Grouting granite slabs in the outdoor area

Unlike indoors, grouting granite slabs outdoors without mortar is recommended. Open joints made of grit or sand regulate the flow of water and avoid standing water on the surface. The granite slabs should, however, lie in the bed of gravel or sand.

Loose bed and open joints

Granite slabs in the outdoor area can be laid in mortar (€ 7.79 at Amazon *), gravel or sand bed. While grouting with grout (€ 38.80 at Amazon *) is recommended for a bed of mortar, unsealed joints are preferable for grit or sand. Joints filled with sand or fine grit support an even flow of water from the granite slabs. The slightly capillary effect slows down the water seeping through the joints and in this way prevents under- and rinsing out.

  • Also read - Laying granite slabs - even without joints
  • Also read - How to lay granite slabs on gravel
  • Also read - cut granite slabs yourself

Divided opinions on grouting

Companies that focus on the stone, such as granite factories, recommend completely "leaving the joints open" or filling them with sand. The joints should be 0.5 to one centimeter wide. This prevents the edges from flaking off in the long term.

Horticultural companies often advocate jointless butt joint installation in order to prevent weed growth. Grout manufacturers do not recommend open joints, as the risk of flushing out the joints and the bed of gravel or sand is very high.

Open grouting of granite slabs

  • Fine sand with zero to two millimeters
    Grain size or
  • Lime sand broken or
  • Diabase crushed sand
  • Quartz sand or
  • Basalt flour
  • water
  • broom
  • brush
  • Water hose or
  • Watering can
  • Vibrator

1. Sludge (except basalt flour)

Spread the sand in an even layer of about five millimeters on the granite slabs.

2. Filling the joints

Sweep the wet sand into the joints with a broom. Drag the joints with the brush and grasp again up to plate height.

3. Special case basalt flour

The basalt flour must be stored dry into the joints and to be stored.

4. Shake out

Shake the granite plates with a total area evenly.

5. Clean

Splash the plate surfaces with a strong water jet and remove sand residues completely.

6. Relapse

Repeat the frending after two to four weeks.

Tips & Tricks If you choose quartz and limestone sand, brillation are created after drying bright to white joints. Banquet sand dries out to a dark joint picture.