A fireplace used to take a true craftsman to build and often only installed when the house was under construction. Today the newer prefabricated fireplace units make it easy for anyone to have the warm toasty fire to warm their hands on a cold winter night. Whether you have a finished fireplace and want a change, or just installed a prefabricated one and need to cover it, natural products are the most popular today. Marble, while extremely popular now, never loses its appeal as a sign of good taste and opulence.
Pick out the design for laying the marble fireplace surround. You'll need to take the measurements that coincide with that design. It's easiest if you draw a picture of the area with the design and put in the dimensions. When you buy the marble, allow the salesperson to help you with the amount of marble and materials you need. Buy a stress crack membrane to join areas where there are two different types of underlayment like where the metal on the prefabricated fireplace meets wallboard. These two types of materials have different expansion rates when heated, and that causes cracks without the membrane.
Verify the floors and other surfaces are level. If you find an area that has a dip in it, fill it in with a coat of thinset. Any time you put marble over masonry, make sure you put a layer of thinset on it to even the surface before you move to the next step. Clean any cement and wood thoroughly before you continue.
Check to see if the area is sturdy. Make sure that any wood subfloors are in good repair. If you have masonry that you're trying to hide because it's in disrepair, you may not have to tear it out before you lay the marble. The stress membrane works great in these areas too, unless the masonry's really bad. Put the stress membrane down on wood subfloors. The only place you shouldn't put the stress membrane is on the facing of the fireplace. The membrane's only for temperatures up to 121 degrees C, and that area is too hot. Allow all repairs to dry.
Lay the area on the floor, the hearth, first. Use a trowel to put a layer of thinset down on the area. If your base is wood, you should already have a layer of membrane that's applied and dried. Apply a coat of thinset over the membrane as the adhesive for the marble. Lift the marble hearth into place. You'll need extra help for this. A large piece is fragile and expensive, so you don't want to lose your investment by dropping it. Slide the marble in place, and use a rubber mallet to tap it and release any trapped air bubbles.
Make the most visible areas perfect by starting there. Usually this means that you start at the top and work down, with smaller half marble tiles at the base. When you start at the top of a wall, it presents a bit of a problem so you have to get creative to hold the marble in place. A ledger shelf is the answer. This is a piece of wood that the marble tiles sit on until the wall dries. If you're applying it to sheet rock with studs behind it, you can simply nail it on the wall. Start two rows from the top and use spacers between the first and second row. If you don't have a wall with studs behind it, put legs on the ledger shelf to hold the marble in place. If you need to cut the marble, use a wet saw.
Brace large pieces with wood and heavy weights to hold it in place. Put a wood brace that starts at the top of the large section and ends on the floor with a heavy weight behind it. You may need several braces. Allow all the tiles to set up overnight before you attempt to grout.
Seal the marble before you grout. Even though it's an extra step, it prevents a lot of scrubbing to remove embedded grout. Let this dry. Apply the grout and gently wipe away excess. Once it's dry, use a soft dry cloth first to wipe as much grout as possible, then use a damp cloth. There will be a haze left when it dries. Wipe first with clean dry cloth and then use a damp cloth again. The most difficult part when you install marble for your fireplace surround is cleaning the tile. At this point, you're ready for the project to end. It's important to do a thorough cleaning. Once it's thoroughly dry, use a grout sealer. ·
Wear a mask when mixing the thinset to avoid breathing the dust. Rubber gloves are also good to use when working with the thinset. If you cut any pieces of marble, wear safety glasses.