How to Install Grab Bars on Tile Without a Stud Behind It

Why this matters

A grab bar is the one piece of bathroom hardware designed to be trusted with a falling person's whole weight, and it gets installed, more often than any other, into a finished tile wall with nothing solid where the person needs it. The bar that spins or pulls out does so at the exact moment someone is relying on it, and the injury that follows is worse than if no bar had been there, because the person committed their weight to it. This HowTo covers the case the Handyman grab-bar SOP flags as a stop: the right place for the bar has tile on it and no stud behind it. The load rule itself, and the arithmetic of why a flange screw in board fails, belong to the owner card and the SOP. See related: Grab-Bar Backing and Load: The Structural Rule; Grab Bar and Handrail Installation.

Before you drill

Find what is in the wall. The wall behind a tub or shower may hold the supply risers above the valve, a drain vent, and on an exterior wall or a wall shared with a room, electrical cable. Drilling into a pressurized supply line behind finished tile floods the wall cavity before you see a drop. Locate the valve and assume the risers run straight up and down from it until you have seen otherwise, from an access panel or the room behind.

Tile and backer board make silica dust when drilled. Ceramic, porcelain, stone and cement board all contain crystalline silica. Drill with water at the bit or with a drill fitted with a dust collection system and filter, following the controls for handheld drills in 29 CFR 1926.1153, Table 1, and use respiratory protection under a written program per 29 CFR 1910.134 wherever those controls are not in place.

Old tile may sit on an adhesive of unknown content. In houses from before the 1980s, black or dark brown mastic behind tile may contain asbestos. A few drill holes through tile into a mortar bed are a small disturbance; cutting or scraping out a section of tile and mastic to reach the wall is not. Do not open tile on a wall of that age until a sample has been tested.

The steps

1. Agree the position with the person first, standing where they use it. The 2010 ADA Standards for Accessible Design, a reference and not a requirement in a private home, place a horizontal bar with the top of the gripping surface 33 to 36 inches above the floor (609.4), with a 1-1/4 to 2 inch diameter (609.2.1) and 1-1/2 inches clear between bar and wall (609.3). Have the person stand or sit where they will reach for it, mark where their hand goes, and mark the bar at the height they choose inside that range unless there is a reason to leave it. Skip it and you will fix the structural problem at a position nobody uses.

2. Find the framing, and do not trust a stud finder through tile. Electronic finders read poorly through tile and a mortar bed. Better evidence, in order of reliability: the room on the other side of the wall (a closet or a bedroom where a finder works on drywall, or an outlet box that is fixed to a stud); a strong magnet run along the tile to find the screws that hold cement board to studs; measurement from a known stud at a corner or a door jamb, usually at 16 inches on center; and a small probe hole through a grout joint. Skip it and you drill flange holes into a cavity that turns out to be hollow, and now have holes to seal as well as no framing.

3. Try to land both flanges on framing before doing anything else. Bars come in lengths. On 16-inch framing, a bar whose flange centers fall 16 or 32 inches apart can often land on two studs at a position the person accepts. An angled or vertical bar may land on one stud where a horizontal one cannot. Skip it and you open walls or rely on anchors when moving the bar a few inches would have put it on wood.

4. If framing will not do, choose between opening the wall from behind and a listed anchor. The two are not equal, and the order is:

• Open from behind where the other side is drywall in a closet, hallway or bedroom. Cut an opening between the studs, install solid blocking (2x lumber screwed into both studs at the flange height, or plywood across several bays), and patch. This puts real wood behind the tile and is the strongest result. Before cutting, check the cavity with a non-contact voltage tester and cut no deeper than the drywall.
• A listed anchor rated for the substrate where the other side is also finished tile, a tub surround, or an exterior wall. Read the anchor's listing conditions, not its headline rating: the tested assembly has to match the wall you measured in board type and thickness, tile over cement board is not tile over gypsum board, and two layers of board are not one. If no listed condition matches, the anchor is not qualified here, and the job goes back to blocking from behind or to opening the tile.

Skip the listing check and the anchor's package figure becomes your design load in a wall it was never tested in.

5. Drill the tile without cracking it. Put painter's tape over the mark so the bit does not walk. For porcelain or stone, use a diamond core bit with water, starting at a slight angle to cut a crescent and then bringing the drill square; for softer ceramic, a carbide tile bit. Keep the drill's hammer function off through the tile, at moderate speed, with light pressure and water or a pause to keep the bit cool. Once through the tile, switch to the bit the fastener or anchor calls for to go through the backer board. Skip the care and a cracked tile under a flange becomes a water path and a loose flange.

6. Seal every hole before the screw goes in. Fill each hole with a 100 percent silicone sealant or the anchor maker's specified sealant, and run a bead around the back of the flange where the instructions call for it. Water that gets behind a flange runs down inside the wall to the sill plate. Skip it and the bar outlasts the framing.

7. Fasten to the instructions. Screws into blocking are long enough to engage the wood by the length the bar maker calls for, usually stainless or corrosion-resistant. Anchors are set and torqued to their own instructions. Do not over-torque on tile: a cracked tile under the flange takes away the bearing the flange needs.

8. Load-test by hand, and record what the test means. Pull out and push down on the bar hard, at each end and the middle, with your body weight braced, not hanging from it. There should be no movement, no click and no crack. A hand test confirms the fasteners found something solid; it does not certify the 250 pound-force design load the ADA Standards use (609.8), and the ticket should say exactly that. See related: Grab-Bar Backing and Load: The Structural Rule.

Worked example: two bars, two different answers

The customer is 81 and steps into a tub-shower facing the valve wall. She asks for a horizontal bar on the long back wall and a vertical bar at the entry, on the end wall opposite the valve. The tub is 60 inches long. The walls are tile, and the house is from the early 1990s.

Before drilling. The valve is on the end wall at the faucet end; the access panel on the far side of that wall shows the risers running straight up from it and nothing else in that bay. The back wall is shared with a bedroom closet, drywall on the closet side. The entry end wall backs onto a hallway, also drywall, painted. The mastic question does not arise: the tile is set on cement board, visible at the access panel edge, and the house postdates the era of concern.

Back wall bar. In the closet, a stud finder on drywall locates studs at 15-1/2 and 31-1/2 inches from the valve-wall corner, and a magnet on the tile confirms board screws on the same lines. She marks her reach at about 24 inches from the corner. A bar with flange centers 16 inches apart, centered on her mark, would want flanges at 16 and 32 inches; the studs are at 15-1/2 and 31-1/2, and moving the bar half an inch toward the corner puts both flanges on studs with her hand still on the bar where she wants it. Height: she chooses 34 inches to the top of the gripping surface. No anchor and no opening needed. That is step 3 doing its job.

Entry bar. The vertical bar wants to sit 4 inches in from the tub edge, where she steps over. The nearest stud on the end wall is 9 inches from the tub edge, so the bar cannot land on it at the position that helps her. The tech checks the anchor the shop stocks: its listed conditions are tile over 1/2-inch cement board, and the wall is tile over 1/2-inch cement board, so it qualifies. But the hallway side is plain drywall, and blocking from behind is the stronger result. The customer agrees to a patch and paint in the hallway. The tech checks the hallway cavity with a non-contact tester, cuts an opening in the drywall between the two studs either side of the bar location, tall enough to reach both flange heights, screws a 2x6 block across the bay at each flange height, photographs the blocking with a tape in the frame for the file, and patches. From the tub side he drills the tile with a diamond core bit and water, drills the cement board, seals each hole with silicone, and drives stainless screws into the block.

Tests. Both bars pulled out and pushed down at each end and the middle with no movement or sound. The ticket reads: "Back bar on studs at 15-1/2 and 31-1/2 in, top 34 in AFF. Entry bar on 2x6 blocking installed from hallway, patched. Hand-tested for engagement; not a certification of the 250 lbf design load."

How to verify you got this right

Run water at the bar for a minute with the shower and check the flanges and the tile around them for any path in. Look for a hairline crack radiating from any flange hole, which means the tile is cracked under the flange and the job is not finished. Then have the customer use each bar the way she will, stepping in and out once while you stand by, and ask whether the position is right. A structurally perfect bar in the wrong spot will not be used.

References

• 2010 ADA Standards for Accessible Design, section 609 (609.2.1 diameter, 609.3 clearance, 609.4 position, 609.8 structural strength), used as a reference and design basis; not binding in a private home.
• 29 CFR 1926.1153, Table 1, for silica controls when drilling tile and cement board, and 29 CFR 1910.134 for respirator use.
• The anchor manufacturer's listing and installation instructions, for the tested substrate assembly and rated load.
• See related: Grab Bar and Handrail Installation; Grab-Bar Backing and Load: The Structural Rule; The Grab Bar That Pulled Out of the Wall.