Information about design and construction of earth sheltered homes and a journal of my own progress

Life After Shotcrete

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Posted on August 23, 2014 by

Since the shotcrete went up, I have been working on other things such as getting my drain tile in and getting the basement plumbing done. That is covered in the previous post (posted later in time, but shown lower down in the list of posts because of its date).

This is how things looked after the shotcrete was finished (and we got down the drain tile)

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Progress is being hampered by the fact that the shotcrete left a lot more concrete on the floor than expected.  Instead of being a thin crust that breaks easily, it is 2 to 6 inches thick and pretty solid across the whole floor.  This was mostly due to shotcrete blowing thru the lath and on to the floor inside. The mechanical room has it the worst because it is a small room with shotcrete coming in from all sides.  I will need to rent or hire a jack hammer to sort it out properly.

This shot is after spending an hour with a power chisel.

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I dug out several other areas for drains and to allow the radon pipe to exit…

But I still need to run the drains and radon pipes thru the rest of the structure, and I would guess that this lumpy surface will make it much harder to get the underfloor insulation and radiant floor tubes in place.  I am even a bit concerned about broken pieces of concrete tearing the vapor barrier.

I have a crew lined up to get in there to chip the rest of it out, but they are not available for another week or two.  And of course, this was not in the budget.

Waterproofing

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Posted on August 20, 2014 by

Before we can back-fill against the basement, we needed to clear the area, waterproof and put in the drain tile…  We also needed things like radon tubes and floor drains to exit the building.

My wife, Sherri, had to help a lot this week…  And as she puts it, “It wasn’t princess work!”  I did try to hire some people, especially when I realized I would have to carry down and place the 4 yards of pea stone by bucket, but it didn’t work out and we were on our own.

The video is here…

 

Stripping

I started with stripping the bracing away.  In most cases the wood was perfectly good with only a few screw holes.  I will get to use it all again on the second floor.  Actually, the site has only generated a couple bags of garbage and a box for recycling all summer, and that was mostly lunch trash dropped by the contractors working on the site.

I left the insulation on the side of the window well.  It was meant to be forming, but with an earth sheltered umbrella, it helps to insulate the earth where ever you can.

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We bought a power sprayer from home Depot (Graco Magnum X7), which worked pretty well.   We justified the purchase by reminding ourselves how much work it had been to paint the ceilings in our current house when we moved in.  This sprayer will come in handy when we do one last paint before we put our existing house on the market next spring.  As for the current task of spraying on the waterproofing, we saved a lot of time (and got better coverage) by not trying to roll the water proofing over that rough surface.  With only one sprayer, it was a one person job and Sherri took care of it.

As for the water proofing its self, we used ProteShield Elastomeric Waterproofing Sealer.    We actually applied it about 50% thicker than the directions specified.   The instructions said it would dry clear, but we were surprised that it appeared to “disappear” after just a few minutes (and faster on smoother sections of the wall).  It was like it wasn’t even there.

When we got the waterproofing inspected later, the building inspector was concerned about it.  He gave us a “partial” pass, and told us we could proceed at our own risk, but if the waterproofing doesn’t qualify, we will need to dig it up and do it over again.  We proceeded with the back-filling on faith in Home Depot and (later that evening) sent him this technical data sheet, which mentions that it is for above and below grade waterproofing of basements and foundations.  It even says to give it 48 hours to cure before back-filling, we gave it double that.  However, the inspector says it is missing a mention of some specific government tests that would qualify the waterproofing for use as below grade waterproofing.  The inspector is going to try and contact the company to see if they have this documentation, and if not, he is going to insist that we redo it.

Drain tile

I suppose drain tile used to be made of ceramic tiles curved into tubes and then fired.  In hispanic areas, I have seen them use the same tiles they use on the roofs.  These were placed end to end to help carry water away from foundations.  Now days, they are made of HDPE plastic that lasts forever.  Ours was also covered in a nylon sock to keep the sand from clogging it.

Actually, our site doesn’t even really need drain tile.  The sand just lets the water fall thru it, but the building code says we need it and that we need it to be covered in pea stone (an extra cost/hassle that shouldn’t be necessary for such a sandy site).

Another neighbor in the area told me that he put in the drain tile around his house to satisfy the inspection, but then didn’t actually run it to anywhere, since that part is not actually inspected.

I agree that these drains will probably never carry water, but I decided they should at least do something.  I am going to use them as earth tubes to carry fresh air into the house.  Sherri doesn’t like the idea of carrying fresh air thru corrugated pipes because water can sit in them and cause problems (mold, humidity)…  But I also know of many success stories.  I wanted to try it out and I can always seal them up if it doesn’t work out.

The first day that we laid the drain tile, the battery died in the camera, so you don’t see how many hours it took me to get it all sloping just right.

The big hassle on the second day (Saturday) was carrying all that pea stone down into the “pit”, bucket by bucket.  We didn’t make our Saturday night deadline.  The inspector is only available for a few slots each week, so if we missed Monday for the pre-backfill inspection, we would need to put off the back-filling and schedule the inspector for Wednesday…

That was the the day my sister was coming into town…  We would need to come back and finish up then.

Insulation

You can’t see it in the video because Nick and I were working on the other side of the basement.  We initially hoped that the waterproofing would be sticky enough to “glue” it, but it was not sticky at all.  So we waited for the waterproofing to dry (2 hours cure time), and then tried to glue 2 inch thick Foamular 250 to the walls using “Liquid Nails“…  That didn’t work out at all because we couldn’t keep the stiff foam pressed against the curved wall long enough for the liquid nails to dry.  We decided to add the insulation as we back-filled…  The dirt will hold it in place very well.

Shotcrete!

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Posted on August 18, 2014 by

I have been too busy lately to put together a post.  However, about a week ago, I did manage this video of final shotcrete prep:

Then we got the shotcrete in and I started on a detailed video with close ups, etc. but it was too long (10 minutes).  I didn’t want to cut all the good stuff out, so I quickly put together a second shorter version this evening (with the promise of releasing the more detailed version eventually).

As with every experience, I learned a lot and will write up more details later.  The main thing is that I should have spent less time worrying about how flat the lath lays and more time tying the lath to the rebar.  I missed tying a few sections and they pushed out like an overstuffed pillow (except with concrete, so less fun).  I also learned that there is a front and back to metal lath.  It catches shotcrete better if it is oriented correctly.  The shotcrete guys really liked the steel studs, but they had me remove the 2″ wide steel strap after the first “lift” of shotcrete was in place. The wider strap was getting in the way and creating a shotcrete “shadow).  I’ll put a structural page together on this subject eventually.

Here is a pic of the shotcrete going in.  The nozzle man in the back is shooting and the finishers have to follow fairly closely behind before the concrete hardens.  The smokey air is like aerosol concrete mist.

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This next one is how they handled a 135 degree corner…  Sharp on the outside, nice rounded (and over 1 ft thick) on the inside.

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As for the final look of the shotcrete, it is a bit lumpier than I expected.  The optimist in me would call it “organic”.  I expected it to look like a pool (pretty smooth). The shotcrete guys usually make pools and they said they it will, after it gets plastered. I think I will need to grind off some of the uglier lumps first.

Here is a cross section of my the shotcrete around mechanical room.  They had to interrupt the spray so we could still get in and out (no doors in a basement wall).  some of the thickness variation was sorted out in later lifts.

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The cost was also higher than expected. The basement was expected to be just over 40 yards of concrete in the walls.  I had originally been told 1 day with 4 guys. Instead, 8 guys worked for nearly 2 days… I expected 6″ thick and got mostly 8″ thick, so my concrete volume was higher. There was also much more waste thru the lath than expected.  The concrete price had also gone up (from 84$ to 91$ per yard.) Things were in motion, and the overall cost is still fairly low, so I just rode it out.

In the end, I bought 40 yards the first day and 18 yards the second day (but we dumped several yards each day and ended the job with lots of concrete still in the mixing truck).  I still paid less (including steel, rebar, etc.) than I would have for a poured basement with straight walls.  But, I guess the poured basement would be smooth finished, and I still have a lot of plastering to do.  My shotcrete basement is more than three times stronger than any poured basement.

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