Tom:

If you get the house, all the several suggestions made should be quite
helpful insofar as reducing the hydrostatic pressure on the foundation
walls.

The costs are considerable as Lyle mentions, and the selling price value
of the house should be adjusted accordingly.

Divert the surface water away from the house.

Some type of concrete surface drains could be constructed higher up on
the slope. What is happening with the higher neighbors? Is it possible
that they have been thinking of some garden designs involving
water-diverting hardscaping?

The photos show surface erosion. ground cover plants may help hold the soil.

Lyle may be able to offer suggestions regarding the treatments for the
exterior foundation walls, drain fabric panels, and footing drains. He
is the local expert.

An interior sub-floor tile drain system could be installed. Also, a sump
pump in a deep pit that is occasionally active in combination with
perimeter sub-floor interior foundation tile drains could lower the
interior water levels.

I would additionally suggest that the HVAC system for the basement be
isolated from the rest the house. The water vapor laden air should be
exchanged with dry air from the outside to carry out the moisture that
is damaging the wood structure of the house. Via evaporation exchange
air can transport a considerable amount of water to the outside, and
also lower the moisture content of the wood structure of the house. An
air to air heat exchanger with in-duct fan would conserve energy, and a
condensation water drain provided (Lossnoy is one Japanese brand).

80mm thick polyurethane or polystyrene foam insulation panels adhered to
the previously water sealed (but not possibly water tight) concrete
walls will stop or considerably lower condensation on the walls.

Insulate the exterior walls at the floor joists with +20cm of lightly
packed fiberglass, and add an impermeable vapor barrier inside of the
insulation. No higher interior air pressure should be allowed to carry
water vapor through any gaps the the outside or through the insulation
where water vapor can condense into water.

Ralph Hertle

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