Joint mortar can become sandy due to incorrect mixing

In almost all cases, a grout that becomes sandy will begin to show serious damage. In the case of lime and clay mortar, sanding indicates that the moisture balance in the masonry or in the ground has been "knocked out of joint". Cement mortar was not mixed properly or set too fast.

Causes of sandy grout

Sandy grout is often a first and good indication of substantial problems in old and existing buildings. Physically, mortar consists of binders, sand and water. During setting and drying, the water escapes and forms the hard joint filling.

Several causes can lead to a later sanding of the joint mortar:

  • The ratio of binder to sand is not correct
  • The width and depth of the joints is not "borne" by hard mortar
  • The burden of masonry presses and presses too much on the mortar stability
  • Temperature fluctuations lead to cracks in the mortar
  • Moisture and salts decompose the mortar
  • The processing temperature was too high and the mortar set too fast
  • The mortar had too little water
  • Air, room and wall moisture have affected the setting process

Lime and clay mortar

In old buildings, joints are filled with water-soluble lime and loam mortar. If the soil and / or wall moisture changes significantly, the binders dissolve. The masonry and the walls have a coherent "breathing behavior". If the stones do not allow enough evaporation, the moisture seeks the lesser path of resistance. The wetness concentrates and increases in the joints.

When refurbishing old mortar must be replaced with new mortar. When removing the old joint, a depth of at least three centimeters must be exposed. The new mortar must have a similar "breathability" as the masonry and the old mortar.

mixing ratio

When joint grout is mixed, building physics parameters should be taken into account when calculating the proportions of water, sand and binder. Wall drying must be done before processing.

Very careful when overfilling old joint mortar must be proceeded. Absence is eliminated as a symptom, but the cause continues to work and in turn seeks the simplest way. If the joints are incorrectly closed, the masonry can begin to become sandy.

Tips & Tricks

You can also use the technique of sacrificial and restoration plasters in joints to help with the drying out of masonry.

Artikelbild: RIDTHISING / Shutterstock

Video Board: How to Mix small amount of Sand Cement Mortar by hand