I finally got my materials right and found some time to work on tuckpointing the brick for the wing walls in the old back stairs. I’m thinking of this as a practice opportunity because the whole area will be covered behind lattice and clematis vine eventually. Although it won’t be very visible, I hope that by filling in the large mortar gaps I can reduce water infiltration along the tuckunder garage foundation where there is some evidence of damage.
From what I can tell, the old bricks on the house are pretty soft inside. I have read that modern cement-based mortar can really tear up old bricks like these because when stress is applied, the bricks break or crumble before the concrete yields. To address this issue, I made a lime-based mortar which should remain softer than the bricks. Because of the extended calcification process of lime, this mortar is also supposed to self-repair small cracks in it over time– a nice feature.
- 1 part hydrated lime (easier to find and work with than quicklime)
- 3 parts all-purpose sand (sharper than play sand)
- mortar colorant (optional– I used some left by the previous owners)
Add the dry ingredients to the water and mix until uniform. Wait five minutes, then mix again adding water or sand to reach the desired consistency.
For my project, I started with a wetter consistency so that the mortar would more easily flow into the deep crevices where the wall has sunken. I also sprayed all the bricks with water to help extend the curing time for the new mortar. For the wide gaps, I made a small trough out of some sheet aluminum and forced the mortar into the gaps with my square trowel.
For the places where the bricks hadn’t moved, I filled in the gaps in the mortar using a 3/8″ tuckpointing trowel taking mortar off a hawk. For this application, I experimented with a dryer mortar consistency and also with increasing the lime content. With too much water, the mortar just slid off the trowel. With too much lime, the mortar got overly sticky and more difficult to spread. With the rich lime mixture, I noticed the mortar making a cool sizzling sound while it sat on the hawk. I assume this was the lime cooking, though I didn’t notice any additional heat.
After working at it for a couple hours I had used up a gallon pail of mortar and was ready to call it quits. (I covered more than the just the area seen in the picture above.) The results are far from professional, but I don’t think they look too bad for a first effort. To continue to keep the mortar from setting too quickly, I lightly sprayed water over the new mortar every couple hours for the next day or so. For some of the deep cracks, I intentionally left the mortar shallow, so that I can finish with a second layer once the first has dried.