<p>I like this picture for several reasons, in just this one photo you can see so many things. This is a historic common brick, not a pressed brick. It&#8217;s a wide mortar joint typical of plaster covered or exposed rear exteroor walls of the time, about late 1800&#8217;s. There are subtle signs of efflorescence salts [&hellip;]</p>

<p>The following pictures are from a chimney we repaired and Tuckpointed BEFORE we fixed it. Some previous contractor went and tuckpointed the mortar joints with something that looks like the small batch cement sold in big box stores in small bags for floor leveling and the like. It&#8217;s hard to tell what the previous contractor [&hellip;]</p>

<p>In this stone masonry wall, some interesting looking stones have been used. The stone in this photo looks as if it has been built like Swiss cheese around a lot of small pebbles. Without having a mineralogist or geological background, I would guess this stone is one of two descriptions: 1. Igneous stone above the [&hellip;]</p>

<p>I was in a DC attic recently and noticed that every one-in-five or so of the roof decking boards had a cement coating. The boards looked just like our modern day forms boards after being dirtied from use. This roof framing is original to the house. At the time of construction of much of DC [&hellip;]</p>

<p>We were on a jobsite last month where there was a section of concrete paving. The concrete paving was old and largely broken up. I wasn&#8217;t expecting this but I found old mollusk shells in the concrete, similiar to the old tabby walls common on the shores of the Carolina&#8217;s. Tabby concrete construction is a [&hellip;]</p>

<p>The photo below shows an example of an old rat slab, a thin layer of concrete applied on top of a dirt floor cellar in historic times. These old slabs were intended for just three purposes: 1. Minimize dust of a dirt floor. 2. Keep rodents, like rats from boring through as quickly. 3. Reduce [&hellip;]</p>

<p>The picture below zooms in on a panel of electrogalvanized corrugated sheet metal, in this case used as a siding material. The exposed layer of the metal panel shown in the photo above is zinc. The panel itself is steel, likely grade-5 mild steel which is easy to cut and less expensive than grade-8 or [&hellip;]</p>

<p>A voussoir masonry unit is a non-keystone member of an arch. The picture below shows an arch without keystone.</p>

<p>It&#8217;s a beautiful sunset looking south into the Pacific from California&#8217;s Sunken City, an incredible seaside terrain. Looking closely at the stony land at the edge of the sea below the the unstable cliffs, it becomes clear that the stone is not a natural formation. The cement where broken in jagged edges and worn away [&hellip;]</p>

<p>We put together a few videos and a lot of info below to explain the process of chemical conversion calcium carbonate calcium oxide. This process is more commonly known as firing of limestone to create quicklime. Quicklime as many know is the key active ingredient in historic lime mortar. Doing a little backyard chemistry, we [&hellip;]</p>

<p>In Caitol Hill we see stair step cracks daily. In many cases, the cause is header failure. At the wall in this photo, taken in NE DC, the cause is actually likely to be either lateral deflection from insufficiently relieved hydrostatic pressures or from differential settlement. It could be that both issues are happening at [&hellip;]</p>

<p>Piping and tubing has led to the development of societies overall. We&#8217;ve been using piping for thousands of years. However, over time our piping and plumbing methods have changed significantly. (Interestingly, the word plumbing comes from the Latin root word for lead.  Plumbers essentially are/were lead-ers.  Because at the time of the origin of the [&hellip;]</p>

<p>Replaced a water heater this weekend and — as always — when replacing a water heater, we drain out the water heater during or before removal. As is common and customary, we found the tank to be full of crud and you can see the water running out red in this picture. This particular water [&hellip;]</p>

<p>There was a time, not long ago, when every house depended on old-time phone wiring for any electronic connectivity.  Nowadays, we clearly have many alternatives to the old-time press button systems.  However, the old wire is still out there, overhead on telephone poles and underground, as in the case of the photo below. Typically, in [&hellip;]</p>

<p>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, [&hellip;]</p>

<p>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.</p>

<p>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.</p>