Repairing Loose Porcelain Patio Slabs with Priming Slurry

Step 1: Mark and Lift the Loose Slab

Loose porcelain slab (B), marked for orientation, is lifted off mortar bed (A) onto a bucket.

Watch this step (1:42)

Parts in this step: (A) mortar bed, (B) porcelain slab

You'll need: Chalk, Vacuum suction lifter, Buckets

1. 1.1 Mark slab orientation with chalk
   • Chalk two alignment lines across the joint between porcelain slab (B) and a fixed neighbor.
   • Mark both sides of the joint to return the square slab in the same orientation.
   • Keep chalk marks visible: rotating the slab makes it rock on mortar bed (A) contours.
2. 1.2 Lift the loose slab with a vacuum suction lifter
   • Center the vacuum suction lifter on the dry top face of porcelain slab (B).
   • Engage the vacuum pump until the pad seals against the tile.
   • Lift the slab straight off mortar bed (A) with proper posture.
   • Set the slab face-down on an overturned bucket at working height.

• Tip: Mark both joint sides before lifting a square slab to match the edge.
• Tip: Rest the lifted slab on an overturned bucket off the ground for grinding.
• Heads up: Use a vacuum suction lifter and proper lifting posture to avoid pinched fingers or back strain.

Before you move on: Chalk marks are clear on both slabs, and the mortar bed is solid, not crumbling.

Step 2: Clean the Mortar Bed and Grind the Slab Back

Mortar bed (A) is scraped clean, and the back of porcelain slab (B) is ground flat and brushed dust-free.

Watch this step (2:14)

Parts in this step: (A) mortar bed, (B) porcelain slab

You'll need: Notched trowel, Buckets, Disc cutter, Hand brush

1. 2.1 Scrape loose debris off the mortar bed
   • Drag the notched trowel's flat edge across exposed mortar bed (A).
   • Scrape off flaky dried cement, loose sand, and ant soil.
   • Clear the recess so fresh slurry bonds to solid mortar.
2. 2.2 Grind high spots flat on the back of the slab
   • Check the back of porcelain slab (B) on the bucket for old primer ridges.
   • Wear eye, hearing, and dust protective equipment and safety footwear.
   • Grind old mortar high spots off the slab back with the flat disc cutter blade.
   • Grind ridges flush so the new primer coat cannot push the slab above adjacent tiles.
3. 2.3 Brush grinding dust off the slab back
   • Sweep the ground back of porcelain slab (B) with the hand brush.
   • Remove loose grinding dust and grit to the edges; dust blocks primer adhesion.

• Tip: Grind down cured mortar ridges so new slurry does not raise the slab.
• Tip: Sweep off grinding dust before priming so the new slurry bonds to the porcelain.
• Heads up: Wear eye, hearing, respiratory protective equipment and safety footwear with the disc cutter.

Before you move on: High ridges on the slab back are ground flat and both surfaces are dust-free.

Step 3: Apply Priming Slurry to the Slab and Bed

The porcelain slab (B) back and mortar bed (A) have a 1 to 2 mm priming slurry coat.

Watch this step (3:09)

Parts in this step: (A) mortar bed, (B) porcelain slab

You'll need: Paddle mixer, Buckets, Pointing trowel, Priming slurry

1. 3.1 Trowel priming slurry onto the back of the slab
   • Mix priming slurry in a bucket with the paddle mixer to a thick, flowable paste.
   • Scoop priming slurry onto the porcelain slab (B) back with the pointing trowel.
   • Spread an even 1 to 2 mm coat across the whole back face.
   • Trowel slurry to all four edges, leaving no unprimed border.
2. 3.2 Pour and spread priming slurry over the mortar bed
   • Pour priming slurry from the bucket onto the scraped mortar bed (A).
   • Spread a generous 1 to 2 mm coat over the recess with the pointing trowel.
   • Fill shallow bed voids so both primed faces meet without hollow spots.

Key measurements

• Priming slurry coat thickness: 1 to 2 mm on slab back and mortar bed
• Priming slurry tub weight: 17 kg

• Tip: Trowel a 1 to 2 mm layer instead of brushing or rolling a thin, watery coat.
• Tip: Cover the slab back to the edges for full perimeter support.
• Heads up: Do not thin the slurry or leave a 1 to 2 inch unprimed border, or the slab will wobble.

Before you move on: Slab back and mortar bed have a 1 to 2 mm slurry coat to every edge.

Step 4: Re-lay the Slab and Rinse the Joints

Porcelain slab (B) sits flush on mortar bed (A) in its original orientation, with excess slurry rinsed off.

Watch this step (3:45)

Parts in this step: (A) mortar bed, (B) porcelain slab

You'll need: Vacuum suction lifter, Garden hose, Priming slurry

1. 4.1 Lower and work the slab into position
   • Attach the vacuum suction lifter to the primed porcelain slab (B) face.
   • Align the slab chalk marks with those on the adjacent patio tile.
   • Lower the slab onto the primed mortar bed (A) in its original orientation.
   • Press and slide the slab back and forth to expel air and seat it flush.
2. 4.2 Rinse excess slurry from the surface and joints
   • Release and remove the vacuum suction lifter from porcelain slab (B).
   • Immediately spray the slab face and joints with the garden hose.
   • Rinse squeezed-out priming slurry from the joints before it cures and stains the tile.

• Tip: Rub and slide the slab while pressing down to settle it flush with neighboring tiles.
• Heads up: Wash excess priming slurry off the porcelain face and joints immediately before it dries.

Before you move on: Chalk marks align across the joint, the slab sits flush with adjacent tiles, and no wet slurry remains on top.