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"It's just like Lego!"

Nelliekins

Entry posted by Nelliekins

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So, our slab is down, starter bars set ready for our walls, lovely. Time for some ICF...

 

Nope - more prep work to do first, apparently. The boss from Logix UK came up a couple of weeks prior and gave us some on-site training. "It's just like Lego!", exclaimed I. To be fair, it did seem really simple. I learnt just enough on the first day of training to be dangerous.

 

The basement wall blocks arrived on a pallet truck. Except it was only some of the blocks - they'd forgotten to send the internal wall blocks, and only sent flat panels for us to make most of the blocks ourselves. No biggie - it only took a hammer and 60 seconds of effort to assemble each of the blocks. Shame there were a couple of hundred...

 

So, getting the blocks into our hole was entertaining, though - we started off hand-balling them down a ladder! After we had a few down, we started looking to set the first course. We bolted a set of aluminium track around the perimeter - the track is 72mm outer width and 70mm inner width, which is exactly the same width as the EPS panels for the basement. It came in 3m lengths, so with 16 lengths bolted down, we had a perfect perimeter into which the blocks would sit.

 

Here's the first block going in for a trial fit:

 

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Oh, the sharper-eyed among you may have noticed there is what looks like a channel/groove set into the slab, just outside of the starter bars. That was cast into the slab (using lengths of 20mm electrical ducting) to take the Sika swellable water-stop bar, and it was a perfect fit... shame we didn't think to set it into the channel until after we had placed the first course of blocks! DOH!

 

Anyway, the block fit perfectly, so we carried on setting out the entire first course, then realised our mistake and put the swellable bar into its channel (stuck down with some horrendous swellable mastic provided by Sika, that took best part of a week to wash off my hands - oops!)

 

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So far, so good. But hand-balling blocks or panels down a ladder wasn't cutting it, given we needed to get several hundred blocks down... so we made a slide! The pairs of timbers were set so that the webs on individual panels fit perfectly between the 2 timbers, keeping them level and preventing them from flying off.

 

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Before we knew it, a good chunk of the basement walls were up. Next day, and we continued apace. By the end of the week, most of the basement walls were up and it was time to call it a day. The man from Logix had suggested we cover the tops of the walls temporarily to prevent the swellable bar from getting too wet, so we used the ICF cavity closers - after all, we were relatively sheltered from the wind, so they shouldn't go anywhere...

 

Next day onsite was the following week, and a surprise arrived - the internal wall blocks! Not only that, but the boss of Logix UK arrived with them, to carry on our on-site training...

 

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Since he had brought his internal wall blocks and the bracing system with him, I figured he could help with the internal walls. Now, if ever there was a mistake...

 

I don't know if anyone paid attention to the design of the house, but there is this lightwell out the back of the basement. It's designed to serve 3 purposes:

 

  1. To provide a secondary means of escape, in case the basement stairs are on fire (there's a window being put into the back wall)
  2. To provide a place to put the rainwater harvesting tank (I'm a notorious cheapskate, and I had noticed that above-ground tanks cost a fraction of the below-ground tanks... ergo, with a lightwell - covered by a deck at ground level - I could house a giant above-ground tank, but keep it out of sight!
  3. To provide somewhere to site our perimeter drainage sump (we were going to backfill around the basement walls, with a french drain that flowed into the sump chamber in the lightwell, so that it could be pumped away, and remove hydrostatic pressure from the basement walls

 

"So why is he banging on about the lightwell?" I hear you ask. Good question.

 

Internal T-walls with Logix are made with dedicated T-shaped blocks...in the US and Canada. Over in Blighty, they're not allowed to make those blocks (because Logix UK is a licensing outfit, with very limited production rights), so you have a choice of waiting up to 6 weeks for them to be shipped across the Atlantic, or bodge the T-wall by simply cutting pockets out of the side walls to allow concrete to flow between side and cross walls, and you can put rebar L bars into the wall to tie it all together. Which option do you think I picked?

 

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If you look carefully, you can see the pockets cut out of the side walls, and the steel rebar hanging out of the side wall to tie the side and cross walls together.

 

Which would be fine, except this is the external wall of the house. The area to the left of that wall is the basement, and the area to the right of that wall is the lightwell.

 

Now here's a little test for the brighter students among you... what's wrong with this arrangement? Answer in the next blog post! ?

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Nelliekins
1 hour ago, jamiehamy said:

It's not water tight?!

 

Bingo! ? We put a swellable bar under the wall as per everywhere in the basement, but ignored the vertical joint. Then, when it rained a lot and the lightwell filled up a bit, we were getting water into the basement... But of course we didn't know this until much later in the build, when we thought we were watertight... ?

 

1 hour ago, jamiehamy said:

Plyd is the join strong enough should the pump fail and water gather? 

 

It's plenty strong enough, because there are solid ICF walls above as well that are built as external corners over the joints. 

 

Plus the lateral stress on that wall is nil. It's shielded from the weather by a deck over (or will be!). Plus, there are 7 courses of blocks, each with 5" diameter concrete "plugs" with 12mm rebar going through them and then bending in alternating directions once they are in the side wall. Then there are the 22 starter bars set into the slab with liquid concrete anchor. The wall is way stronger than a typical masonry wall above ground, too - the concrete cubed at C68 on the basement mix.

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ProDave
5 minutes ago, Tennentslager said:

Sorry don’t get it...the external wall is continuous so no leaks there 

how can an internal wall cause it to leak?

If I am understanding it, it is because part of the basement is open, with no roof (a deck later?) to allow a free standing "underground" water tank.  So that bit can fill up like a pond if I am understanding it when it rains, and water got in through what had been built as an "internal" wall detail.

 

Personally I would not be happy with that sort of underground unroofed area.

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jamiehamy

Hmmm, so the water inside the light well will come from... Where? If from the sky only, then is there an option to put some form of roof? Or if from the ground through and inlet, which if I read correctly is right, then there will be tanking options available I think. It's actuary something I need to do for our garage before we backfill. I didn't out in a water bar for various reasons, and will want to tank externally, but the main challenge is finding a reliable tanking method compatible with our XPS ICF walls. Paint of solutions from the likes of Alchimica won't work, so will need a combination. That's still an option for you I would imagine? With close attention to detail and care AFTER the install, no reason you can't get water tight. 

 

My comments on strength of wall were based on a worst case scenario where the pump failed (whilst in holiday) and the lightwell filled substantially. I don't doubt its likely to be strong enough but might be worth doing some calcs to be sure? Worst case, which is a valid scanario, there could be 3m water in there with sfonfococant lateral/hydrostatic pressure. 

 

I'll be completely honest, were it me (which in a way it is because of my backfilled semi undergoing garage) I'd consider tanking the basement from the inside too (if you're not already planning) . You are reliant in the water bar working 100%. 

 

I know its easy for me to say but I think it's worth suggesting and considering? 

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mvincentd
10 hours ago, jamiehamy said:

You are reliant in the water bar working 100%. 

so make sure the design ensures the water bar is fully encased....ie doesn't terminate at top of wall to 'free air' or a detail that doesn't keep it in compression.

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