How to check tile and grout: lippage, coverage and joints

Tile is the trade where the best time to check the work is before it is finished. Once grout is in, a high edge, a hollow tile or a drifting joint is still there, but it is far more expensive to correct and far more obvious to the person standing in the room. This guide is for the tile contractor or crew lead checking a floor, wall or backsplash before grouting and again at handoff.

Start with the surface under the tile

Most tile problems that look like a setter’s mistake start in the substrate. A surface with dips and humps gives the tile nowhere flat to sit, and no amount of care in the setting material fully makes up for it. Lay a straightedge across the surface in several directions, and look along it with a light held low, so shadows show the low and high spots. How flat is flat enough depends on the tile size and the setting method, so the figure comes from the setting-material and tile manufacturers and from industry guidelines such as the TCNA Handbook and the ANSI A108 and A118 tile installation specifications. Read the current editions; this guide does not restate them.

Lippage: what it is and why it happens

Lippage is the difference in height between the edges of two neighboring tiles. A little is normal for some tile, which is why the allowable amount depends on the product and the joint, but a lip you can catch with a fingertip, or one that throws a shadow in raking light, is the kind a homeowner notices and complains about.

• The surface. A substrate that is not flat sends its error straight up through the tile.
• The tile. Warped or uneven tile, especially in larger formats, will not sit flat against its neighbor however it is set. Checking a few boxes before you start is cheaper than finding out on the wall.
• Coverage. Tile set on too little setting material sinks unevenly or rocks while the material cures.
• Leveling and cure. A leveling system only holds the tiles together while the material cures. If it is released early, or the floor is walked on too soon, tiles can settle apart.
• Rushing. Setting more area than the open time of the material allows leaves the tiles at the end of the batch set in material that has already begun to skin.

How to spot lippage

Get low and look across the surface with a light coming from the side. A continuous, clean line of reflection across the tile means the surface is reading flat. A jagged or broken band means edges are sitting at different heights. Then run a flat palm, or a fingertip, across the joints. Do this before the grout goes in, while a tile can still be lifted and reset.

Hollow spots and coverage

Full contact between the tile and the setting material matters because a tile that is partly unsupported cracks, loosens or sounds hollow under foot. Tap tiles lightly with the handle of a tool or a coin and listen for a change in sound. Hollow areas near edges and corners are worth checking first. On a large tile, lifting one while the material is still workable shows you the coverage underneath, and it is the quickest way to learn whether the troweling and back-buttering are doing their job. Large tiles raise the stakes, because a small hollow area under a big tile is a larger share of its support.

Layout and cuts

• Joint alignment. Sight along the joints in both directions. Drift that starts small at the first row is obvious by the far wall.
• Slivers. A narrow strip of tile at a wall or doorway looks like a mistake even when the room forced it. Check the layout before setting and move the starting line if you can.
• Cuts at the edges. Look at where cut tiles land at doors, outside corners, penetrations and around fixtures. Clean, consistent cuts and tight edges are what the eye reads as quality.

Movement joints and the perimeter

A field of rigid tile needs soft joints where it changes plane, at its perimeter, and at intervals in large areas. The check is whether they exist and whether they are filled with a flexible sealant instead of grout. The common misses are the inside corners of a shower, where a wall meets a floor, and the perimeter of a floor. How far apart they belong depends on the installation and the area, and comes from the installation method in the industry guidelines and the product instructions, not from this page.

Grout joints

• Consistent width. Joints that wander in width point back to layout or to tile that varies in size.
• Full joints. Look for pinholes, voids and low spots, especially along edges, where a joint can look filled and not be.
• Color. Patches of lighter or darker grout usually mean uneven water at mixing or cleaning, or an uneven cure.
• Haze and residue. A film left on the face of the tile is easier to remove early than late. Follow the grout manufacturer on cure time before sealing or using the area.

What to photograph

• The prepared surface, with a straightedge laid across it.
• The back of a tile you lifted to check coverage, if you did.
• The dry layout, before setting, where the starting line and the edge cuts are visible.
• The set tile before grout, photographed in raking light.
• Movement joints and the perimeter before they are closed.
• The finished grout, close up and from standing height.

A dated photo of the work before grout is what lets you answer a lippage or hollow-tile call with a record instead of a memory.

When to stop and ask a professional

Bring in someone qualified if you find cracking that follows a pattern, a floor that moves, signs of moisture where it should not be, or a question about the substrate that is outside your scope. A tile check is about catching your own misses while they are cheap, not about deciding a structural question.

Where Supervisr fits

If your crew photographs these stages, Supervisr reads each photo as it arrives and flags what looks off, such as tile edges that sit proud of their neighbors, inconsistent grout joints or areas that look unfinished, each with a plain-English reason and a next step, and files the rest to the job record. You can try the free photo check on the homepage with a photo from a recent job: three analyses, no signup, no card. Supervisr is an AI reading a photograph, it only sees what is visible in the frame, and it is not an inspection.

Questions contractors ask

Supervisr can make mistakes. Double-check responses, and use with caution.