Moisture – Part Four, Solutions

Part of the solution to the problem of moisture migration is allowing the water to have its way. In above grade walls, that means letting it go through the wall, then redirecting it through flashing and weep holes if possible, and most importantly, using a breathable mortar that is more porous than the brick or stone.

Below grade, keep water from resting on the outside of the foundation walls in saturated soil conditions. Create a drainage system, a way for the water to move away from the foundation, perhaps installing perforated foundation tile at the base footing of the wall with gravel fill. Again, check gutters and downspouts to ensure they are clean and take water away from the wall, extending downspouts at least three feet past the elbow at grade level is a good idea. Grade the soil and pavement materials around the building to encourage water runoff and avoid collecting and pooling near walls.

A digital moisture meter in use

Detecting trouble in advance – The use of a moisture meter can sometimes be helpful in determining a baseline for acceptable moisture content in a historic masonry walls. Because not all masonry walls are created or built equally, all have varying levels of moisture depending on conditions. What is important in establishing a baseline is looking for the wall sections that are performing well.  In these areas, take readings to compare to areas with deteriorating brick or stone. This will put you on a specific path toward understanding what to expect in the future.

Also consider choosing breathable mortar materials like lime putty or hydraulic lime blended with coarse aggregate particles – often the vary material that has turned to dust over the past 100 years. Do not try to make it stronger or better. Just match the old lime mortar and move onto the next project. If the original historic mortar has turned into dust or is falling out of the wall, it is likely a lime mortar. It has done the hard work of absorbing more water than the brick over and over again and now needs replacement. The brick or stone is generally preserved in these cases.

The new lime mortar replacement mixture should match the old mortar and perform as the old mortar did – it to will turn to dust and fall out of the wall in the next hundred years, giving the next generation something to fix.

Lime Putty Suppliers in the US:

U.S. Heritage Group, Inc.

Virginia Lime Works

Hydraulic Lime Suppliers in the US:

Limeworks.us

U.S. Heritage Group, Inc.

Virginia Lime Works

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  1. #1 by Michael Bacon on October 18, 2011 - 9:15 pm

    Thanks for the nice clear explanations of the mortar solutions and your other articles. I work in the mortar business in Indonesia and our problem is similar in that they dropped lime use in the 70’s for very strong cement plaster with a pure cement skim coat finish for all walls inside and out. No need to tell you the results!
    Moisture and breathable walls are misunderstood here too.

  2. #2 by John Speweik on October 19, 2011 - 12:03 pm

    Michael welcome to our blog. Also check us out on LinkedIn in a group called “Brick and Mortar-for real” join us there too!

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