Do not place cement board into the shower pan mortar bed. 1. I generally silicon tiled corners. If water gets to the cement board, capillary attraction can cause water to wick up into the cement backer . Cut the Boards Cut the boards for the remaining sides of the tub and install them in the same. i recently replaced my tub surround with tile. Then, how big of a gap can I fill with caulk? i meshed all the seams and filled with mortar. Measure the size of the gap that . 6. Caulk the gap Probably the simplest way is to caulk the gap with 100% silicone or a urethane sealant. The gap is easily filled with the tile wall grout . Step 5 4. 1 yr. ago. Install the sheet 1/8 inch above the first, leaving room for thin-set mortar with will provide strength to the seam. above the tub lip to allow for movement of the tub and floor. Mix and Apply the Mortar. The tub has about a 1/2 - 3/4 in "ridge" on the three wall sides that the backer board is resting on. Drive the screws in so that the heads are slightly below the surface of the backer board sheet. The 3' isn't "code" either. This small gap is created by the compressed thickness of the organic mastic or the cement thinset used to attach the tile to the backer board. What do you do with a gap between tub and cement board? Tile Around Tub With Lip. The greenboard is gone, I have placed concrete backerboard on the back and the long side of the tub. clearance gap between the floor, tub or shower receptor base and the cement board. 2-inch alkali-resistant mesh tape is applied at every backer board seam and corner. Definitely use cement board instead of green board. You need to determine how the water is getting into the space behind the tile. Applying pressure makes the tiles stick. It is normal for there to be a gap below the backer board and the tub. First, you would waterproof with your favorite liquid waterproofing membrane of choice. The cement board should be plumb, hence the need for shims sometimes. Fill the gap between the tile and the tub with caulk. You can then caulk the 1/4 inch gap between the bottom of the cement board and top of the tub. Cement Board Detail above the lip of the tub. Measure the size of the gap that needs to be filled. Mixing a batch of thin-set mortar is the basic step in the installation of cement boards. i left expansion gaps on all the corners but did not leave spaces between the individual pieces of board. The tiles will hide the joint and make the job of finishing the . Then a coat of thinset gets flat troweled over the seam. You can then caulk the 1/4 inch gap between the bottom of the cement board and top of the tub. above the tub. Drill cement board screws through the backer board sheets every 6 to 8 inches. Finally, fill the gaps between the tile and tub with caulk. When installing cement board above a bath, leave at least a inch gap between the tub and cement board to prevent the wicking of moisture. 2. The corners and edges of the sheets should not touch one another. Once all the boards are screwed to the framing, fill the joints with water resistant material. The greenboard is gone, I have placed concrete backerboard on the back and the long side of the tub. 2. Space between plywood supports is not to exceed 16" on center. Plan the installation so the last column of tiles overlaps the joint between the cement board and the greenboard if possible. Now, you can use either caulk or mesh tapes to close the gaps between the backer boards. Cut the board to measurements using a jig saw. Install the first full . For gaps larger than that, you'll need a good sealant. option 3: attach 6 inch wide waterproofing tape to the front of the cbu and drape it . In . Advice about gaps in cement boards. Where the tile overlaps the gap above the lip, you need to caulk where the tile hits the tub. I stopped using GreenEBoard two years back. Fasten the product with specified nails or screws (as listed in "Materials Put a surface bead of caulk over the filled gap. The tub has about a 1/2 - 3/4 in "ridge" on the three wall sides that the backer board is resting on. I don't tape corners. Determine layout of HardieBacker cement board. Once the sealant has dried, you can paint the surface with latex-based paint. What do you do with a gap between the tub and cement board? A lot of the jobs we do they don't bother to seal to the cement board and tub, they . Not only cement board (hardi is fine) but you must go 3-4 feet up. Leave a 1/8 gap between all panel edges. The next step is the thinset and taping. What do you do with a gap between tub and cement board? How to Install Cement Board on the Floor? there should be a small gap between the backer board and the tub 1. cement board off lip. 6. ANSWER - No there should not be a gap between the top of the bathtub flange and the backer board on the wall. ANSWER. You have to prepare the floor first with a trowel and putty knife to even the surface and spread the mortar properly. I never allow the cement board to rest on top of a bathtub edge. Place each individual tile evenly and apply pressure against the board and wall. Mix a small batch of thin-set mortar as directed by the manufacturer, mixing the dry powder with water in a bucket. Then just fill up the tub with water and silicone. Do not align HardieBacker cement board with plywood joints. Then they install the bottom tile so that it overlaps the gap. The cement board should be plumb, hence the need for shims sometimes. PROBLEM SOLVED for Tub Flange when Installing Cement Board and Tile. JW - Last edited by a moderator: Nov 26, 2016 johnfrwhipple BATHROOM DESIGN & BUILD Messages 3,225 Apply it to the wall with the bottom edge about 1/4 in. The backerboard is screwed into the studs with the mfg.recommended screws. The gap would not be the cause of water getting behind the tile. If there is a gap between the tub and the cement board, fill it with a sealant. If you have tile on the wall adjoining the tub, select a caulk that matches the color of the grout. When installing above a bath, leave at least a inch gap between the tub and cement board to prevent the wicking of moisture. Position the screws at least 1/2-inch, but no more than 2 inches, from the edge of the sheet. Secure Backer Board with Screws. Then apply a generous amount of thin-set to the bottom bathtub tile and . In these photos, I used Hydroban liquid waterproofing by Laticrete. Definitely use cement board instead of green board. Caulk the gap Ideally, you would leave a 1/8 inch gap which would then have the sealant applied to it. I do tape bevels simply to make a flush surface for the tiles. He also suggested "spackling" the joint (s) with thinset, not joint compound. If a space is smaller than 1/4 inch, apply a single bead of caulk to the edge. I suggest shimming the studs (only if you have to) to get the cement board down over the tub lip. Apply sealant to both sides of your tub-cement board joint, then smooth it out with a putty knife. Fill larger gaps with foam backer rod, sometimes called spline. Use minimum 1/2" exterior grade plywood or equivalent, positioned across the wood. Cover the bathtub with a drop cloth and tape the edges to the tub to make sure no dust or debris escapes into the tub beneath the cloth's edge. i used durock cement board as a base. Anyway, I'm ready to tape the joints but my question is this: Around the top and down one side of the tub surround there is about 1/4" gap between the cement board and the old drywall. Do not just cut a strip near your tub. Use 1/8 inch spacers to maintain the gap as you secure the board with the cement board screws. (For steel stud applications,use 1-1/4 DUROCK Brand Steel Screws.) There is approximately a 2" gap between the corner of the room and the bath tub. For tile backer boards such as Durock, Wonderboard, Hardiebacker, Permabase, and others the seams between the board need to be treated with 2-inch alkali-resistant mesh tape. above the tub. my intention was to make them as tight as possible being that i was going to fill them with mortar anyway. Hanging cement board is one job where gaps are desirable. Bruce geoffrey_b 5 years ago The tile is "supposed" to cover the gap. however.. Space the bottom sheets 1/4 in. What do you do with a gap between tub and cement board? Cut holes in the board for fixture placements. Attach the HardieBacker Cement Board with HydroDefense Technology. Then apply a generous amount of thin-set to the bottom bathtub tile and position it 1/8 in. silicone). Leave a 1/8-inch gap between each backer board sheet. Ensure cabinets are level and secure. It states no more than an 1/8" gap between the cement board and flange, and then says to seal the gap with caulk. There are a variety of sealants available, but a silicone-based sealant is the best option for this type of surface. (He hates it when I do projects.) cabinet. Measure the wall surface where the cement board will be placed to support the tiles. When installing the cement backer board, I like to leave a 1/8-inch gap between pieces. option 3: attach 6 inch wide waterproofing tape to the front of the cbu and drape it . Then apply a generous amount of thin-set to the bottom bathtub tile and position it 1/8 in. If you have a small gap (1/8 inch or less), a caulk can usually handle it. Cover an area just large enough for the first cement board sheet. The best approach when installing cement board or other tile backer around a tub is to keep the cement board out of the lip area. Leaving a gap between GreenEBoard and tub tile flange I like to leave about an 1/8" - 3/16" of a gap between the top of the tub's flange and the GreenEBoard. I suggest shimming the studs (only if you have to) to get the cement board down over the tub lip. gap between sheets of cement board. For a tub the absolute minimum is 3' up around the tub is either cement board or drywall with membrane or drywall plus cement board. Your local inspector might require higher. * with 1-1/2 hot-dipped galvanized roong nails spaced 8 o.c.for walls,6 o.c.for ceilings,or using 1-1/4 DUROCK BrandWood Screws with the same spacing. then redgard all the cbu. The tub flange can really be a pain in the butt when installing a tile tub surround. 1. This gap is then filled with pure silicone caulk before the ceramic tile is installed. The backerboard is screwed into the studs with the mfg.recommended screws. 1. He suggested filling in the gap with a strip of hardi-backer (easier to work with than cement board)--~3/4 wide. DH says the cement board should come over the flange, without touching the tub rim/ledge itself (maybe 1/4" space). Alkali-Resistant Mesh Tape. Use nails or screws as temporary spacers to create a 1/8-in. The tile should and does extend down close to the tub and then that gap is sealed with caulk. Technically, after the tile is installed over the backer board that gap between it and the tub ledge should be filled with an ASTM C920 sealant (caulking e.g. Provide a 1/4 in. Cement board used on walls typically is 1/2 inch thick, and so is the drywall you use in most rooms in the house. Apply enough mortar for single . Fasten board to wood studs spaced at 16 o.c. 1 I've about installed almost all the cement board for my bathroom tile renovation around the 3 sides of the tub. 1/4-inch Leave a 1/4-inch gap between the backer board and the wall. Fill gaps up to 1/4 inch in width with caulk. option 2: don't know if this is possible without removing all screws in cbu, but if possible, somehow pull the bottom of the cbu away from the studs and then put a 12 inch wide strip of 6mill poly behind the cbu and drape into pan. The cement board must be properly backed at tub edge to keep it stiff. The best approach when installing cement board or other tile backer around a tub is to keep the cement board out of the lip area. If your gap is smaller than 1/8 inch in width, use regular caulk; fill gaps larger than 1/8 inch with a sanded caulk. If you're installing the cement board yourself as part of a tiling project, the best way to bring the edges flush is to add shims to the wall studs before you hang it. The gap between it and the tub is grout filled. Allow slight gaps - approximately 1/8 inches - between cement boards to account for any expansion due to heat. Install the First Sheet. A better backer board is Wonder Board Lite. However, my husband would have thrown the whole mess in the tub and stomped on it if we hadn't made it fit a little easier. For the 2" gap that runs the depth of the tub, should I use cement board or dry wall? Although some say you should have weep holes along this gap so any water behind can weep out into the tub. above the lip of the tub. Once all the boards are nailed to the surface, fill the joints with a silicone-based caulk or taping . In the bathroom, however, water-resistant drywall is recommended, and this is often 5/8 inch thick. Allow a slight gap of approximately 1/8 inch between cement boards to account for expansion. Now, apply the tile in the small section that is sticky right now. Allow a inch gap between the boards and the tub for movement of the tub floor or walls due to temperature changes and settlement of the house. Should cement board go over tub flange? above the lip of the tub. The next step is the thinset and taping. Use 1/8-inch spacers to maintain the gap as you secure the board with the cement board screws. I use 1/8 inch gap and that give me more room for silicon on the corners. option 2: don't know if this is possible without removing all screws in cbu, but if possible, somehow pull the bottom of the cbu away from the studs and then put a 12 inch wide strip of 6mill poly behind the cbu and drape into pan.