Does our leaky basement need ‘blue skin?’

Hey there, time traveller!
This article was published 18/09/2005 (7404 days ago), so information in it may no longer be current.

QUESTION — We enjoy reading your article in the Free Press and had a couple of questions for you. We have a completely renovated 1890s, three-storey home with a cement basement. We have always experienced some water coming into the basement in the spring or during heavy rains in the summer.

This past fall we completely gutted out the false floor, carpets and panelling walls right down to the cement. We replaced the sump pump and deepened the pit, which has helped. To better insulate and stop any seepage we sprayed the basement walls with two to three inches of commercial building spray-on insulation that dries completely hard. We replaced our eavestroughs and downspouts on the house to move water away from foundations. Our soil is very sandy here and the water table is high, so as a result, water comes in from cracks in the basement cement floor.

We would like to know, in your opinion, would the “blue skin” be suitable for our floor?

Thank you.

–Angie & Keith Mclean, Macgregor, MB

ANSWER — For the information of the readers, a “blue skin” membrane is a rather generic term for a self-adhesive, rubberized waterproofing membrane normally used for foundation and walls on the exterior of buildings. One popular manufacturer of foundation coatings makes this product in a light blue colour, hence the name. We will look at the normal function of this material and explore your request for the unusual use you suggest.

One manufacturer of this type of product, Bakor, actually produces several types of membranes with the trade name Blueskin. There are a couple of variations of this product, with the first being a self-adhesive membrane, and the other a thermofusible or torch-on product. The latter is often used when the temperature is below -5C, or an exceptional bond is desired. It is not appropriate for your case, due to the need to apply with a large propane torch, so we will discount its use. The self-adhesive membrane may be more desirable for your situation, as no special tools or safety precautions are required for installation.

The two main things to consider when using any product that is not specifically designed for the situation is whether it will work, as intended, and whether there are any safety or health concerns. To address the first issue, you must ensure that the concrete floor slab is completely clear of paint, oils or other material that will prevent adhesion. Next, the concrete must be coated with a specific primer designed for this membrane and allowed to dry before application. Once dry, the membrane may be cut to fit and applied and rolled to smooth. The problem here is that these waterproofing products are designed to be applied on the exterior of surfaces, to prevent moisture from leaking through the surface of the area covered. In your case, the moisture may still be able to enter underneath the membrane, through the concrete, because it is installed on the inside of the problem area. These membranes are excellent for use on foundation walls, balconies, and a host of other exterior areas, but are not designed for inside use. There should be no physical reason that the membrane could not be applied, but we must also address the second item of consideration before continuing.

Is there a health or safety concern with this material in the home? These rolled sheet goods are rubberized waterproofing membranes that adhere to the surface with a bitumen-based backing. In other words, the black, sticky, bitumen-based backing of the membrane is what gives it the good waterproofing qualities you desire, but it may also release an offensive odour or dangerous chemicals into the home. For simplicity, although not completely accurate, this may be similar to spreading tar or roofing cement on the floor in your home. For this reason, I don’t think it should be used for your application.

A better solution may be to reinstall the wooden subfloor, with pressure-treated wood for supports and sheathing that will be highly resistant to moisture damage. These products may also release chemicals into the home, but they should be less toxic than bitumen-based products. Another solution is the use of floor panels bonded to another product originally designed for exterior foundation use. This dimpled plastic membrane, often referred to by one manufacturer’s trade name Delta, is now available bonded to small, tongue and groove panels of OSB sheathing. These panels can be applied directly over the damp concrete floor, as the bottom is corrugated plastic, which will not be affected by the moisture. The spaces between the dimples will let seepage drain into the floor drain or sump pit.

Care should be taken to allow a reasonable amount of ventilation for anything used above a damp concrete floor, to prevent mould growth. The repairs and modifications you have done on the exterior of your home may also help minimize moisture intrusion through the walls and floor. It is better to try and prevent the moisture entering the home, and deal with it if you get seepage, than try to stop it once it has already saturated the concrete walls or floor slab. This may only keep the moisture inside the concrete and cause quicker deterioration to the concrete itself.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors – Manitoba (www.cahi.mb.ca). Questions can be

e-mailed or sent to: Ask The Inspector,

P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, Man., R3P 2G9.

Ari can be reached at 291-5358.

trainedeye@iname.com