Block Basements: Part Three

This is the third in my series on block foundations and we now look at the numerous kinds of materials, coatings and membranes on the market that are used to rectifying a wet block basement. One thing to get clear from the start, the terms dampproofing and waterproofing that are often used by some unscrupulous contractors as the same thing….they are not! Dampproofing is coating that is applied to resist soil related moisture permeation into the blocks, it’s generally an asphalt based coating not unlike the driveway sealer you put on your asphalt driveway. In an extremely well drained soil around a home they will have some effect but those of us in the trades are fully aware it looses its effectiveness in less than 5 years. Waterproofing is just that, a system to effectively prevent water from entering your block basement. This is done by excavating around your home and applying a waterproof system.

The next myth is the roll on…brush on…spray on coating that is applied to the inside of your basement walls. Think of a plastic cup with a small hole drilled in it. If you apply the band-aid on the inside and fill it with water the entire band aid is held in place by the water. If you apply it on the outside you are reliant upon the adhesion abilities of the band-aid. In effect if the porous blocks are receiving the moisture we all know they do then this kind of coating has a tough job ahead of it, one I have yet to see as long term effective. There is one interior water soluble rubberize material called Blue Max that advertises itself as a waterproof paint. If you read the specs closely you will find they recommend 2 gallons per 100 sq ft and application to the thickness of a dime. In an area of casual dampness it may be worth a look, for repeated dampness or water invasion I would be hesitant.

 Now that we have got the myths out of the way we can look at the different kinds of actual external coatings and membranes that are on the market. It is a long list so I am going to stick to the most common types. Bentonite clay is a powdered mix that is also used in some toothpaste. It was the first recognized waterproofing material and entered the residential market in the mid 60’s.  Once the mix is prepared by a trained installer it swells up to form a sticky gel upon application. It is also available in sheet form. The drawback to this material is it must be shielded from rain and if there is any free flowing ground water it will erode it away.

The majority of reputable foundation contractors utilize a rubberized liquid coating or some form of continuous membrane. There are numerous kinds of membranes on the market. Yellow jacket is one type that is applied over a preparation coating and is set into the coating. It is an open weave glass fabric material that is colored so the installer can see that they have covered it fully. It is applied in layers to form a waterproofing covering. It seems that the word “Blue” is attached to many foundation materials. One make is called “Blueskin”, it is a self adhesive membrane that is applied over a sealing primer compound that has been applied and cured.  Another membrane is called dimple wall and is made by a couple of companies. This rubberize sheet is designed to offset the actual membrane from the wall by 5/16” by means of a dimpled surface. The manufacturer claims it keeps the soil away and allows any dampness in the blocks to condensate outwards onto the membrane and then drain down to the drainage tile for removal.

There are also a number of different kinds of brush…roll….spray on rubberized coatings on the market. One maker is called “Tuff-N-Dri. Its product is a spray on coating called “Code Blue” (there’s that blue again!) This product is only applied by installers who have been trained by Tuff-N-Dri. One of the largest manufacturers of sealants, coatings and membranes is Bakor. They are the makers of Yellow Jacket and Blue-Skin. They also manufacture a line of liquid applied membranes that are very popular with reputable foundation companies. Some installers will cover their liquid membrane with rigid foam insulation. This has two benefits, it helps reduce the cold intrusion into the foundation, similar to an ICF foundation and help protect the liquid coating from any damage from rocks or lumps of soil in the material used to backfill the opening around your foundation. There are other kinds of waterproofing systems on the market; Thermadry is a system of 2’ by 8’ tongue and groove panels that are channeled to deflect water for example.