Grout Falling Out: Why Grout Comes Loose and Pulls Away From Tile

Grout falls out when it never had enough depth or grip, or when something keeps working it loose. The most common causes are shallow joints packed with thinset, dusty or wet joints that prevented bonding, shrinkage that left a gap at the tile edge, and tile or floor movement. Tap the surrounding tiles: if they sound hollow, the tile is the real problem and regrouting alone will not last.

The three ways grout comes loose

"Grout falling out" covers several distinct failures, and they point to different causes:

• Edge separation. A hairline gap opens between the grout and one or both tile edges. The grout itself is intact and may rattle or lift as a strip.
• Chunks or strips popping out. Sections of joint come out whole, often thin, leaving a shallow trench or exposed thinset.
• Erosion and crumbling. Grout wears away, turns powdery, or washes out a little at a time. This is usually weak grout rather than a bond or depth failure, and is covered in soft or crumbling grout.

This page covers the first two. If the joints are intact but simply low, see low or recessed grout joints; if cracks are the main symptom, start with why grout cracks.

How to tell the causes apart

The hollow tile tap test

The tap test is the single most useful check for loose grout. Take a coin, the back of a key, the plastic handle of a screwdriver, or roll a golf ball across the floor. Tap or drag across the center and each corner of every tile surrounding the loose grout. Well-bonded tile gives a sharp, solid click. A tile with voids or a failed bond gives a hollow, drum-like knock that is clearly different once you hear both. Mark hollow tiles with painter's tape.

A small hollow spot at one corner of a large tile is common and not always a problem. A tile that sounds hollow across most of its face, or that moves when you press a heel on one edge, is unbonded and will keep breaking the grout around it.

Inspect the piece that fell out

Measure the thickness of a loose piece against the tile thickness. Look at the sides that were touching the tile: grout that bonded properly usually leaves a rough, slightly torn face and some residue on the tile edge. A piece with smooth sides and a clean tile edge never bonded. A piece with a flat, gray bottom sitting on hard thinset was too shallow.

Causes ranked by likelihood

1. Shallow grout over thinset in the joints

This is the most common cause of grout coming out in strips. When tile is set, thinset squeezes up into the joints. If it is not cleaned out before it hardens, the joint ends up only partly open, and the grout becomes a thin cap. Industry practice, reflected in ANSI installation standards, is that joints should be free of setting material to at least two-thirds of the tile thickness so the grout has enough body and side contact to stay put. A 3/8 inch tile should have roughly 1/4 inch or more of open joint. The background is on grout joint depth and anatomy of a grout joint.

Thin tiles such as mosaics and some glass are a special case: with 1/4 inch or thinner tile, even small thinset squeeze-out leaves very little depth.

2. Dirty, dusty or contaminated joints

Grout bonds to clean, slightly damp tile edges and mortar. Dust from cutting, grout dust left after raking out old grout, a film of thinset haze on the edges, or a sealer or grout release that ran into the joints all act as bond breakers. This is especially common in repairs: someone rakes out old grout and packs new grout into joints full of fine dust. The result is grout that looks fine for a few weeks and then lifts out as a clean strip.

Very dense porcelain, glazed tile edges, and glass also offer less grip. Polymer-modified or high-performance grouts (ANSI A118.7) and epoxy grouts generally bond better to these edges than basic unmodified cement grout.

3. Shrinkage away from the tile edge

Cement grout shrinks as excess water evaporates. In a well-filled joint that shrinkage is small and spreads out. When the grout was mixed too wet, overly sponged, or used in joints wider than its rated range, it pulls back from one tile edge and leaves a hairline gap. Water and dirt then work into the gap, and over months, traffic levers the strip loose. The mechanism is explained in why grout shrinks.

4. Tile or floor movement

Hollow tiles that rock under load, a floor that deflects, or a tile field pressing against walls with no perimeter joint will grind grout loose over time. Look for the pattern: loose grout concentrated around particular tiles, in the middle of a span, or along walls and thresholds. Recurring problems of this kind are covered in grout keeps cracking, and joints that should be sealant are explained in caulk vs grout for movement joints.

5. Failed bond from poor packing or early stress

Grout that was skimmed across the surface instead of forced in with the float at an angle often leaves voids below the face. The surface layer then breaks through. Grout that was walked on, scrubbed hard, or flooded with water before it gained strength can also lose its grip. Proper packing technique is covered in grout float technique and the science in grout compaction and joint filling. Hidden voids that show up as small holes are a separate symptom: see grout pinholes and voids.

Fix summary

For a few joints, follow spot grout repair. For larger areas, use how to remove grout and how to regrout tile. Matching the new color to the surrounding joints is covered in matching existing grout color.

Prevention

• Clean thinset out of the joints while setting, before it hardens. A margin trowel, a joint-cleaning tool, or a toothbrush handles squeeze-out easily in the first hour.
• Vacuum joints just before grouting and remove any cutting dust.
• Keep sealers, impregnators and grout release off the joint edges unless the TDS says otherwise.
• Force grout in diagonally with the float in two directions; pack, do not skim.
• Measure water and avoid over-sponging (see grout sponge technique).
• Check tile coverage during setting by pulling a tile now and then.
• Leave perimeter and change-of-plane joints for sealant.