Stone Retaining Walls – Tuckpoint Them to Preserve Them
What are the common problems – An old stone retaining wall that was well constructed can last hundreds of years… no kidding. Even the best built walls though will eventually succumb to the powers of Mother Nature and will at some point need some type of repair. Generally that repair is the re-setting of a few loose stones and the replacement of missing or deteriorated mortar joints.
Pressure wash to remove dirt and loose material – The first step in the tuckpointing process is to thoroughly pressure wash the wall. This not only removes dirt, mold and soot but the pressurized water will etch the surface of the joints which will aid in the bonding of the replacement pointing mortar.
Care should be taken not to get to close to the wall. It may take a few minutes to figure out the distance needed to get the best cleaning action without destroying the wall itself!
Fill in all mortar joints if you can – Whenever I have a stone tuckpointing job I always try to convince the customer to completely point in all the mortar joints. There are three reasons for this.
The first reason is that most walls have a rake joint so it is easy to point in over the existing mortar.
The second reason is that the color of all the new pointing mortar will be the same since all the joints will be tuckpointed. This prevents problems when the customer is expecting the new joints to match the old joints perfectly; something everyone wants but most are not willing to pay for.
The third reason is that you can use a grout back to fill in the joints which allows for quicker installation time and more value for the dollar spent, so the customer gets more bang for his dollars.
Mixing of the tuckpointing mortars – Since I typically use a grout bag I mix my mortar fairly loose or wet. I also use a bonding agent which will help initially with water dispersion throughout the mix but will become problematic on hot days due to the drying of the mortar in the grout bag.
So good advice is to keep the mortar loose and periodically clean and dampen your grout bag to remove any hardened material. This will allow you to apply even pressure as you grout the joints to a consistent thickness and make the application simpler and easier.
Squeezing the mortar into place – How to place the tuckpointing mortar can be done in numerous ways but the grout bag is the most productive. I start at one end of the wall and begin filling all of the deep holes in the wall with new mortar making sure it is about the same height as the existing mortar joints.
When I have finished with the deep holes I go back to the beginning and start grouting every joint. I let the new mortar stand ‘proud’ and ‘ride high’ above the face of the existing stone. This allows ample material when I push the mortar back into the joint.
Finishing the tuckpointing – After I have grouted a sufficient area I take a fat tuckpointer of ¾” or larger, depending on the joint size and start to push the mortar into the joint between the stones. This tightens the joint and closes off any voids that may have been missed during the grouting process.
Immediately after I take my tooling iron and ‘finish the joint out’ with the desired joint type such as flat, beaded or grapevine finish. Then when a light crust has formed over the new joints I take a soft brush and brush away any loose tags and smooth the joints out.
As with all masonry repairs the process isn’t too difficult however if you want your work to be presentable and to look nice, you must pay attention to the details!