A beautiful example of red wash with white penciling.
Limewash is mixes of lime and water, with or without admixtures to make it more durable. Some of these additives include salt, blood, and milk. Limewashes and lime paints were found on both rendered and bare buildings to provide a level of protection to the masonry.
Jeff attributes those large, sloppy mortar joint obvious on bad repair jobs to one of two things: one) filling out the mortar too far, causing a 3/8″ mortar joint to appear more like a 3/4″ mortar joint; or two) using an angle grinder to cut out mortar joints. To repair the former, he recommends leaving the mortar contained to the mortar joint and finish it to just 1/8″ of the face of the masonry. For the latter, if you find it necessary to remove historic mortar by mechanical means such as a grinder, the mortar is most probably performing satisfactorily and should not be touched in the first place. If it is Portland cement (in the form of a later repair) that needs removal and it is deemed necessary for the use of a grinder to do the job, only use a blade that is less than half the width of the joint (i.e. 3/8’ joints the thickness of the blade would be less than 3/16″).
Unfortunately, it is all too common that a grinder is used haphazardly and takes out not only the mortar, but also the tops and/or bottoms of the brick as well, causing a nice tight 3/8″ joint to become 1/2″-1/4″! This irreversible damage causes the historic masonry to forever be changed.
Sometimes paint has a tendency to bubble up on the inside of plaster walls. At first, you’re apt to think that this conditions means that moisture is penetrating the brick walls and the wall is in need of re-pointing.
More than likely, according to Jeff, it is not due to re-pointing. Rather, it is a sign of moisture in the walls. Historic masonry is breathable. It allows moisture to travel through the masonry and either return through the semi-porous masonry exterior or travel completely through the wall and dissipate through the interior plaster. When a common paint is used to finish traditional lime plasters, this breathability can be inhibited causing moisture retention and the paint to bubble. The best way to prevent this happening is by using a traditional paint such as a distemper or limewash.
If your walls do need re-pointing the main thing to keep in mind is that you don’t want to change the character of the exterior brick.
In this case, Jeff suggests first looking-really looking- at the building. Take a survey and check out the various details that make your house unique. Check for the original joint details (such as overhand struck joints, bird’s beak, double struck and ruled) in order to determine the way the masons finished the mortar joints. Follow this technique in any new work. This will help keep things look great. Check for colorwash/penciling/stucco/limewash, all of which are things that may have been removed or worn away over time.
If your brick house was painted some time in the past, pay attention to how it is repainting. Paint can affect the longevity of the brick and mortar. Often the use of a latex or other modern paint coating can hold moisture causing the mortar and brick to retain moisture. The moisture may freeze, causing spalling and failure of the host masonry.
Jeff recommends to remove old paint off the house before re-painting it. Although some paints will cover and coat modern latexes, the problems will remain under the surface. It may look fine, but the mortar won’t perform as it should.
Replacing Missing Bricks