Continuation of Foundation Construction

Block stem-wall for slab.

The long east-west axis of the house faces five degrees west of due-south to take best advantage of the site's solar window.

Plumbing rough-in.  The plumbing was "stacked" on the floor plan to limit cost and distances from the water heater.  All supply lines are insulated.

Materials are staged.

Wild cherry felled from the building site and milled for later use as bookcase facing.

Installation of radon mitigation system (just in case).

The area inside the stem-wall is filled with pea-gravel and thoroughly compacted.

Since the finished slab will account for the majority of the thermal mass inside the building envelope it's really important to create a "thermal break" between it and everything outside.  Unfortunately physics dictate that the load needs to be carried straight through the stem-wall to the footers without any insulating material in between.  Despite this it's still possible to insulate the stem-wall from the outside air with rigid fiberglass (termite-proof) and from the inside of the slab with R-10 extruded polystyrene.   This will provide enough separation that the slab can act like a battery storing solar warmth throughout the day and releasing it throughout the night.

The footers for the support columns were poured to a precise depth to allow for insulation right up to the posts (as opposed to only insulating up to the outside edge of the footers).

The entire slab will have 2" of extruded polystyrene underneath.  And no, Lowes is not a sponsor of this blog.  We just happened to have a coupon.

Where the horizontal layer of slab insulation overlapped the vertical stem-wall insulation we cut a line 2" inside to eliminate any small voids between the extruded foam and the gravel base.  This will prevent settling later on.  In retrospect we would have simply positioned the stem-wall insulation right up to the lip of the deep-cut chair block rather than leaving it 2" below.  This would have eliminated a step.  Hind-sight is 20-20.

Another gorgeous day on the job site.

The cement for our slab has a higher concentration of fly-ash mixed into it.  This provides a superior mix while entombing waste from coal-fired power plants.  We also upped the strength to 4000 pounds per square inch since the slab will be our finished floor.  Its important that the slab be exposed for solar heat gain.  We will acid-etch and seal it for beauty but carpet, hardwood, etc. would defeat it's use as thermal mass for a "fly-wheel" effect.

A thing of beauty!