How to Cut Cement Board and Hardie Backer

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Cement board​ is one of the most useful home improvement inventions of the 20th century. ​It is used as a tile backing board in places where moisture is common, such as your kitchen or bathroom. 

​Once you learn how to cut cement board, you will be able to add walling and tilework to your home. Here is our complete guide on how to ​cut ​cement ​board for your next kitchen or bathroom remodel.

An Overview of Cement Board

For starters, let’s make sure we’re all talking about the same product.

Cement board is interchangeably referred to by quite a few names, and it is worth listing those out.

For the sake of this article, cement board is the same product as:

  • Hardie Board
  • Hardie Backer
  • ​Durock Board
  • Backer Board
  • CBU (Cementitous backer unit)
  • Cement Backer Board

​At the end of the day, all of these are a brand or variation of cement board.

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Man uses a jigsaw to cut a circle in cement board

Cement Board vs ​Hardie Board

​​Hardiebacker or board is the top brand selling cement board. When you hear the term “Hardie board”, it is referring to a specific brand of cement board.

Hardiebacker offers a premium cement board product with a lifetime warranty and technology that includes MoldBlock TM.

Hardiebacker ensures mold will never be an issue on your cement board by not using any paper in their product. It is 100% Portland cement and finely ground sand.

It is also free of gypsum, asbestos, and formaldehyde.

One perk of the Hardie board is that it comes standard with perforated groves on standard lines, and because of that, cutting the Hardie board is easy.

Cement Board vs Drywall

​​A cement board is actually quite different from drywall, with both of them being used for other purposes. However, to the untrained eye, they can be easy to confuse.

  • The cement backer board looks and feels somewhat like drywall. You can think of it as its cousin.
  • The difference is that drywall is made of gypsum covered with paper, and ​cement board is made of a combination of cement and reinforcing fibers.
  • This means that unlike materials like drywall, plywood, or green board, there is no organic matter in the cement backer board. Unlike drywall, ​cement board has no gypsum, asbestos, or formaldehyde.
  • This also means cement backer board will never mold, rot, shrink or decompose due to the presence of organic materials.

​A cement board is waterproof, which means that it will resist water, making it the perfect substrate to sit behind the tile.

If your project actually requires drywall (and not cement backer board), make sure to read our article on sheetrock vs. drywall

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Cement Board vs Greenboard

Even green board, which is more durable and resistant than drywall, is not recommended for use in showers and other places where there is constant water usage. For these purposes, a cement backer board is perfect. That is why cement backer board is mainly used as a substrate for tiling.

Since tile is widely used in bathrooms, kitchens, and other places where there is constant moisture, it has become the go-to solution when tiling.

​Applications

Now that you know the differences between cement ​board vs. Hardiebacker, drywall, and green board​, let’s talk about where is it best to use this product.

Cement backer board has the great advantage of being totally inorganic. As mentioned earlier, it will not rot, warp, mold, or deteriorate when wet. Cement board is best used where water could be present.

Obviously, wood is not an ideal material to use in places with a lot of moisture. Neither is drywall. If you use any of these, you might have issues with mold.

Where to Use

Cement board is also used as a substrate for manufactured veneer stone. In contrast with more traditional materials like drywall, cement backer board won’t soak in moisture from the mortar under the veneer stone-like drywall will. 

Cement board offers considerably more strength when compared to drywall. It provides builders with the easy-to-install equivalent of a concrete subfloor. It is a very hard, very flat surface. 

Tiles and other materials can easily be laid on it with no concern for the presence of moisture on the substrate.

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Walk in shower is prepared for cement board

While perfect for tiles, professional builders often use cement boards for other kinds of floors, countertops, backsplashes, and even walls.

​Types and Sizes

There are two basic types of ​cement board​: one is hard and heavy like concrete, and the other is softer and lighter.

Cement backer board comes in several thicknesses, much like drywall​, and is generally made in thicknesses of 1/4”, 7/16”, 1/2”, and 5/8”. 

  • You’ll use the thinner boards in areas like countertops​.
  • You’ll use the thicker boards behind the shower and kitchen walls. 

Cement backer board​ usually comes in one of two sizes: 3’x5′ and 4’x8′.

​It’s relatively inexpensive for most DIY jobs around the house. For example, a 3’x5′ sheet of 1/4” backer board runs around $10, and the same size in the 1/2” thickness runs around $14.

​​How to Cut Cement Board

​No matter what, whenever you install backer board, you’re going to have a variety of cuts to make, and you might start googling “how to cut backer board”, “cutting Hardie backer”, or “how to cut concrete board.” There are plenty of different ways to cut ​this type of board, ranging from very easy to very precise.

The best way of cutting ​depends on the tools you have at your disposal, how much time you have, and how precise you need to be. We’ll go through each of the most common ways ​for cutting ​backer board below. 

​Note: If you want to learn how to cut Durock, you can follow the same process. Durock is simply a brand of ​cement board.

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Method One: Cut with ​Score and Snap​

The simplest way to cut concrete wallboard or cement backer board is not to use power tools at all. Similar to the way drywall is cut, it is possible to score the cement backer board and snap it along that scoreline.

It is possible to use a drywall knife to score a cement backer board. But it will wear down the blade and take some effort.

A better option is to pick up a carbide-tipped score knife. These tools have a very durable scoring tip, which can be used to easily score cement backer board.

Man uses the score and snap method to cut cement board
  1. Begin by laying your backer board out on a flat surface and mark the line where you’d like to score the board. You can do this with a carpenter’s pencil or use a chalk line.
  2. When it’s time to make the cut, set a straightedge across your sheet. Use a level, yardstick, or a leftover piece of scrap lumber.
  3. Kneel on one end to ensure the straightedge does not move, and firmly draw the scoring tool along the line.
  4. Holding the tool against the straight edge, you can use it as a guide to ensure a perfectly straight scoreline.
  5. Repeat the movement three or four times to get a nice, deep score cut into your cement backer board.
  6. Once you have a sufficient score groove, pick up the cement board. Press with your knee and pull. The backer board should snap cleanly along your scoreline.

A cement board has fiber inside it for structural strength, so you can use a utility knife to cut through this mesh to separate your two pieces. Using a rasp, you can easily smooth the rough snapped edge.

​Method Two: Cut with a ​Circular Saw

​Scoring and snapping can be tricky, especially with thicker cement boards. Not only is it difficult to hold a straight line for the entire cut, but cutting by hand takes a long time if you’re cutting a lot of cement boards.  

Circular saw on a table

When scoring and snapping aren’t ideal, it is possible to use power tools to cut your fiber cement backer board. ​We’ll review several power saws that you can use, starting with the circular saw. 

As long as you’re making a straight cut, the circular saw makes for a great method to cut ​cement backer.

A word of caution: cutting a Hardie Backer board ​with a saw produces fine silica dust that is crystalline in structure. Such silica dust has sharp edges and will irritate eyes and lungs. 

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​Again, you should always wear a respirator mask and eye protection (e.g., eye goggles) when cutting cement board. ​The good news is that eye goggles aren’t particularly expensive. It’s a good idea to make your cuts outdoors, or open doors and windows.

This is dangerous​, so make sure to read the safety instructions for your circular saw and follow them to a tee.

For simple straight cuts, you can fit your circular saw with a carbide-tipped wood blade, and use slow, even pressure when you make the cut. ​Make sure to use a blade with the fewest teeth you can find.

When you’re cutting wood, you typically want more teeth in your blade so to make for a cleaner cut. But when cutting cement backer board, more teeth in the blade aren’t necessary and will just make more dust. 

A carbide-tipped blade with as few as six teeth will cut a cement backer board smoothly and quickly.

  1. Lay your backer board out on a work table or between two sawhorses. Unlike score and snap, you’ll need to use a surface that allows for a saw blade to go through the board.
  2. Mark ​where you’d like to cut the board.
  3. Like the score and snap method, set a straightedge across your sheet. ​
  4. Wait for the saw blade to warm up and come to full RPM before starting your cut.
  5. Work slowly through the cut, ensuring that the straight edge doesn’t slip or move while you’re sawing.

Method Three: Cut with a ​​Jigsaw

​If you’re not cutting a straight line, ​use a jigsaw with a carbide-grit blade or a metal-cutting one installed.

Cutting curves is much easier with a jigsaw, and the preferred option in this case to a circular saw. With that being said, cutting circles by hand can be tough, especially when precision is required.

Man uses a circular saw for cutting cement backer

This method is slow and produces a little dust. ​After several cuts, you’ll probably need to replace your blade. Still, if you need to cut a smooth curve, the jigsaw is probably the best way to cut a Hardie Backer board for you.

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​Don’t forget about a cord-free jigsaw option, either. If you have one that is powerful enough, this can make the project go a little faster and make it a lot more convenient.

​Method Four: Cut with an Angle Grinder​ or Tile Saw

It is also possible to cut a Hardi Backer board with an angle grinder that has been fit with a diamond cutting wheel. However, the angle grinder makes a lot of dust and is a little more difficult to control than a circular saw.

You really only want to use this method for fast cuts, as your lines won’t be as straight as with other methods. 

If you have a wet saw for cutting tile, you could use this for cutting your Hardie board, as the abrasive blade is constantly bathed in water, resulting in a clean cut with no dust.

You might not find it worthwhile to get out your tile saw for this, but if you have a lot of cuts to make, it might be worthwhile.

This method probably produces the least amount of dust out of all of the ones listed. 

​How to Cut Circular Holes in Cement Board

When installing cement board around a toilet, faucet, or other pipe fittings, you may discover that you don’t know how to cut a hole in a cement board. As such, you might start wondering what the best way to cut concrete board is. Similar to cutting circles in wood, there are a few tricks available for those who need to do this.

This method is different than cutting a circular pattern in your backer board. This method is specifically focused on how to cut a hole out of the cement backer.

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If the hole is small enough, the simplest way to cut a hole is to use a carbide-tipped hole saw and a highly reviewed and rated drill. ​

Different sizes and kinds of drill bits
  1. First, draw the outline of your hole on your cement board with a compass. Or, you could trace a pipe fitting or other circular object of the proper size.
  2. Using a 1/4” masonry bit and a cordless drill, drill a bunch of holes along the edge of this circle. Think of making a perforated “dotted line” along the edge, so drill as close to the other holes as you can. 
  3. Once this is done, using a hammer, lightly tap on the center of your circle.
  4. After a few taps, the backer board should snap along your dotted line.
  5. From here, you can finish the cut with a utility knife and smooth out the rough edges with nippers.

We mentioned it above, but a jigsaw is also the perfect power saw to use for cutting a circle.

Conclusion

When you are considering ​the best way to cut ​cement board, first evaluate and ensure you are using the proper substrate.

The process of cutting Hardie board depends greatly on what tools you have, how accurate you need to be, and how fast you want to go. While power saws make it a lot easier, it is possible to cut ​cement boards by hand.

Either way, follow the steps we’ve outlined in this guide on how to cut fiber cement board and Hardie board. And remember to follow all safety instructions!

An expert at home repair, remodel, and DIY projects for nearly 40 years. His first experience came in completely restoring an antique home. Completely redone from the inside out, and restored to its original form, the home is a featured design by renowned Southern California Architect Cliff May, considered to be the father of the California Ranch Home. Now Dennis spends his time on fine woodworking projects and tool comparisons.