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Re: mortar bedFrom: info@builderswebsource.com
Category: Tile/Marble/Granite
Remote Name: 63.198.181.43
Date: 05 Mar 2002
Time: 11:55 PM
CommentsLaying a solid, level mortar bed is essential to an enduring marble installation.
First, make sure the bed is substantially thick -- at least 3/4" or more. An inch or greater is better. Many people make it too thin to conserve height, but this results in many a failed installations and cracked marble. Assuming the subfloor is suitably stout, install two layers of 30-lb felt running each direction, being sure to overlap at the seams. Next, install wire stucco netting or similar galvanized hardware cloth using staples or galvanized furring nails.
Using a latex-based mixture, mix up plenty of mortar to a slightly damp consistency. Too wet a mixture will weaken the bed.
According to an April 1998 article in the Journal of Light Construction, tile expert Michael Byrne explains, "to the untrained eye, properly mixed deck mud looks like it’s far too dry to be of any use. Most tradespeople assume that deck mud should be plastic and pliable — similar to brick mortar.
But good deck mud should have just enough moisture to hold the mixed ingredients together when squeezed into a ball. This stiff consistency allows the mortar to be tightly compacted, which is critical for tile floors.
The working characteristics of deck mud also differ significantly from other types of mortar. Carve (rather than trowel) deck mud to final height, using the lead edge of my wooden float.
Students at our classroom facility in Clemson, S.C., are taught to test their finished floor setting beds by standing on the bed immediately after it has been floated and finished smooth. If the setting bed is mixed and compacted properly, the fresh bed should not show any heel marks after it’s been walked on.
Setting bed mortar contains two ingredients: Portland cement and sand. An acceptable mix consists of four to six parts clean, sharp sand to one part Portland cement. Sharp sand particles compact better than rounded ones.
I mix my deck mud in a large mortar box. I place all the sand in the box, sprinkle some water on top, and use a mason’s hoe to pull the sand back and forth to lightly coat the particles with water. I add the Portland cement and pull the mixture back and forth until it’s thoroughly mixed. Finally, I add just enough water to achieve the required consistency, then mix it thoroughly again."
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