Cracked Grout on Your Terrace Tiles? Regrout or Re-Waterproof?

The terrace is tiled, the tiles look fine, but the lines between them have cracked and gone dark with moss. Meanwhile there is a stain growing on the ceiling below. The obvious move is to rake out the joints and fill them again. Sometimes that is exactly right. Often it is the cheapest way to repeat the same leak.

The question is simple: is the water getting in through the joints only, or has the waterproofing layer under the tiles given up?

What tile joints do and do not do

On most Bangalore terraces the tiles are a finish laid over a screed, and the waterproofing sits below or within that build-up. Grout fills the gap between tiles and keeps dirt out. It is not the waterproofing layer. Water that enters a cracked joint is meant to be stopped by the membrane beneath. If the membrane is sound, a cracked joint is a maintenance item. If the membrane has failed, a cracked joint is just the doorway.

A ten-minute check

1. Look at the ceiling timing. Does the stain below grow within a day or two of heavy rain? That points to water entering from above. A stain that stays the same through dry weeks suggests an old leak, or a different source.
2. Tap the tiles. Use a coin or the handle of a screwdriver. A dull, hollow sound means the tile is no longer bonded to the screed, which usually means water has been getting underneath for a while.
3. Check the edges. Tiles lifting or tilted near the parapet, near drain outlets or along expansion gaps are a sign that moisture is moving underneath.
4. Look at the slope. After rain, does water pool in patches? Standing water gives cracked joints more time to leak. Read about blocked terrace drains.
5. Note the age of the last repair. If joints were filled before and cracked again within a season or two, filling them again is unlikely to last.

When regrouting alone is reasonable

• The ceiling below is dry, and the cracks are only in the joints.
• Tiles are firmly bonded when tapped.
• Water drains off the terrace without pooling.
• The waterproofing is relatively recent and has been inspected.

In that case the joints are raked out to a clean depth, dust is removed, and they are refilled with a flexible, water-resistant material rather than plain cement paste. Plain cement grout is rigid, and it cracks again as the slab moves with heat and cooling.

When you need more than new grout

• The ceiling below is stained or damp and the stain follows the rain.
• A significant area of tiles sounds hollow or is lifting.
• The same joints have been filled before and have cracked again.
• The terrace has been waterproofed for many years and the system's condition is unknown.

Here the tiles in the affected area may need to be lifted so the screed and membrane can be inspected, repaired or replaced, and the surface relaid with proper slope to the outlets. It is more work than regrouting, which is why it is worth confirming the cause first. For a breakdown of what affects the price, see our guide to terrace waterproofing cost, and for why repairs fail, why waterproofing fails again.

What not to do

• Do not cover the whole terrace with a coating without checking the tiles. Paint-on products need a clean, dry, sound surface. Over loose tiles they trap moisture.
• Do not fill joints with plain cement and call it waterproofing. It is the shortest fix and the shortest lifespan.
• Do not work during or just after rain. Joint fillers and coatings need a dry surface to bond.

Where else the water could be entering

If the joints and tiles check out, look at the edges. A gap at the base of the parapet is a common source, covered in our guide to the parapet wall leak. If you plan rooftop solar, see terrace waterproofing before solar panels, because fixing a membrane under a panel structure is harder.

Where LoklFix fits

We check whether the leak is entering through the joints, the tiles, the edges or the membrane before recommending anything. If regrouting is enough, we will say so and not sell you a full redo.

Frequently asked questions