Basement re-pointing

Late last year I re-pointed (or tuck pointed) some areas of the interior brick wall on the first floor. It was only necessary where I had localized moisture damage.

I am now moving down one floor, into the basement, where the moisture damage is much more wide spread, and as such a lot more re-pointing is needed. There are two general kinds and causes of moisture damage.

The soaked wall

A part of the front basement wall was completely soaked. The source for all the moisture was a disintegrated roof drain that must have had water running down the brick work for years.

Having had the wall open and exposed for a few months now allowed some of the moisture to dry out. Still, we will need to re-point this entire wall section.

Sorry – no images of raking out the joints with the angel grinder. Too much dust for the camera to handle.

Parging trap

The rest of the re-pointing work was limited to the lower section of the brick work in the basement. Above that, the mortar is in pretty good shape.

The line between deteriorated joints and sound mortar coincides with the cement parging on the outside of the building.

parging-01

The parging acts like a vapor barrier or vapor retarder and only allows the brick work to dry out towards the inside of the building. This one directional drying process is not very effective and will cause elevated moisture levels in the masonry. That in turn led to the deteriorated mortar joints on the inside.

Re-pointing these lower sections of the brick work around the basement is only half the remedy needed. To fix the elevated moisture levels, we will need to let the wall dry out into both directions – we will need to remove the cement parging on the outside wall.

Why is the parging there in the first place? Well, it is one of those ‘sweeping it under the carpet’ issues. Rather than fixing a problem, it gets covered up.

The problem here was water damaged brick above the limestone foundation.

parging-02

The solution was and is to replace the brick, keep moisture away from the wall, and let it dry out in both directions.

Hmm, sounds like another interesting masonry repair project, doesn’t it?

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

2 thoughts on “Basement re-pointing

  1. I’m dealing with the aftermath of the same sort of “parging trap” on my 1910 3 flat. It’s nice to see an example of it being death with successfully before I deal with it at my place.

    Something to understand about any exposed masonry wall – it is permeable. Liquid water will work its way into the brick. Stand at the base of the wall, and look up. All that surface area of exposed brick will get saturated with heavy rain, and wind will drive the water well into the wall. That liquid water will work its way down through the brick, masonry and cracks in the wall over time. In this sort of situation, where someone parged the bottom couple of feet of the wall, that liquid water will be trapped. Part of the damage that is done in this situation is that the liquid water near the exterior surface of the wall (just behind the parging) will freeze during the winter and expand inside the brick – that’s part of what caused the exterior surface of the brick to spall off, as shown in your last photo.

    In modern buildings, we build exterior brick walls with two layers separated by a drainage space. The exterior layer is usually one “wythe” (layer of brick) thick, and is spaced off the rest of the wall with “ladders” of galvanized steel. That outer layer is held away from the inner, structural layer, typically about 1″. Any water that works its way through the outer face brick drips down through this drainage space to the base of the wall, where it hits flashing. That flashing is set up to be high on the inside of the wall and runs down towards the exterior face of the wall. Weep holes are provided through the face layer so that water can drain off the flashing and to the exterior.

    The problem with these old, solid brick walls is that there is no drainage space inside the wall. There really isn’t a good way to add flashing or weeps. Someone saw that there was a problem with moisture in the wall as it was originally built, and added that parging for a reason. While the parging only made things worse, that original moisture issue still exists. LIke you, I’m going to remove the parging and repair/replace the brick, but I don’t know that it’s a full, long term solution.

  2. Moisture in an old brick and foundation wall as mine is actually mostly moving up, not down. Although the common brick is like a sponge, I learned that is also dries out as effectively as it absorbs rain. If the wall gets hit with rain, the outermost wythe may get pretty wet, the second wythe only receives a fraction of that moisture content and the third wythe even less (according to buildingscience.com).

    Key is to keep proper drying mechanisms in place, i.e. the right mortar in the joints – and no cement parging!!!. A restoration mason explained to me that the proper lime-based Type O mortar sucks and moves the moisture right out the brick wall.

    Moisture in these old walls cannot be eliminated – and it never was the intent. The issue is more about properly managing the moisture and letting the walls dry out.

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