Insulation Work on Basements

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How to Insulate Inside

Insulating a dry basement is similar to insulating a new house, although you won’t be able to choose the material for the walls themselves. There are few problems when new concrete or block walls are already in place, but cut stone walls or rubble may prove to be a challenge with their irregular design and varying heights. Framing becomes difficult although the methods remain the same. 

Common insulation materials for residential useThe steps to insulate a dry basement are the same as with new house construction: glue a piece of tarpaper-type moisture barrier to the concrete wall just below the grade before folding up to glue at the bottom of the interior vapor barrier.

Usually the basement wall uses standard framing techniques; however, a small stud wall of 2" x 4" is usually laid 4", or 100 mm, away from the foundation wall. This gives more wall-cavity space for insulation without extra use of framing material.

An alternative to normal batt insulation is blown-in fiberglass or cellulose. Using these materials gives total coverage as well as increased packing density which is useful in areas that are hard to insulate (such as along plumbing lines, around wiring, and in electrical boxes).

The other finishing aspects are the same as for a new home.

How to Insulate Outside 


Before starting any insulation work, all outside features must be removed to prevent obstructions. This means decks, trees, stairs, walkways and anything else that might get in the way.

Identify the entry points of power, water, septic tank lines, sewer, telephone, gas, and other services to the house. If unsure, your local utility company can help identify the paths of pipes and wires, normally at no charge.

Decide beforehand how to get rid of the excavated dirt. Spread a polyethylene sheet on the grass to avoid a mess and for easier cleanup. Tarp can also be used. Bear in mind that there will be a lot of dirt – use a big sheet!


How to install external basement insulationBe careful! The soil can be loose during excavation work and may drop back in when walked on, potentially causing injury or even death.

Excavation works should be from the footing’s top all the way down. 

Do not dig anywhere below or close to the footing base. This can cause the foot and house to sink. 

CAUTION! Old rubble stone walls require surrounding soil support. When in doubt, consult an expert.

Preparing the Foundation Wall

Clean the foundation wall well with a brush. Scrape off all loose concrete and rubble.

Should there be any damaged or missing concrete pieces, you should apply a parge coating or waterproof masonry cement on these areas. Let it dry.

Put damp-proofing compound, which is a tar-like substance, onto the foundation wall from the top of the footing to grade level.

Check for footing drains. If there are none, decide whether you can add some. The drain is a flexible pipe that has thousands of holes along its length and a pantyhose-like liner to prevent dirt and sand deposits. They’re easily added if not already present.