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| void material placed within foundation's perimeter (brown rectangles) |
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| polyethylene vapor barrier (yellow), and R5 rigid insulation (white) |
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| rebar over rigid insulation |
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| additional rebar placed around concrete piers |
Despite Denver's recent cold temperatures and abundant snow fall, West Standard has progressed on the construction of our client's Washington Park modern home.
A small break in the inclement weather allowed for partial installation of the slab-over-void system. This system allows the concrete floor (slab) to be suspended above the soil. Thus, protecting the floor from the site's high water table, as well as swelling that could occur in the underlying earth. Additionally, this system was chosen to deliver on our clients requirement for stained concrete floors in the kitchen, dining, and living areas.
The first step for installing the slab-over-void system is to place a void material within the perimeter of the foundation walls. This material sits directly on the soil, and consists of multiple six inch tall cardboard boxes. The Boxes are reinforced with a grid of vertically oriented cardboard fins. The void material creates a base onto which the concrete will eventually be poured. Over time the void material will degrade leaving the concrete floor suspended above the soil.
20 mil polyethylene sheeting is then placed on top of the void material. The plastic sheeting serves as a vapor barrier keeping ground moisture from the overlying insulation and concrete floor. Next, rigid R5 insulation is placed on top of the plactic sheeting.
Reinforcing bars (rebar) are then set in a grid pattern. Concrete is very resistant to compression, but relatively week in tension. The rebar is used to carry the tensile load, thus, increasing the concrete's strength.
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| finished concrete showing tool joints |
The final step in this process is the pouring and finishing of the concrete floor. In conjunction with the void material and rebar grid, the floor is supported by a series of previously poured concrete piers. Additionally, The concrete floor is "tied" to the foundation wall with a series of reinforcing bars that extend vertically from the top of the foundation wall. The exposed length of each reinforcing bar is bent to form a right angle with the foundation wall.
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| finished concrete showing six inch slab |
After the concrete is finished the floor must be protected from the cold ambient temperatures while it cures. To accomplish this, the aft floor will be covered with insulating blankets, and the front portion will be enclosed in a tent. Tenting, although more labor intensive, allows for the best possible finish. We are tenting the portion that will ultimately be exposed stained concrete. Blanketing tends to leave a slightly blotchy finish, and this was acceptable in the areas that are to be carpeted.
West Standard is a Denver, Colorado based architecture firm and custom home builder creating modern sustainable experiences. More information may be found at:
www.WestStandard.com
