Grouting of Hairline Cracks

Chips Off the Old Block

and other ruminations about masonry by

Larry D. Jenks

Grouting of Hairline Cracks                                                                                          

If the mortar joints develop small “hairline” cracks, surface grouting may be an effective measure to fill them. The impact of surface grouting on masonry aesthetics should generally be considered before work begins, since the appearance of the mortar joints will change somewhat. A recommended grout mixture is 1 part portland cement, ⅓ part hydrated lime and 1⅓ parts fine sand. The joints to be grouted should be dampened. To ensure a good bond, the masonry units must absorb all surface water. Clean water is added to the dry ingredients to obtain a fluid consistency. The grout mixture should be applied to the joints with a stiff fiber brush to force the grout into the cracks. Two coats are usually required to effectively reduce moisture penetration. Tooling the joints after the grout application may help compact and force the grout into the cracks. The use of a template or masking tape may be effective in keeping the brick faces clean.