This photo shows a good example of a historic damp-proof course in brickwork.
This house was built about 110 years ago. A piece of slate tile was installed between the mortar joints of the lower course of brick. Here in this picture you can see where we picked away at the loose mortar. Over time, the mortar was not tuck pointed, and therefore, the mortar at this location is loose and deteriorating.
When we checked the condition of the mortar, we found this piece of slate tile shown in the picture. The slate tile was installed to provide a damp-proof course. Essentially, the slate tile is impermeable to moisture. The slate tile at this location is almost exactly the same as a slate tile on a roof.
The damp-proof course prevents or deters rising damp (moisture) from affecting and deteriorating the upper portions of the wall.
Click here to learn more about rising damp.
Formstone was invented and primarily first used in Baltimore, MD. Like a cover-up tuckpoint, formstone may simply be a cheap way of hiding something that looks even worse.
In the top right corner of the middle house in the photo below, you can see the brick substrate behind the formstone where the formstone has delaminated.
The running bond pattern is not found very often in Capitol Hill. American bond, for example, is much more prolific. Since each wythe of brick in this bond is built with all stretchers, there is no interconnection between brick wythes.
This wall is built in a running bond pattern. Photo was taken here in Capitol Hill, DC at the exposed side façade of a rowhome.
At alternating courses, in this picture, the brick on the left side next to the corner is a queen closer.
The queen closer is cut lengthwise to allow the course of brick to fit within the allotment of space. The amount by which it is cut is removed to make up space for the remaining bricks in the course.
Terracotta has been used for thousands of years. In simple terms, terracotta is low-fired clay.
Inset details made from terracotta below or between vertical window stacks such as in this picture are common in the historic construction of Capitol Hill.
Header failures are not rare in the 100+-year-old masonry construction of Capitol Hill.
In some cases, the reason for failure is as simple as natural deterioration with age.
If you look closely at the picture, you can see there is a vertical zig-zagging crack in the brick and brick mortar, where the structural load path has a differential settlement.
If you look closely at the eyebrow or segmental arches above the windows in the picture, you can see that the bricks in the soldier position around the segmental arch have shifted over the years and are falling out of place at specific locations.
In other cases, contractors who did not know about working with historic materials have used the wrong materials and it actually accelerated the degradation of parts of the building assemblies. We covered spalling in another post.
In the photo below, you can see a double-wythe brick wall cut right down the middle. So, what is a wythe?
Middle English from Old English withthe(“withe”)
A wythe of brick is a single vertical assembly of units. In this case, and typical with above grade exterior or even interior demising walls in Capitol Hill the wall is a double wythe.
You can see a perfect cross-section of the bedding mortar and stretcher mortar between bricks. The vertical joint between wythes is called the collar joint.
In this picture, you can see where a wall was dismantled, exposing the typical functional assembly of common brick. You can also see that this is a double-wythe brick wall. Whereas in the picture above you can see the bedding mortar between the Shiner faces of the brick, in the picture below, you can see the prepend mortar, in section exposed, between the rowlock faces of the brick.
In the photo at top, you can also see the (otherwise, normally completely-hidden) collar joint between the two wythes.
Oftentimes, what is otherwise just simple brick can be used in many ways in our Capitol Hill historic façades to provide variation and accent. Brick set at an angle so you can see both the soldier and sailor faces or the spreader and shiner faces at the same time is called “cogging.”
Between a window header and a sill of windows above, it is common to see an accent section built into the exterior masonry.
Brick cogging used as an accent.