Identifying and Addressing Cracked Stone Header Effectively
In this past week, we took a look at several different types of failed brick opening headers and talked about some of the issues related to lateral deflection and deterioration of historic brick mortar joints (and associated repointing or tuckpointing). Often historic brick mortar joint deterioration will lead to overall failures that are much more significant and almost reach the point of catastrophe. Brick pointing, by comparison, is just a very limited element of repair and restoration, much simpler than rebuilding after a catastrophic collapse, or failure. It’s interesting that something as simple as just masonry restoration can prevent something as major as collapse of a portion of a building.
Brick repointing, often mistakenly referred to as tuck pointing, here in Washington DC, is a relatively direct process of removing material mortar at the outside edge of an exterior masonry partition. Generally this work is done at the side and rear facades, more often than the front facade because pieces come of the mortar at the front facades of historic brick buildings here in Washington DC was built with a slightly tougher lime mortar.
We show a closer view of this area of failure and collapse, in other pictures below, but in this picture you can see something unique. When you look closely, you can see that the brick at the sidewall of the building, in the left of the photograph, is different than the brick at the front facade. Not only does it look different in color, but it’s a different type of brick with different functional characteristics.
The brick at the side walls of the building is referred to as a common brick. Common bricks are softer and have a lower density and higher permeability. They deteriorate at a higher rate because the mortar of those bricks was also generally softer and the ratio of mortar to brick is actually higher. That means there is a higher amount of mortar per brick, per typical metrics like volume, weight, or area.
The picture below shows a picture of a historic brick building, with a radius turret at the front facade of the building.
In last week’s blog article, we talked about some of the issues of lateral deflection and differential settlement. Lateral deflection is essentially the bellying or expansion of a facade or vertical partition in a horizontal type of shape. In other words, when a wall starts bowing out, like growing a belly, that’s a form of lateral deflection. By comparison though, another one of the big issues or categories of masonry failure is differential settlement. Often, these two issues of both differential settlement and lateral deflection, go hand in hand because they happen to the same areas of buildings at, basically, the same time.
The picture below shows a closer view of the failed header and the area above that header. The brickwork in that field area has a stair step type cracking. You can see that someone, in the past, has done a very poor job at an attempt at repair to that area of stairstep cracking. Their repair did not help, for a litany of reasons. One of the reasons it didn’t work was because it’s probably overly sparsely applied.
They should have repointed a much larger area where mortar joints had deteriorated. Also, it looks like they used the wrong type of mortar. This darker type of mortar used a harder Portland cement instead of using the proper lime mortar. That difference is very important but doesn’t happen to be related to the exacerbation or continued damage shown here. Plus it’s so sloppily applied it looks like they probably didn’t rake the joint properly before application.
This picture, shown below, shows the closest view of all. From this perspective, you can see several elements in the overall sandwich of building materials. If you look very closely at the details, it’s very interesting. First, if you look back into the shadows beyond the stone header, you can see that there is a structural lintel hidden inside the wall, on the inside of the stone header.
The stone header is not thick enough to make it all the way from the exterior facade, into the interior exposed portion of the finished surface of the building, so in this case, a structural header has been installed, similar to the very prolific segmented arches we find here all over Washington DC. In this particular case without enough integration between the wythes of the masonry the header sheared and split into three parts.
In this coming week, we’re going to look at another set of photographs from the same building that we looked at at the start of this article, but show how the same type of cracking continues at other windows within the same facade due to similar issues of lateral deflection that are prolific throughout the particular exterior wall.
We can Help
Our company focuses on historic restoration more than modern building upkeep, maintenance, and construction, but our company understands both types of construction very well and a full picture well-rounded approach is needed in any niche in the construction industry. Although we focus on historic restoration, repointing, tuckpointing and historic brick repair, our company also has technical knowledge and competencies in the areas of modern and contemporary construction as well as we become one of the leaders in that area of the market today. Understanding both historic and modern or contemporary construction is useful because both aspects help understand the challenges and potential solutions for challenges in building science and construction.
We can help with a variety of historic masonry restoration needs and upkeep, from modest tuckpointing and or repointing to complicated and extensive historic masonry restoration. Infinity Design Solutions is a historic restoration specialist contractor specializing in both historic masonry restoration such as tuckpointing our repointing, and brick repair. If you have questions about the architectural details or facade of your historic building in Washington DC, reach out and say hello and if we can help we’ll be glad to assist you. You can email us or call us on the telephone at the following link: contact us here.
