Fiber Cement Siding What You Need To Know

The truth is fiber cement siding can be a better alternative to traditional wood siding if properly installed and well maintained.

Fiber cement siding that is not installed strictly to the exact specifications of the manufacturer is the number one reason for product failure.  This isn’t always a result of shoddy workmanship. James Hardie has over 83 specific guidelines that must be followed during installation to meet their requirements, and they change every year.

In addition to the install specifications changing every year, many homeowners ask their contractor to ignore some of the specifications because they don’t like the look a certain specification may create.

Hear are a couple examples:

Many homeowners do not want to see the wall flashing where their roof meets an adjoining wall. Almost every customer I have worked with has asked me to leave no more than ½” between the siding and the roof. I have to explain to them that this will completely void any warranty provided by James Hardie and will eventually cause the siding to fail. This is because water is the enemy of fiber cement. If water ever gets behind the siding, it will cause deterioration and mold.

There are specific clearance specifications for anywhere there is a potential for moisture to get behind the siding.

In addition to the recommended clearances, another specification many customers prefer their contractor ignore is how James Hardie recommends that seams are dealt with.

This is a specification that has recently changed. Up until a few years ago James Hardie recommended that all seams be caulked. This hid the seams pretty well.

Then James Hardie realized that the fiber cement would expand and contract with temperature changes differently than the caulking, and this caused constant maintenance in order to keep water from infiltrating the siding and causing deterioration and mold issues.

So now it is recommended that the installer simply install a piece of metal flashing behind each joint, which makes the seams much more visible and less aesthetically pleasing as seen in the photo below.

Here are a couple more things you should know about fiber cement before having it installed on your home.


Fiber cement siding weighs approximately 300 lbs per SQ (100 SF) On a typical home which has on average 25 SQ of siding, that is an additional 7,500 lbs or almost 4 tons of weight added to your house. If your house has any settling or foundation issues, this could create a huge problem.


Another issue that can be relatively common with fiber cement siding is mold growth. This normally occurs from joint sealing issues as well, as moisture is the main contributor to mold growth. The problem with mold growth can be fairly difficult to fix, as it can require home-owners to remove much of their siding, as well as remove the molded areas, depending upon the extent of the damage.

James Hardie is aware of this problem and for this reason has included the following exclusion in its warranty

The growth of mold, mildew, fungi, bacteria, or any organism on any surface of the siding and in this respect, ANY CLAIMS OF DAMAGE CAUSED BY MOLD OR MILDEW ARE EXPRESSLY EXCLUDED.

Not a maintenance free solution

With the recent release of it “Color Plus” technology, in which the siding is delivered painted from the factory many customers have been led to believe this makes for a maintenance free solution. Some of the most common complaints home-owners who have installed the Hardie product with the pre finished “Color Plus” is that the finish fades quickly, attracts dirt, and begins to chalk.  It’s not long before they are painting again. See how the warranty is written below to address (or not address) these issues.

Pro Rated 15yr Warranty that covers virtually nothing

“When used for its intended purpose, properly installed and maintained according to Hardie’s published installation instructions, the finish for a period of 15 years from the date of purchase: (a) will not peel (b) will not crack (c) will not chip

“During the 2nd through 15th year, the warranty payment shall be reduced by 6.67% such that after the 15th year no warranty shall be applicable.

“This warranty does not cover against fade or chalk of the finish due to normal weathering. Normal weathering is defined as exposure to sunlight and extremes of weather and atmosphere, which will cause any painted surface to gradually fade, chalk or accumulate dirt over time”

Class Action Lawsuits

Several class action lawsuits have been filed recently against James Hardie with regard to their fiber cement siding products. These lawsuits allege that in instances where the product has failed, James Hardie points to the written warranty that excludes most of the problems people are complaining about, and if the issue is covered, James Hardie will find an install specification that was not followed correctly and hide behind the following warranty condition.

“The product must be stored according to the manufacturer’s instructions at all times between purchase and installation. Installing wet product may result in staining or shrinkage, neither of which is covered under the terms of this warranty. The product must be installed according to Hardie’s printed installation instruction”

I think if most consumers who have installed James Hardie fiber cement siding on their home, had actually read the warranty instead of the sales brochure, they would have selected another product for their home.

If you have any questions regarding siding options for your home, please feel free to email me directly. If you found this article to be informative and helpful in making a decision on the type of siding you plan to install on your home, I would like to hear from you as well.

Steven Glaze

Smart Exteriors LLC