Sub-Surface Drainage

Water infiltration prevention!

The way water will move and drain

around the house was carefully considered

since our home is being built on a slope

made of clay

in a landslide area

in rainy P'Town, Oregon.

The foundation walls were coated

with a black asphalt/rubber spray

for damproofing

and then an orange drainboard

to keep water away.

We opted for under-slab drainage

since we expect

our daylight basement

will take on lots of water.

The drainage pipe (white)

will be covered

with about 18" or so

of gravel.

There will be a moisture barrier

and then the concrete slab

will be poured

on top.

Was upset by this detail.

The drainpipe was supposed

to be laid along side the footing

instead of on top of it.

It's recommended to keep

the water table below the footing

so that the there is less of a chance

for water to find a crack

in the basement wall.

This mistake caused our first major dispute

with the G.C. (general contractor).

I felt like the drainage detail

I created with help from

the Geotechnical Engineer

was ignored.

We asked them to get the drainage pipe lower.

Here was the fix:

Not ideal,

but an improvement.

The g.c. hired a crew to come

out with an "airspade",

which shoots air at high pressure,

to carve a channel in the clay

alongside the footer.

The drainage pipe w/ filter sock

could then be lowered

below the footing.

I also asked that the footer

be sprayed with the asphalt/rubber

spray to slow water from "wicking"

into the concrete.

They filled the cavity

with clean 2" drainrock

right up to the surface.

All this for a little peace of mind.