Building a bullet proof slab


After last week’s below slab insulation, the next step was to install a strong vapor barrier, rebars and concrete.  We wanted a very very air-tight and water-tight slab.  North Star Foundations answered that request with rolls of 15 mil Stego Wrap, the vapor barrier of choice for Passive House builders.  We had only heard about the material, but when we saw and felt it, we were immediately impressed with the strength and thickness of it.

See here for more info on Stego http://www.stegoindustries.com/technical_info/the_advantages.html

To give people an idea of how this vapor barrier compares with most vapor barriers, most homes use a 6 mil vapor barrier that feels like a thick garbage bag, the Stego is so thick that it is difficult to penetrate with nails.

North Star painstakingly installed the wrap, taped the joints and all the penetrations.  In order to ensure the we have a nice sealing edge, the wrap was pulled up and temporarily secured onto the wall studs, which we will trim off when we are ready to seal the perimeters.  See below:

North Star fabricated and laid steel reinforcements into the thickened slabs and footings.

We were ready for the pour.  The concrete was mixed with nylon fibers to help minimize cracking as the concrete dries and shrinks.  Using the nylon fibers also means we did not need to build wire reinforcements, saving time, money and resources.  This entire process was a huge scramble between foam insulation, slab building and inspection.  On top of that, our plumbers decided to come and connect the sewer.  The weather was again a huge issue too because when it rains a lot, our 6 inch foam insulation without the concrete holding it in place becomes a giant floatation device, so we wanted to pour the concrete as quickly as possible.  The concrete supplier showed up way late in the afternoon which caused work to continue into the evening.  Sorry neighbors!

North Star did a kick ass job getting everything done within a small window of time.  The result is the air and water-tight slab we were looking for.  It’s probably bullet proof too, though we did not test it.

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