| In This
Article:
Cement backer board is installed over a
wood subfloor, and the joints are taped.
|
Related
Articles:
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| Skill Level: 3 (Moderate) |
Time Taken: 4 Hours |
By Bruce W.
Maki, Editor
 |
At this point, I had finished installing the 1/4" thick
WonderBoard
cement tile backer in the smaller bathroom. This was the first time I had
installed cement tile backer using screws and mortar to adhere it. |
| For each piece of WonderBoard I made a sketch on a file
card. |
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I did most of the cutting outside. I used a 4-foot drywall
T-square to layout long lines. |
| The first tool I used for cutting WonderBoard was a jig saw
with a carbide blade. This made a moderate amount of dust. |
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The carbide blade does not have teeth. Instead, it has a
rough coating of tungsten carbide, which is extremely hard. |
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The "thin-set" tile mortar, and the acrylic
admixture, which improves the flexibility of the mortar, among other
properties.
This large mixing paddle is very useful for mixing mortar. |
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I simply added the acrylic admixture instead of water...
... and let my large drill motor do the work. |
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This mixing paddle, about $17 at Home Depot, is an essential tool. I also use
it for mixing drywall compound.
| I used a 1/4" square-notched trowel for applying the
thin-set mortar to the sub-floor. |
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I scooped up some mortar and used the flat side of the
trowel to smear it into the cracks and grooves. |
| Then I "combed" the mortar with the notched side
of the trowel. |
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I applied only enough mortar to cover as much floor as one
3' x 5' sheet of WonderBoard. |
| I earlier cut the sheet to fit. (I tested the fit before I
spread the mortar.) Then I just laid the sheet on the mortar. |
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I walked on the WonderBoard to press it into the mortar. |
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These screws are made for installing cement backer board.
They have a special corrosion-resistant coating.
Notice the ridges under the screw head? They dig a hole in the cement
board for the screw head, so the head does not stick up. |
 |
| I drove in the "Rock-On" screws every 6 to 8
inches, into the floor joists where possible. |
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I drove the screws until their heads were buried at or below
the surface of the WonderBoard. |
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Obstructions like these toilet pipes can be a thorn in the
side. I covered the toilet drain with duct tape, so I wouldn't have to
scrape mortar off the PVC later. Note that the toilet flange has not been
installed yet. It was put in after the floor tile was completed. (View
that article). |
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To cut a hole in WonderBoard, I marked the location and
drilled a 3/8" starter hole.
Then I cut out the hole with the jig saw.
|
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| I staggered the joints from one row to the next, so the
seams would not line up. |
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The hole for the toilet supply line is far bigger than it
needs to be, but that will be hidden by the tile.
I did not cut out the hole for the drain until later.
|
| Halfway through this job I purchased an inexpensive
4-1/2" angle grinder ($20 on sale) and a not-so-inexpensive diamond
masonry blade (about $40). |
 |
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So for the remaining holes I used the diamond blade. This
worked fery well, but made a lot of dust and kicked out lots of fragments
of cement. Wearing safety glasses is necessary! |
| For some of the holes, I simply laid the WonderBoard right
over top and later went back and cut them out. Here I drilled small holes
up through the corners to mark their locations above. (I didn't want to
use the diamond wheel over my head and get covered with dust.) |
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Then I went upstairs and marked the outline of the hole and
cut it with the diamond blade. |
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When all the WonderBoard was installed I applied fiberglass
mesh tape to the seams and a coating of thin-set mortar. |
| Once the cement tile backer was installed, I used a chalk
line to make a base line for laying the tiles. |
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It was necessary to layout the base lines for the tiles before
installing the floor warming cables, because the cables will prevent me from
making a mark on the floor.
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Tools Used:
- Cordless Drill/Driver
- Jig Saw & Carbide Blade
- Angle Grinder & Diamond Blade
- Basic Carpentry Tools
- Drywall T-Square
- Framing Square
|
Materials Used:
- Cement Backer Board, ¼" Thick
- Thinset Mortar
- Rock-On Screws
|
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