Theory and practice

The required amount of jointing mortar depends, in principle, on the particular joint width and joint depth of the element surface that is to be grouted. For example, the joint width of natural-stone pavings is largely dependent on the dimension deviations of the paving block and the workmanship. The joint width values specified in the DIN 18318 for natural-stone pavements are usually not met and are rather considered as minimum joint width. As a consequence, significant increased mortar requirements for natural-stone pavings can arise out of that.

An unprofessional paved bond can be the cause of long-term damage. This also applies to slabbed surfaces, that do not have a sufficient adhesive bond from the paving blocks underneath to the bedding material. We recommend the application of our high-performance specialty mortar BM 04 or BM 04 S in combination with “Haftfix” as bond adhesive.

Important information

After the hammer setting of the elements, the remaining joint space shall be completely filled in with jointing mortar. For mosaic sett pavements the joint depth shall be at least 3 cm. Pre-filling of joints with mortar or any other joint fillings are not permissible.

The required amount of jointing mortar is calculated from the product of the joint volume and the specific consumption per volume unit (see line “consumption” in the particular tables “Technical Information”). In recent years the proportion of paving blocks resp. slabs of natural stone with undercut has been increasing. Thereby in parts, the foot area is significantly smaller than the surface area. This results in strongly conical joints which have a major influence on the utility values. Please contact us, if you have any questions or inquiries.

Please consider, that a faultless professional paving is necessary for the grouting of joints.

Dimension deviation

Example for dimension deviations of natural-stone paving blocks with split-rough surface.


Example for paving blocks with (too) strong undercut.

Natural stones

Example for natural-stone slabs with strong undercut.

1. As a result of the undercut, significantly wider joints in the lower joint area occur. As a consequence, a significant increased mortar requirement of jointing mortar arises out of that, compared to joints with constant width.


2. The joint depth is calculated from the block height minus the height that the bedding mortar rises up in the joint space during the setting of the blocks. The joint depth of slabbed surface is identic with the slab thickness.

Section through paved surface

The section through a paved surface shows that STEIN TEC® jointing mortars even fill up strong undercuts completely and bubble-free.

Section through paved surface

The bedding mortar rises up into the jointing space while hammering down the paving blocks.

We would like to point out that the terms “large pavement”, “small pavement”, and “mosaic sett pavement”, basing on the invalid DIN 18502, do not exist any longer. DIN EN 1342, which has replaced DIN 18502, only defines nominal dimensions for paving-block dimensions.