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GBlist: Questions on concrete sealant & vapor barriers for a below grade living space




> Joseph Charlson wrote:
> > 
> > Questions on concrete sealant & vapor barriers for a below grade
> > living space:
> > 

I agree with John Salmen's comments in reply, but I would offer a couple of
alternates, and another point to keep in mind, relating to insulation of
the basement.

>
> If I was to create specifications for finishing that area I would:
> - - excavate perimeter to footing
> - - slope the footing (applying mortar or cement)
> - - apply zypec to 8" above grade

Unless  there is a major hydrostatic water pressure from gourbnd water, if
you opt to excavate on the exterior, then using a drainage material against
the foundation wall would probably be easire to use and more efffective
than a waterproofing compound such as Xypex. By waterproofing product I
mean such as Drainclad (a rigid fibeglass board), PLaton damproofing
membrane, or other similar mechanical systems. Check with local suppliers
of insulated concrete forming systems for products they use.
 
> - - drain rock and perimeter drainage at footing (do not tie gutter
drains
> into perimeter drainage)
> - - apply foam insulation boards against exterior foundation walls from
2'
> below

I would strongly suggest that insulation should be applied full depth -
wether inside or outside (depending on which is easier related to the
specific construction issues). 

> grade to top of foundation wall (you can use stucco or zypec over the
> foam)
> - - use drainage board or backfill with gravel/sand
> - - create a free draining path area around the house rather than
> plantings
> INTERIOR SPECIFICATIONS: the interior should now be dry and insulated
> - - drywall can be directly laminated to the conc. walls but it would be
> preferable to avoid paper faced and gypsum products - cleaning and
> smoothing the exist conc. or going to a smooth stucco finish might be
> preferable.

Again, if fully insulated, the finish can be applied over foam insulation.

> - - flooring (if you need to install an additional heat source you might
> want to think of running radiant floor tubing to take advantage of the
> existing mass and pour a 1.5" slab over and either colouring the conc.
> or installing tile, etc.

Again, as you are planning to make this a lving space, insulating the floor
as well as installing a vapour/moisture barrier is important. Especially if
you would consider putting in a radiant heating system, putting insulation
under the floor should be considered a must.  If headroom permits, you
could put 2" rigid styrofoam over the existing floor, then a 2 1/2 to 3"
slab that wouyld include radiant heating.
> 

You should keep in mind that a major source of moisture in your basement,
especially in the summer, may not necessarily be ground water working it's
way inside, but rather outdoor air brought inside. Boston has a very humid
summer environment, so the outdoor air brought inside into the cooler
environment, such as a basement (especially an uninsulated one) will start
to condense, especialy on the cold surfaces (i.e. thiose uninsulated ones
in contact weith the ground). 

By sealing and insulating all the surfaces, you raise the surface
temperature, thus reducing one problem element. You'll still have to deal
with dehumidification in the summer (due to outdoor air coming inside) but
it should be a smaller problem. And of course, you get a chance to have
more useable living space year round.
 
****************************************************************************
*********************
Richard Kadulski Architect
208 - 1280 Seynmour St. Vancouver BC V6B 3N9
Tel/fax: 604-689-1841
"Climate adapted, energy sensitive, sustainable and healthy design."
Editor: Solplan Review: independent journal of energy conservation,
building science & construction practice
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