We do a lot of repairs to brick homes built before 1900. These buildings are built very differently than modern homes.
Most significantly, the walls in one of these old homes are structural masonry, not veneer masonry.
Very important distinction.
Structural masonry is any masonry that is carrying the weight of the building or some part of the building more than its own weight.
Structural masonry walls carry the weight of the floors and the roof in addition to their own weight.
Structural masonry walls in a typical brick home built before 1900 start below the basement floor and go straight up to the roof. Usually they’re 12″ thick in the basement, and then are 8″ thick up to the roof. The floor joists are notched into this wall. The roof rafters sit on top of the wall.
These walls are carrying the entire weight of the building, plus its occupants and their things, plus any snow that may be sitting on the roof. This weight is transferred downward as pressure on the soil or rock where the house is built.
Veneer masonry is used in newer homes and is usually built on the outside of a house after everything else is built. This brick “skin” carries no weight other than its own.
In these homes with veneer masonry siding, there is usually a structural masonry foundation (8-12″ thick concrete block), which forms the basement. Floor joists are laid across the foundation, 2×4 walls form the outside structure, and this wooden structure carries the weight of the upper floors and the roof.
The brick is laid up as a veneer over the frame walls. It’s a 2 layer system where the masonry is used as siding, but is not carrying the weight of the building. Usually the veneer is 4″ thick in the case of brick, or 1.5″ thick in the case of fake stone or thin brick veneer.
So in the old homes, the brick is 8″ thick from the ground up to the roof, and carries all the weight.
In newer homes (post 1945, generally), the brick is 4″ thick and carries no weight. It is just a very thin layer that would topple over if it weren’t tied to the building.
But so what? Why is this important?
Because structural masonry homes are built in a very long-lasting way with mortar that is very different from today’s mortar, and this building system is not well understood by today’s contractors, masons, and homeowners.
These walls are constantly damp below the ground. They are plenty strong enough to carry the load of the house. They are flexible enough to handle the small building movements that occur in every building and still last for centuries. And they are virtually maintenance free.
Modern mortar repairs, modern coatings, and modern interior changes are destroying these buildings because they are not compatible. They trap moisture.
The resilience and longevity of the old structural masonry homes goes back to the mortar.
I’ll say it again: It all goes back to the mortar.
The old mortar is strong, flexible, and allows moisture to escape very easily.
Modern mortar is super, super strong, very brittle, and holds on to moisture.
If your home is masonry and built before about 1920, please make sure your contractor is using compatible materials.
If not, there are easily avoidable structural problems and moisture problems down the road for you.