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Mixing mortar for beds, laying and grout

Mortar is cement and sand — no gravel. The same bag is mixed to different consistencies for bedding, laying and grout; the joint decides how wet it should be.

Last reviewed Oct 23, 2026

The bag or tube wins

Product formulations change. If the manufacturer’s printed ratio, temperature or cure differs from this page, follow the manufacturer — and tell us so we can update the guide.

At a glance

By job

Block bedding (about 3/8 in joints)

Ratio
1 × 80 lb bag
Water
2.5–3 qt
Mixing
3–5 min, rest 5, remix
Working time
1–1.5 h
Cure
24 h before load

Full bed, not spot dabs; check level after every block.

Stone or paver bedding

Ratio
1 × 80 lb bag
Water
A little less — stiff and damp
Mixing
3–5 min, rest 5
Working time
45–60 min
Cure
Foot traffic 24 h

It should hold a trowel ridge; back-butter each piece — spread mortar on its back — so no hollow spots remain.

Joint grout

Ratio
1 part mortar : 2 parts sand
Water
Wetter than bedding
Mixing
3–5 min
Working time
20–30 min
Cure
Keep damp 24 h

Work it while the bed is still alive; strike flush and wipe haze as you go.

Choose the product

  • Use a preblended Type N or Type S mortar mix. Type S is the stronger exterior choice; Type N is general-purpose.
  • Use a proprietary joint grout where one is sold for your pavers or stone. If mixing your own, the step’s “1:2 mortar grout” means 1 part mortar mix to 2 parts sand by volume.
  • Never use concrete mix as mortar, or mortar as concrete.
  • For thin veneer or tile, use the adhesive the manufacturer specifies — not mortar.

Mix it

  1. Water first, then powder. Mix 3–5 minutes until uniform.
  2. Let it rest 5 minutes, then remix without adding water — the rest lets the mix reach its real consistency.
  3. Bedding: stiff enough to hold a ridge when you drag a trowel through it. Grout: flows off the trowel but does not run.
  4. Mix small batches; mortar stiffens without warning, and adding water later weakens it.

Weather window

Temperature

40–90°F (5–32°C)

Rain

No rain or freezing for 24 hours. Cover fresh work.

Watch for

  • Shade the work in heat and mist joints through the first day.
  • Do not mix or lay on frozen ground; the mortar will not bond.

Cure

  • Foot traffic after 24 hours; furniture after 72 hours.
  • Joints finish curing through the first week; mist them once a day in a heat wave.
  • Keep rain off for the first day — fresh mortar washes out.

When it goes wrong

  • Crumbly joints

    Likely cause: Mix too dry, or it dried too fast in sun and wind.

    Fix: Mix to the right consistency; shade and mist the first day.

  • Hollow-sounding stone

    Likely cause: Dry spots under the piece, or the mortar skinned over before setting.

    Fix: Back-butter each piece (mortar on its back) and set it with a slight twist while the bed is alive.

  • Mortar haze on the faces

    Likely cause: Wiping too late, after the film cured.

    Fix: Wipe as you go with a damp sponge; never let a film dry on porous stone.

Safety

  • Wear gloves and eye protection; wet mortar is alkaline and can burn skin.
  • Wear an N95 when handling dry mix — silica dust.
  • Keep wash water out of storm drains.

Sources