A reader recently wrote in and asked the following question:
I am looking for an alternative to "toothing out" a wall when building a wall on an existing wall.
I am a bit worried because our builder initially said that he was going to tooth out the existing wall when building the two adjoining walls from the room we are building on - but he then asked us to buy 30cm steel rods which he put into the wall by means of a drill on every third level. He called it something of a "crocodile". Would this be correct and is there a specific place he should drill into the wall as he just drills and inserts?
Les Abbott, expert Architect, provided the following answer:
To answer your reader's question. I am making a few assumptions regarding what she is talking about but "toothing" is a common practice when joining a new brick wall to an old one. The difficulty often is, however, that the old bricks can be very hard and it takes a lot of time and effort (that the builder may not want to spend) to chip out every third or fourth brick in order to build the new ones in, or it can be very soft which poses a different kind of problem. The whole idea is that a method needs to be used that will give a secure bond between the new and the old brick walls. I would generally have no difficulty with drilling and inserting rebar into the wall as a bonding mechanism. I would only make sure that the correct chemical anchor or approved epoxy adhesive be used to secure the bar in place in the existing brickwork. If this is done properly then there should not be any problem.
I hope that this answers her question. If she wishes to e-mail a photograph of the wall to me, I can confirm the issue with her directly.
L A Design Studio
You can find more articles by Les Abbott of L A Design Studio here.