One somewhat worrisome thing was the downspout at the rear of the house,
that brings all the shed-dormer roof runoff out to one of the drainage
pits.
The lowest junction is right by part of the foundation wall, and if
that particular bend were to become disconnected then all that water would
dump on the ground right by the wall and probably find its way into the
basement fairly easily.
It's the same lower bend that received the "silencer" under the two-story drop, and is held together by several zip-screws *and* meta-supported by suitable blocks underneath the horizontal run. It had already been observed to leak a little and I wanted something besides a little sketchy grade adjustment in dirt to make sure any water landing in that area would be positively directed away. Waterproofing the wall itself is NOT an option because of the impermeable foam insulation on the inside, thus the only way soil moisture rising from capillary action can dry is outward. Sealing the wall, even over a limited stretch, would likely spell slow doom for the ungasketed sill area on top of it and besides, such treatment would have to also continue substantially below grade since freely infiltrating water would be right next to it all the way down. The right answer was to make sure the water went elsewhere. The solution would also have to integrate with, or at least not interfere with, the splash dissipation system under the gutterless cheekwall-roof ends -- simply an area of half-inch angular stone laid directly on the ground, which was already starting to get overgrown with stuff poking through it and thus needed a bit of rework. So it was time to re-engineer this entire area and accomodate the two relevant drainage systems going through it in a more robust fashion. A secondary protection system could conceivably be all above ground, and thus commensurately ugly. My long downspout extensions and their reclaimed-flue-pipe anchoring system were already somewhat "industrial" looking, and even though the soil right next to the house generally stays too dry to support plant life I wanted to at least give some form of ground cover a fighting chance to grow in and build some token amount of green stuff toward the wall. [Images are linked to larger versions.] |
The drain-plane would be this old bit of aluminum flashing, which had last served to help protect the head of the basement-bulkhead [visible in the main writeup at the end of part 06]. It had since been lying on the ground under a small pile of junk wood for about two years, but was still entirely serviceable with only a couple of small screw holes to patch up. I ran doubled layers of aluminum tape along the top to serve as a somewhat more flexible leading edge, that would self-align closely against the cinderblock once dirt went in on top of it. |
The idea here certainly isn't new -- there are some nicely detailed
precedents in articles over at
Green Building Advisor [where it's an "underground roof" instead], and
Fine Homebuilding,
all presumably stemming from Bill Rose's
original article[PDF, 1.2 Mb]
from 1997.
While the primary intent is water management, some new energy-efficient construction might use a layer of 2" or so foam insulation set at a similar angle but run out six or eight feet from the foundation all the way around the perimeter, forming an insulated underground "umbrella" to both deflect drainage water and also insulate a much larger volume of earth around the building envelope against seasonal temperature changes and frost penetration. As tempting as such a project might be for this place, it's far more digging than I'm up for at the moment and of dubious value while the block wall itself is still open to the cold air. [But see the eventual solution to *that* problem!] I also didn't bother specifically sealing the upper edge to the wall, figuring that packed earth right along there would be enough of a retainer. |
The rest of the backfilling was pretty straightforward and doesn't really
need more detail; but I didn't bring everything back up to grade just
yet. I wanted to rework the splash catcher in a more elegant fashion,
and left enough of a pit to sink another thin bed of rocks and then a gentle
"vee" of bricks right in the same area under the cheekwall roof end.
The splash-dissipation stone would sit on top of that instead of the dirt,
somewhat better contained against being scattered away and protected
against weeds growing up through the middle of it. Small gaps
between the bricks would let the caught water escape down into the soil.
We couldn't possibly imagine where the idea of bricks held slightly apart as a drainage component came from, now could we... |
A few months later I finally got around to reworking the splash pad under the other cheekwall, which was similarly beginning to disappear under random plant growth. Work began with collecting and cleaning off the existing stone, this time made easier with a temporary sieve from 1/4" mesh hardware cloth. The relevant catch area was re-eyeballed relative to the roofline and carved into the ground with fairly sharp edges, trying to disturb as little of the surrounding soil as possible. |