What Is Durock?

Jessica Hobby
Jessica Hobby
Durock can be scored with a utility knife to make it break easily.
Durock can be scored with a utility knife to make it break easily.

Durock® is a brand of cement backer board manufactured by the United States Gypsum Company, which is a subsidiary of USG Corporation founded in 1901. Cement backer board is most often used as a subfloor or wall base when installing ceramic, porcelain or stone tiles. Cement backer board is called by a variety of names such as cement board, backer board or tile underlayment. Additionally, some refer to all cement board as durarock, which is a metamorphosed version of Durock®. It is very similar to the way most people refer to all plasterboard as Sheetrock®, which is actually another one of USG’s popular products.

Durock® is composed of an aggregated Portland cement core which is coated with a glass-fiber mesh on one side. The smooth side is used for adhesive applications while the mesh side is used for thinset mortar or mastic application. Durock® can be scored with a utility knife so it breaks easily for do-it-yourselfers who don't have a saw. When installed, the seams should be scattered. Additionally, the seams must be taped and prefilled with mortar for the best results.

Backer board provides a level and supportive base for glass and ceramic mosaics, tile, stone and brick. Whether using cement board in new construction or remodeling, it may be installed over a wood or steel frame to walls, floors, soffits, partitions, countertops and ceilings. The cement board is fastened with cement screws, self-drilling fasteners or nails.

Durock® cement board comes in two sizes. The 4 inch x 4 inch is 5/16-inch wide and the 3 inch x 5 inch cement board is ½-inch wide. The thinner Durock® offers less support so it may be used for thinner tiles, while the thicker board will be needed for thicker tiles and floors with inadequate support because of the direct pressure applied when people walk on them. The different thicknesses also help maintain even transition areas on the floor.

One of the most common areas to use Durock® is in the bathroom because it is mold and moisture resistant. Cement board is necessary where water may run on the floor, but it is mandatory for tiled showers or tiled areas above a bathtub. Durock® may also be used in pool areas or saunas. It also has applications in the areas around fireplaces and wood burning stoves. The product is noncombustible and it will not swell, soften, decay, delaminate or disintegrate according to the manufacturer.

How To Cut Durock?

Thanks to the versatility of Durock, there are a few different ways to cut, prepare, and install it. Depending on the purpose of your cuts, you will likely be readying the cement board for laying, hanging, or making cutouts for fixtures. For best results, specific power tools and safety coverings are ideal for keeping your work area neat and injury-free.

Materials 

First, determine how much and which thickness of Durock you will need for the job. Then, gather the rest of the necessary materials set up your workspace.

Cement Board Specialties 

When you purchase the Durock, you need to consider how much is necessary to complete the job in mind. The required other supplies will likely be nearby for ease of purchase.

  • Glass fiber tape 
  • Hot-dipped galvanized roofing nails, wood screws, or steel screws 
  • Power drill 
  • Specialized drill bits 
  • Utility knife 
  • Wood rasp 

Tile and Grout Specialties 

Depending on the type of tile you choose for your project, specific grouts and mortars might be more or less appropriate.

  • Adhesives, mortars, and grouts
  • Tile cutter 
  • Nipper
  • Noticed trowels 
  • Straight edge 

Household Standards 

Other tools that make cutting Durock easier are typically in drawers or toolboxes around the house. No special trips or orders will be necessary to find what you need.

  • Level 
  • Tape measurer 
  • Caulk and caulking gun 
  • Hammer
  • Sponge
  • Squeegee
  • Safety glasses 
  • Face mask 

Step 1: Determine Your Purpose

First, decide what purpose your Durock is fulfilling. Will it be for the wall, the floor, or the ceiling? Once you have determined the purpose, lay your cement boards to take accurate measurements.

Step 2: Measure Twice

Take measurements for the appropriate sizing and mark where to cut in pencil.

Step 3: Cutting Options

For thinner pieces of Durock, like those for walls and ceilings, you will likely be able to score the cement sheet with your utility knife and then snap the pieces off as you need. However, for thicker floor pieces, it is more efficient to use a circular saw to make light work of the process.

For cut-outs, the options are similar. You can mark and score the areas that need to be removed for fixtures and then punch them out by hand or with a hammer. An alternative is to buy a hole-saw bit in the size you need for the fixture, attach it to a power drill, and make the cut that way. If you routinely DIY projects, a standard size hole-saw bit is worth the purchase and is useful in many different applications.

Step 4: Follow-Up and Clean-up 

After cutting or snapping, the edges of the Durock may be jagged or uneven. Use the wood rasp to smooth the edges and make the attachment more seamless.

Before going any further, clean up any dust or debris accumulated in the area. Cleaning as you go will make the work area safer.

How To Lay Durock for Tile Floor?

Laying Durock for tile floor starts with choosing the thicker option for the cement board. The thicker choice is ideal because floors are under daily pressure from high traffic and water contact.

Adhesive and Trowels 

To correctly install the Durock in preparation for a tile floor, begin by adding adhesive or mortar to the back of the subfloor. If using adhesive, take care to utilize a ⅝” V-notched trowel for the job. If using mortar, use a ¼” square-notched trowel to lay the Durock. When attaching the subfloor and cement board, be sure to leave a small gap when fitting ends together. Fasten the board down by using the appropriate nails or screws.

When you are ready to lay the tiles, apply the mortar or adhesive with a notched trowel in small increments. Laying tile down as you go, slide, then push the tile into place to avoid overfill. Tile spacers help maintain uniformity in installation. If you choose not to use spacers, still insert shims under the row of tiles by the bathtub to make a caulk joint for an extra tight seal.

How To Hang Durock Cement Board? 

Hanging Durock is similar to the process of hanging drywall or sheetrock boards. The cement boards are cut to size and then installed to the studs in the walls rather than attached with adhesive or mortar.

To create seamless joints, carefully pre-fill all the joints when you seal the inside and outside corners, and then add the glass fiber tape over the top. If there are sparse areas, fill again until a substantial seam is constructed. Cover the glass fiber tape with mortar and then level for smooth walls to finish the job.

How To Cut Durock

Durock is a type of cement board that’s most often used in wet environments as a substitute for sheetrock. It’s an excellent material for use on floors, walls, and counters in kitchens, bathrooms, and basements. And, if you tend to take on DIY ventures pretty often, you'll be happy to know Durock is relatively easy to cut to size for all of your projects.

There are two ways to cut Durock: scoring and snapping or with a saw or drill. Scoring and snapping is quick and easy, but using a power tool offers its own benefits, too.

Option 1: Score-and-Snap

Scoring and snapping Durock is a quick and straightforward method of cutting cement board that will let you cut your sheet to size without breaking out any power tools. This method is ideal if you're doing a simple job that doesn't require anything more than straight cuts.

Materials

  • Carpenter's pencil
  • Straight edge
  • Utility knife
  1. Clear a space across sawhorses, on a utility table, or on the floor that will hold your Durock, then draw a line where you'd like to cut the board.
  2. Place your straightedge along the line you just drew and score it with your utility knife. Then, repeat your cuts two to three times to ensure the score is deep enough to allow you to properly snap the board.
  3. Stand the board up, then press your knee to the backside of the scoreline and press. 
  4. Once the Durock has snapped, use your utility knife to finish cutting the mesh.

Option 2: Saw or Drill

Power tools will allow you to achieve smoother and more precise cuts. They'll also let you cut holes and cutouts easily. Whether you use a circular saw, jigsaw, drill, or hole saw will depend on your purposes, but all will give you smooth cuts.

Materials

  • Circular saw, drill, hole saw, or jigsaw
  • Woodcutting blade (if using a circular saw)
  • Masonry bit (if using a drill)
  • Metal-cutting or carbide-grit blade (if using a jigsaw)

If you want to cut straight lines, a circular saw is your best choice. Simply trace your line just as you would if you were using the score-and-snap method, then follow the line with your saw. Be sure to use a blade with the least number of teeth to limit the amount of dust.

If you need to cut out smaller sections of your Durock, you'll want to use a drill with a masonry bit, a jigsaw fitted with a metal-cutting or carbide-grit blade, or a hole saw.

A masonry bit will be best for holes, but a jigsaw will let you customize your cutouts a bit more easily. If you need perfectly round holes, your best bet will be a hole saw because it doesn’t require you to outline the circles perfectly.

As with the other two methods, be sure to mark your board before you begin cutting.

How To Install Durock 

Durock makes an excellent backing for ceramic tile but only if you install it properly. If you don't, you'll risk ruining your tile job.

There are several steps you'll need to take before you can install your Durock.

  1. Check for and straighten crooked studs.
  2. Add blocking between studs and additional studs as necessary.
  3. Waterproof your walls (if necessary).

The process for hanging Durock is relatively simple, and once you get the hang of it, you'll be able to complete the job relatively quickly.

1. Cut Your Boards

Measure your boards and cut them to size using your saw or utility knife. Don't forget to measure twice before cutting.

2. Place Your Boards

If you're using thin-set mortar adhesive, place your boards with the rougher side facing outward. If you're using latex mastic to install your board, you'll want to place the smooth side out.

3. Hang Your Boards

Screw your Durock to your wall using 1-¼" cement board screws. Space the screws out by 8 inches along each of the studs, leaving one inch of space between screws and outer edges.

Is Durock Waterproof?

Durock is an excellent choice for bathroom or kitchen applications because of its waterproof qualities. However, although Durock won't degrade if water soaks into it, it doesn't act as a water barrier. In other words, you'll need to do additional waterproofing if you want your construction to be fully waterproof.

As with any cement board, you'll have to add a moisture barrier to protect the inside of your walls. Durock makes tile and waterproofing membranes to supplement the waterproof qualities of the cement board itself.

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Discussion Comments

anon939066

What side is the rough side of durock? Is it the side with the writing or the plain side?

anon77795

Don't you mean 4 ft x 4 ft or 3 ft x 5 ft rather than "The 4 inch x 4 inch is 5/16-inch wide and the 3 inch x 5 inch cement board is ½-inch wide"? Also I think there is a newer lighter version that can be single side scored for breaking.

Mythoughts

Durock should not be installed with standard self drilling fasteners or nails. Either use hot dipped galvanized roofing nails or screws made specifically for this application.

Cement board screws have a corrosion resistive coating as well as a wafer head design with counter sinking ribs to allow flush installation.

Regular self drilling screws will strip out, they will not countersink, and will also be prone to rust.

It should also be noted that only fiberglass mesh tape should be used in the taping process. Also to cut the Durock, both sides should be scored with a utility knife to break the board smoothly.

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    • Durock can be scored with a utility knife to make it break easily.
      By: J and S Photography
      Durock can be scored with a utility knife to make it break easily.