply there: