Q&A / 

Fiber Cement Siding Installation Tips

DEAR TIM: My New Years resolution is to install new lap siding on my home. I've narrowed it down to fiber cement siding because of its durability and good looks. However, I'm stumped as to how to install it. It seems like it's so brittle that it would crack if you try to nail it. What's the easiest way to cut it? How do you nail it? What other secret tips can you share about installing fiber cement siding? Amy S., Niagara Falls, ON Canada

DEAR AMY: I sure understand why you're attracted to fiber cement siding. It has so many positive qualities, I don't know where to begin. Many people are unaware that it's been around for well over one-hundred years.

In many older cities and towns around the USA and Canada, I can show you homes that were built in the early 1900's that still have the original fiber cement siding on them. The best part is that it looks like the day it was installed!

This handsome siding is not wood. It’s made primarily with Portland cement with tiny wood fibers as a binder. Photo Credit: Tim Carter

The original fiber cement siding was made a little differently than today's products. Years ago the fibers used in the siding were asbestos. When you combine asbestos with Portland cement, you create a product that's virtually indestructible. It won't burn, it's insect proof, water will not harm it, and it's basically thin sheets of rock. We all know how long-lasting rock is!

But as you point out, rock - and fiber cement siding, is somewhat brittle. The original fiber cement siding was more brittle than the products you buy today. If you purchase 12-foot lengths of fiber cement siding and hold it flat in your hands, you'll quickly discover it acts much like a piece of wet spaghetti. It bends easily. However, you can crack it if you're not careful.

The first thing you need to do before you install this magical siding is to take a few minutes and read thoroughly the written installation instructions produced by the manufacturer. By doing this and following their instructions, you ensure that you'll not void any warranty that comes with the product. That's very important.

Be sure to wear all of the safety gear, including approved dust masks, that the manufacturer recommends. The dust that's created when cutting fiber cement siding contains silica. Silica is not a good thing to get into your lungs.

I've cut thousands of feet of fiber cement siding using an older electric miter saw outfitted with a carbide blade. You can use an abrasive blade made for cutting masonry, but I find that creates even more dust.

The silica dust will significantly shorten the life of the electric motor on any tool. You might want to go online to the classified ad websites and buy a decent used saw for this job. If it still works at the end of the job, you can resell it or give it away for free.

I suggest cutting the material outdoors so the dust dissipates. Set up the saw so that you're always upwind of the saw blade. You want the dust to blow away from you at all times. I've even set up a powerful fan to create wind on calm days.

Believe it or not, using proper siding nails as called for by the siding manufacturers, you can nail along the top of the siding without cracking it. You need to be at least 1-inch away from the edge. You'll discover nails at the top corners of the siding will need a pilot hole to prevent cracks. You can buy a small 1/16th-inch-diameter masonry bit that drills a perfect pilot hole.

One of the benefits of using fiber cement siding is blind nailing. The siding is so rigid that you can nail along the top edge of the siding for certain widths and the siding won't flap in the wind or curl. The nails are covered by the next piece of overlapping siding.

This is a huge advantage as you don't have to see any nails or you don't have to countersink and putty them. I love blind nailing siding. The only nails visible are those holding the last piece of siding at the top of the wall.

When you have to butt two pieces of siding together on a long wall, you absolutely must install a piece of flashing under the two pieces of siding. I usually cut a piece of 40-pound tin about 1.5 inches wide and a little longer than the pieces of siding are wide.

The metal strip is placed behind the two pieces of siding that are going to butt together. It overlaps the piece of siding below the butt joint, but stays slightly above the bottom of the two pieces that cover the metal. You don't want to see the bottom of the metal below the siding once it's installed.

Drive one nail at the top of the metal flashing after sliding it under the end of one of the pieces of siding so it stays in place. Don't be tempted to use tar paper for flashing as the heat of the sun can cause asphalt to drip from the felt paper causing ugly stains to appear.

You can watch videos about siding tips by simply typing "siding video" into the search engine at www.AsktheBuilder.com.

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