Soft (control) joint in an ashlar masonry wall

In a masonry assembly the masonry units are held together by mortar joints. That is pretty obvious, but what a lot of people don’t know is that in a masonry wall it’s also normal and correct to have some joints wall not be built with mortar but instead be built with a resilient or elastomeric sealant. For example in most residential walls, every 20 or so linear feet around the facade there will be a vertical control joint. That control joint will be cut directly through every other brick so that the control joint runs in a straight line.

In the photo below you can see a control joint that was intentionally installed in the knee wall.

In the case above, the soft joint has failed, but that works out perfect for us to see the inside of the joint, just for us to examine and understand. Also, it’s ok that it has failed, it should be expected that control joints fail many times within the life of a masonry wall. They require a comparatively advanced maintenance schefule. Typically a masonry wall should last over 50 years without much maintenance. However a control joint for only last approximately 3 to 10 years before need to be reworked and replaced.

Also, it should be noted that in this open during, since the sealant has failed, you can see there is a backer Rod or expansion board inside of the space of the joint between the stones. That is intentional and done correctly in this photo. That expansion board does a couple things to benefit the joint. It allows for movement of the stern without having a hard pinch point and simultaneously provides a backer so that the ceiling does not have a deeper opening which needs to be filled. Sealants have special limits to which they can be applied. For a sealant to work properly it can’t be applied beyond a certain Dimension, in this case having a opening that is roughly 3/4 of an inch x 3/4 of an inch, that is inappropriate space.

In the photo below you can see a regular hard mortar joint in the same wall. We show this here just for comparison.

And also, here for comparison in the photo below you can see a control joint which has not failed. The sealant used has not been applied very smoothly, but all the same functionally this control joint is still working the way it should. It is an impermeable membrane which keeps water or moisture out of the joint. And also, because this is soft and has much higher flexibility then a regular mortar joint, it allows the wall to move a little within the 20 foot long section without breaking the mortar or stone the way would otherwise if the control joint was not there.

In this context when we say hard mortar joint we mean a regular mortar joint and when we say ‘soft’ joint we mean a joint that is filled with a sealant and no mortar at all.

Cross section of a retaining wall, ruins on the ocean

The ruins of this retaining wal show a good view of the cross section of the construction. It’s hard to see the base at grade and the footing is underground. Yet you can see exactly how the watertable and stone coping attach to the rubble stone construction of the wall.

In this case the water table is in the stretcher position. For residential homes and commercial buildings, often where you find the water table it will be coincidence a damp proof course, for example at the top of the foundation.

Lined mortar joints

Lining out the mortar joints of bricks was common at about 100+ years ago. The practice is less common today. Lining out the mortar joints gives an appearance of a thin mortar joint of a fine pressed brick.

In the photos below you can see an oxide or or brick dust coloring was applied over the mortar joint to create the appearance of fine brickwork.

Bastard tuck pointing

In the photo below you can see examples of what is known as bastard tuck pointing. Unlike the typical brick tuck pointing done at historic brick buildings to maintain the masonry mortar joints, bastard tuck pointing is normally done at a time or shortly after the time of original construction of a wall. Bastard tuck pointing is done not necessarily for preservation and maintenance of the wall for functional reasons such as protection from the elements and weather, instead it’s done more aesthetics. Bastard tuck pointing is the application of a raised bead of mortar on top of the original bead of mortar used to build and set the stones or masonry units of the wall itself.

Brick Hod

A brick hod is a simple tool used for tending brick and masonry materials and units. The picture below is from a pre-1930’s

In this blog post, we give a special thanks to Mark Stansbury, for permission to repost this image from his blog to ours. Stop by and check out Mark’s site at http://trowelcollector.blogspot.com

Today we commonly use a clamping brick carrier, a clamp with a handle to lift about a dozen bricks at a time, to pick up and tend brick to our masons instead. You may be able to get a sense from the image, but if not imagine the brick hod shown is attached to long pole, all told standing up to the full height of a man.

As one technology changes other technologies, in this case tools, are impacted. Brick hods are still commercially available today and even used in certain cases; however, with long boom rough terrain site navigable forklifts available today our simple industrial ergonomic efficiencies have changed as well. From about 150+ years ago up to about maybe 40 years ago, masonry units were delivered to site on train, cart or truck. Today, we can often get the masonry units loaded by machine much closer to the actual location of installation. However we still have to tend the masonry units to the Mason. Tending is the name for essentially handing the masonry unit to the Mason before the Mason carefully sets the masonry unit in place. Tending sounds very simple, almost unnecessary but it requires a lot of tough, backbreaking labor. Today we more commonly use the clamping brick carrier instead of a brick hod.