Fiber cement siding maintenance recommendations from Certainteed™, James HardiePlank™ & other sources.

This article describes steps to protect building siding from water damage, plant damage, weather damage in general, giving clearances as well as sealing & caulking advice. We include sources for back flashing and H flashing that can be retrofitted to leaky or loose building siding to improve its weather resistance. Page top photo: Tamlyn's back flashing product recommended when lap siding was installed.

Manufacturer's Advice for Maintaining & Protecting Fiber Cement Siding [CertainTeed & JamesHardie]

Adapted & excerpted from CertainTeed Corporation's "CertainTeed WeatherBoards™ Fiber Cement Siding Installation Manual" [5a] and from "Fiber Cement Siding Best Practices for Effective Job Site Management"[5b] and from JamesHardie Corporation installation instructions and bulletins for JamesHardie HardiePlank lap siding. [12][12b]

Moisture Management and Gutters & Fiber Cement Siding Avoids Water Damage

Water management is key to protecting every part of your home, including your siding. Each area of the country is affected by moisture, whether it’s an occasional thunderstorm, high levels of rainfall or heavy snow accumulations.

The resulting moisture has potential to cause damage if not managed effectively. We recommend protecting your home from rainfall with gutters and downspouts. Divert or remove heavy snow accumulations that may stand against the siding for extended periods of time. And you should always be sure that your drainage system is free of debris and working properly.

Details: See

• GRADING, DRAINAGE & SITE WORK
• GUTTERS & DOWNSPOUTS - No. 1 on the home inspector's hit parade of sources of water where we don't want it.
• FIBER CEMENT SIDING PAINTS - specific advice for painting fiber cement siding & for diagnosing paint failures on fiber cement lap siding installations
• SIDING DAMAGE by SPLASHBACK - a more severe problem where wood siding products are installed
• SIDING WOOD, FLASHING DETAILS - contains siding flashing details that work well for fiber cement and some other siding products as well

Shrubbery & Fiber Cement Siding, Recommended Distances

Proper moisture management also involves managing your landscape. Plants hold moisture, so any trees or shrubs that are close to your home should be trimmed periodically. Plants should not come into contact with your siding. Also, sprinkler systems should be adjusted to not saturate areas near your home.

• Details: see TREES & SHRUBS, TRIM OFF BUILDING and also see ALGAE, FUNGUS, LICHENS, MOSS.

Clearances for Fiber Cement Siding to Ground, Walks, Patios, Shrubs

Maintain required clearances and drainage slopes to ensure that moisture is diverted away from your siding at roof lines and ground level. Proper clearances include 1 inch from concrete, roof lines, patios, etc., and 6 inches from the finished grade. Landscaping should not reach the siding.

This refers to clearances from siding lower edge to ground, horizontal clearances to shrubs, &c. For details about siding gaps and clearances to other building components see Certainteed WeatherBoard fiber cement siding gap & caulking specifications

Re caulking Fiber Cement Siding - vs Installing H-Covers to Cover Siding Butt Joint Gaps

It is normal for building products located on the exterior of a home to expand and contract with temperature changes. To ensure a successful siding installation, you must allow for this movement during installation.

While CertainTeed WeatherBoards Fiber Cement siding does not experience the same rate of expansion and contraction as many other building products (such as wood), over time you may notice movement of the siding, specifically at the butt end/joints. This issue is mainly an aesthetic issue and should not create a condition that would cause long-term product failure. If you are dissatisfied with the appearance of the butt end/joint locations and wish to address them, CertainTeed recommends that you apply H-covers at the joint locations.

You will see vertical lines where each H-cover is installed, but then in our OPINION there were vertical lines already visible at the butt joint. And we agree with CertainTeed that this approach is likely to be more attractive than blobbing or smearing caulk into butt joint openings - a procedure that changes the texture of the siding and its coating performance or re-painting performance and appearance in a way that can be far more ugly, leaving roundish smears at every butt joint so treated.

Watch out: even the H-cover solution to siding board butt joint gaps is not without possible trouble. What are the chances that the plastic or aluminum of the H-cover will weather and change color at the same rate and in the same hue as the paint or coating on the siding boards? I'll bet zero. So over time these covers may become more noticeable.

Details about cures for the cosmetic problem of gaps at lap siding butt joints as well as for wall leaks at these locations are found at SIDING, FIBER CEMENT GAP CURES.

Question: how to fill holes, chips, dents in Fiber Cement Siding

2019/10/04 Jackie H. Smith said:

The Hardie Board siding was gouged in a deep, about 4-inch angular shape where the siding just had to be picked out. Home Depot employees suggested a cement material, which my husband used. When it dried, he sanded it with an electric sander. When it dried it looked like you would expect cement to look, rough.

It is on the back of the house and it will be painted to blend with the dark blue of the house. The only time that will be a problem will be if we should ever sell the house.

Is there a product for use with Hardie Board siding that would have worked better? The siding is smooth reverse board and batten style. Thanks.

Reply:

Thanks for an interesting question, Jackie.

OPINION: If this is a single-event, single point of damage on the home and if this is the biggest concern expressed by your home buyer we ought to be elated as it's certainly of no consequence: it's a minor cosmetic concern, not something indicative of a greater problem.

James Hardie, the makers of Hardie Board, noting that the siding is a cement board product, recommend patching damaged areas such as that you describe by using an acrylic mortar patching compound.

I'd like to know the specific product your husband used and I'd like to see a photo of the damaged / repaired area. You can post one photo per comment but of course can post as many comments and photos as you like.

There is a plethora of patching compounds on the market including cemetious ones and plaster-based patches. An example product from DAP and described as recommended for FC siding is shown below.

Here is an excerpt from what JamesHardie says about patching their Fiber Cement Siding

Fiber Cement Siding Repair or Patching

Re-applying caulking when it has begun to show signs of wear can help keep moisture from getting into the wall cavity. These areas include, but not limited to, penetrations, flashings, plank and trim connections, and in some cases, between plank joints.

NOTE: James Hardie recommends the use of caulks and sealants that remain permanently flexible. Look for the words “permanently flexible” written clearly on the label or in the accompanying literature. For best results, use an Elastomeric Joint Sealant complying with ASTM C920 Grade NS, Class 25 or higher, or a Latex Joint Sealant complying with ASTM C834.

Caulking/sealant must be applied in accordance with the caulking/sealant manufacturer’s written instructions or ASTM C1193.

Dents, chips, cracks and other minor surface damage in James Hardie siding and trim products can be filled with cementitious patching compound.

Refer to manufacturer’s recommendations for products that are compatible with fiber cement. [Emphasis ours - Ed.] - James Hardie Corp. retrieved 2091/10/04 original source: www.jameshardie.com/product-support/resource-center/fiber-cement-siding-maintenance

See details at SIDING, FIBER CEMENT BOARD REPAIRS

or for minor re-caulking repairs

see SIDING, FIBER CEMENT GAP & CAULK SPECS

...

Continue reading at SIDING, FIBER CEMENT BOARD REPAIRS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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SIDING, FIBER CEMENT MAINTENANCE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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