Monday, June 20, 2016

Layer it on

Walkout basement partially poured provides a place for chairs
and after-work relaxation. (All photos by author.)
When Doug and I embarked on this adventure of reimagining our lives after 60 in a different state (NH) and state of mind (rural mountainside), I never imagined I would be writing about building materials with great interest. (Doug may have; it naturally appeals to the scientist in him.) But as much as we are into the wood, we are now into concrete, wraps, and foam.

Excavator Dave fills a concrete form with  more stone.
In foreground, the part of the basement that will not be walkout.
The concrete pads will hold supports, most for the timber frame.

The concrete has been coming and coming. To date, 133.5 square yards of concrete have been poured from more than a dozen trucks and on two occasion with an assist from a huge concrete pump. And don’t think for a moment that concrete is boring. It takes focus, precision, and discipline to make everything right before the trucks roll in. They don’t wait around for last minute adjustments. They have to dump the load and move on. Our basic concrete is 3,500 pound; that means it can take a compressive load per square inch of 3,500 pounds (per square inch!). For the garage floor, part of the basement floor, and several piers (concrete poured in Sono Tubes secured by Big Foot underground forms) that will hold up the screen porch and deck, that strength has been kicked up to 4,000 and synthetic fiber added. Now the concrete of the basement hides layers and layers of other materials.

Doug checking the Stego Wrap before the pour.
Ace, concrete team mascot, eyes some blue board. 

Under the basement concrete there is up to 50 inches of crushed, compacted stone; plus drainpipes to allow moisture to be transferred outside the house; radon pipes to release radon (the house sits on granite, nototious for emitting radon); and sewage pipes. On top of that, a layer of 10 millimeter yellow polyethylene called Stego Wrap further insulates, sealed with special red tape. Then comes the rebar, every two feet secured in criss-cross fashion with metal ties. In some places of the basement walls, 2” thick tongue-and-groove "blue board" further keeps the cold from creeping in. (Dow makes blue board, which is Styrofoaminsulation of extruded polystyrene foam or XPS, which can increase the R-value of the wall by up to 20%; Corning has a similar product in pink.)
The concrete will be sprayed to help it “cure” and waterproof it from minor indoor spills. Another layer of protective tar-based sealant will be painted on the outside of the foundation walls in places where they concrete is not faced with stone. The layers keep coming, and we haven’t even worked our way out of the basement.

All manner of building materials are designed to keep warmth in (especially in -20 degree winters) and allow moisture out; thus preventing mold from forming. So we layer it on. On the structural insulated panels, we will be using a double layer of 15-pound felt (old fashioned) and Obydike Home Slicker wrap (new tech, which provides space for water to escape and pressure to equalize). The standing seam metal roof will have 30-pound felt as well as Grace Ice & Water Shield underlayment three feet up from the edge and in the valleys.

The problem created by all these layers in today’s well-built, energy-efficient home is too tight an envelope. We’ve heard problems of negative-pressure houses filling with smoke when the range hood is turned on and a fireplace is burning. So, add another layer of complexity. We will have to have an air-exchange system to circulate the air and balance the air pressure.

More forms coming on site; more concrete.
The other night, sitting on our green plastic Adirondack chairs waiting for sunset, we wondered if, once the house is done, we will be able to (or want to) look at it and not think of all the layers (and work) that went into the final product.


  1. I'm sure you will be able to focus on just enjoying! With the comfort of knowing all has been well foreseen. Such fun to read your posts!

  2. Thanks for stopping by. We have been lucky with the weather so lets hope that keeps up. I enjoy your posts at Keeps my reading list full (and interesting)!