Dealing with Rising Damp in Building Reconstruction
Old buildings with stone or brick walls face problems with capillary moisture and efflorescence
While China is building new cities as fast as possible, Eastern Europe is faced with a challenge on the opposite end of the scale. With a negative population growth and an abundance of old houses, it makes much more sense to rebuild the existing infrastructure than to build new.
I'm now visiting Eastern Europe. Many of the villages have houses built prior to World War II. Fortunately, the thick stone walls and strong timbered roof structures make for solid buildings that withstood years of abandon and can serve for many more centuries once refurbished.
One of the greatest causes of deterioration is rising damp. Moisture in the soil wicks up the stone walls, through the porous mortar, and continues to move from wet to dry up the wall above grade. It can dry to either side of the wall — to whichever side is dryer. This means that if you have a nice dry interior, the moisture will move inward and evaporate into your dry air, pulling more moisture up behind it.
All fine, as long as you really don't mind mold, wanted extra humidification, and are willing to leave your walls with a chalky, porous finish. Sort of a cave-man décor.
BLOGS BY VERA NOVAK
The other option is for the moisture to wick toward a dry exterior — usually via whatever covering you have. This was the primary reason for paint blistering and peeling off my wood siding in a previous house, and the cause of the plaster finishes of these walls staining and crumbling. Not good.
Plastic dimple mat, perforated pipe, and landscape fabric
Not surprisingly, these Eastern European countries have developed the tools and techniques to address the problem. There are two points of attack, depending on the source of your water. If the soil is relatively dry, waterproofing and good drainage might be sufficient to prevent surface water from reaching the basement walls.
Recently, in a little village in Slovakia, I approached an older gentleman who was in the process of retrofitting the waterproofing details around the foundations of his 110-year-old home. He had dug down 3 feet, and installed plastic dimple-board and a landscape-fabric-wrapped drainage pipe; then he backfilled with gravel.
He told me that all the installation details can be found on Google. (Gotta love it). He then proceeded to explain that the edge of the dimple-board needed to be covered, and that there was a poly / acrylic-type mortar that can be used in place of concrete to effectively continue the waterproofing up the foundation for 3 or 4 feet. It comes in a pebble coating, or can be the backing for a more traditional stone foundation. The stones are isolated both from the wall behind, and the foundation below.
I was relieved to hear of this home-improvement plan, since I had seen far too many of these dimple-boards just poking up above grade an inch or more, hanging out on the outside of the foundation finish. This is a problem, since the gap allows rain to flow down between the board and the side of the building.
I checked into some of the company websites and found that their installation instructions often stop short of discussing how to finish the top edges. (It's not their problem ...) A very definite gap in information that could sabotage the entire effort.
The alternative, if you don’t have the space to dig around your foundation or are in an area with underground moisture, is to insert a water-impermeable layer in the foundation wall just above grade. I looked into this after my trip to England last year (see my blog post, "Dealing with Damp"), but have found a bit more information through Google Slovakia. (I need to figure out how to “trick” the location of my computer so I can virtually be in different countries when I am using Google.)
Silicone cream or stainless-steel flashing
The easiest method is drilling holes at regular intervals in a mortar joint and filling the holes with a silicone cream, which will theoretically spread sideways through the mortar bed and create a waterproof layer.
However, in many stone foundations, there is no level bed of mortar. The solution for this scenario is far more complex, and calls for cutting (or also this link) through the foundation and inserting a rubber or stainless-steel flashing. (See also a video of an installed steel sleeve).
The great lesson for me is that buildings can be constructed in a way that can last for a few hundred years. This can provide a durable infrastructure that is available for adaptive re-use, and thus a longer service life to extend the value of the embodied energyEnergy that goes into making a product; includes energy required for growth, extraction, and transportation of the raw material as well as manufacture, packaging, and transportation of the finished product. Embodied energy is often used to measure ecological cost. of the building materials.
It also points out the importance of not taking any shortcuts when building new. Waterproofing and inserting a capillary break between the footings and the foundation wall are very important and should be included in the new construction, when it is the least expensive and easiest to do.
This is a lesson we tried to hammer home to the ICFInsulated concrete form. Hollow insulated forms, usually made from expanded polystyrene (EPS), used for building walls (foundation and above-ground); after stacking and stabilizing the forms, the aligned cores are filled with concrete, which provides the wall structure. builders, as this building material is so well suited to legacy buildings.
Dr. Vera Novak was recently awarded a PhD in Construction by Virginia Tech. Her work is dedicated to increased depth and breadth of sustainability in construction, by leveraging the points of greatest potential impact. She is currently working on optimizing corporate sustainability practices to support regenerative design, as well as adapting a lean thinking process for smaller scale projects. She also writes the Eco Build Trends blog.
- Vera Novak
Jul 23, 2013 10:39 PM ET
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