Floating basement Walls?????

[MitchP]

Looking for some advice with my basement bathroom. I have just finished framing the walls. I have floated them with a gap on the bottom, leaving a gap between the treated plate attached to the cement and the bottom plate of the wall. I understand why this is done and have noticed that my floor has moved since I have built my house in 2012. The question Is I am ready to frame the tub enclosure in. I was going to build the enclosure the same way as the other bathroom walls but am now wondering what will happen when the floor moves that the tub is sitting on. Won't this put pressure on the tub that is secured to the floating walls???


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[CNP]

I have a new house, none of the basement walls are floated. Are you in an area where soils require this? Just curious...

[Newview01]

I have never heard of the practice of floating basement walls.

[Trochu]

Yes, if the tub is sitting on the floor, the walls are hanging and attached to the tub, it will put pressure on them if the floor moves. Check your local building code of course, but a few ways around this are to gap that particular wall at the top (make sure its not fixed to other walls in a matter that will restricting movement), install a free standing tub, or hope no more movement will occur. I don't think many basement walls are floating in Alberta. Did your floor move up or down?

[Passthru]

We don't build floating walls in the basement at work. Build these all the time. Wouldn't finished drywall or the baseboards get messed up if there was movement after the fact? Plus the tub. Make it tight

[58thecat]

High river...make sure your tub has an outboard on it
Basement floats....build on high ground?
Sorry couldn't resist.

[^v^Tinda wolf^v^]

I'm no carpenter but I would think it would create all sorts of issues. I read up on this when I finished my basement and if I remember correctly it was a lot of people in the states that were doing this because of more sand content under the foundations. I would drive door shims under it before going any further IMO

[zims23]

I am from the Regina area. Everyone there floats the basement walls. The gumbo soil moves the floor up and down. I would float the wall at the top instead of the bottom.

[MitchP]

Yes it's common practice here in southern Saskatchewan. I found out why as my floor has moved already, hopefully no more. It's caused by the soil type in my case solid clay. Sand seems to be the best type of soil for this issue as water drains through it quickly. The clay which was once dry has got wet which makes it expand and has hydraulic properties. I have taken care of a few issues outside my house and have had an engineer look at it. He explained the issue to me and I'm hoping I never have to worry about it in the future. The problem with just framing the tub enclosure floating at the top is that the walls of it would have to be attached to the walls of the bathroom which are floating at the bottom. The drywall would crack right away I would think. If there is anyone out there that has a solution I would greatly appreciate the advice.


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[CantThinkOfAName]

Originally Posted by MitchP

Yes it's common practice here in southern Saskatchewan. I found out why as my floor has moved already, hopefully no more. It's caused by the soil type in my case solid clay. Sand seems to be the best type of soil for this issue as water drains through it quickly. The clay which was once dry has got wet which makes it expand and has hydraulic properties.

Isn't Edmonton soil clay-based as well? Too the point when an auger stopped drilling on an fence-hole I filled the hole with water to help soften it... and the water never did drain out. But I don't hear anybody making free-floating basement walls. Or different type of clay?

[MitchP]

I would think if you looked into it free floating a basement wall is either common practice if not code.


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[MBL]

Not common in alberta. If it's such a common practice there maybe try asking a local contractor how they do it.

[^v^Tinda wolf^v^]

I guess there are several factors left out that we don't know such as location of the bathroom and how the house was designed. My place told me it wouldn't be an issue but had a couple concerns due to cracking in the cement which is now sealed and sat for a year while I watched what else moved through the seasons on my bi level. Someone here simplified it all by suggesting gapping to top but would the top then crack out if it were moving enough ? Possibly a floating sealing for such an issue

[wildwoods]

Framed a lot of buildings myself. NEVER have we floated the walls off the concrete. Sometimes there is a small gap between the top plate and the floor above due to concrete not being consistent height. Also, a lot of commercial projects we frame are supported on bearing walls right down to the basement concrete. Floating would not work at all in that application.

I've seen many frozen basements in the wintertime heave BEFORE concrete was poured due to frost. Once it's poured and heated, it won't move much if at all.
Very strange.
PM me if you want a phonecall to discuss...

[Digger1]

I've been digging basements on and off for about 29 years, and if the subgrade had that much issue with load bearing, I don't know an engineer in Alberta who'd pass it. I did the Telus Spark science centre in Calgary in 2010, and being that it's built on a landfill, the floors are completely self supporting, 30 cm thick with 60 cm thick around the support pilings. Never hearn of floating on purpose.

[omega50]

Very common practice in Manitoba- with the Gumbo soil

[MitchP]

Wow I guess I took it for granted that this was the Norm. I renovated an older house in Redcliff and left the gap at the top. Every local carpenter out here has seems to have gone to hanging them from the joists. I'll ask the local guys what they do in the bathrooms.


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[MitchP]

Originally Posted by MitchP

Wow I guess I took it for granted that this was the Norm. I renovated an older house in Redcliff and left the gap at the top. Every local carpenter out here has seems to have gone to hanging them from the joists. I'll ask the local guys what they do in the bathrooms.


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[220swifty]

Originally Posted by MitchP

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3" of play!? Holy cripes. If you told me you expected my floor to move that much, I'd tell you I wasn't buying the house. If you can expect that kind of movement out of your floor slab, how do you have any faith in your footings? Do they drive piles down deep in these parts to ensure a solid foundation, or does the whole building move?

[HyperMOA]

Originally Posted by 220swifty

3" of play!? Holy cripes. If you told me you expected my floor to move that much, I'd tell you I wasn't buying the house. If you can expect that kind of movement out of your floor slab, how do you have any faith in your footings? Do they drive piles down deep in these parts to ensure a solid foundation, or does the whole building move?

I believe it is code in the Regina area actually. I have never seen 3" however. Its always 1.5". Conveniently the same gap as 2x4 "shims" which are knocked out once the walls are secured to the floor joists and in phase with the lower plate. Coincidence?

[MitchP]

Yeah I found that pic on a thread from Colorado. I left 1.5" on mine.


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[MR.K]

I built a slab on grade house (no bsmt or crawl space)
Treated sill plate is concrete nailed to floor and top of walls to trussess
Almost 3 years old and no movement
That kinda movement would be destructive to my in floor radiant heat

[Grizzly Adams]

Originally Posted by 220swifty

3" of play!? Holy cripes. If you told me you expected my floor to move that much, I'd tell you I wasn't buying the house. If you can expect that kind of movement out of your floor slab, how do you have any faith in your footings? Do they drive piles down deep in these parts to ensure a solid foundation, or does the whole building move?

Properly constructed foundations and floor should move very little. Floor not cracked all to Hell ?

Grizz

[220swifty]

Originally Posted by Grizzly Adams

Properly constructed foundations and floor should move very little. Floor not cracked all to Hell ?

Grizz

Yep. This is what I'm wondering too. This discussion has done nothing but raise questions in my simple framer's mind.

[Trochu]

Originally Posted by 220swifty

Yep. This is what I'm wondering too. This discussion has done nothing but raise questions in my simple framer's mind.

Hopefully I can answer/clarify some of them for you, and clear up other comments I have seen in this thread. This is a complicated subject if you want it to be though, and there will likely still be some questions.

Some clay is high plastic, meaning, when it gets wet it swells and when it dries it shrinks. The only way to eliminate movement of high plastic soil is to manage the moisture, either keep it saturated, keep it dry, or maintain the moisture content. High plastic soil isn't an issue in a large part of the province, but it is common is some locations, Grande Prairie for example. I believe it was the Baker Hughes shop in GP along Hwy 2 that was condemned and tore down due to high plastic clay. As stated, most homes in Alberta aren't affected. Those that are deal with it in a number of ways. The most utilized method is to install weeping tile around the perimeter, clay cap at the top, slope away from the house, and the subgrade eventually drys out/maintains its moisture content. End result, no movement. Others deal with it in a variety of ways, deeper footings, no basement, piles, designed to allow some movement, more rebar, etc. The reason a slab might move relative to the house due to high plastic clays is that the slab is typically lighter, and concentrations of water via leaking floor drains, pipes, etc. For the majority of Alberta though, slab movement isn't related to high plastic clays, it due to settlement.

[MugEye]

Originally Posted by Trochu

Hopefully I can answer/clarify some of them for you, and clear up other comments I have seen in this thread. This is a complicated subject if you want it to be though, and there will likely still be some questions.



Some clay is high plastic, meaning, when it gets wet it swells and when it dries it shrinks. The only way to eliminate movement of high plastic soil is to manage the moisture, either keep it saturated, keep it dry, or maintain the moisture content. High plastic soil isn't an issue in a large part of the province, but it is common is some locations, Grande Prairie for example. I believe it was the Baker Hughes shop in GP along Hwy 2 that was condemned and tore down due to high plastic clay. As stated, most homes in Alberta aren't affected. Those that are deal with it in a number of ways. The most utilized method is to install weeping tile around the perimeter, clay cap at the top, slope away from the house, and the subgrade eventually drys out/maintains its moisture content. End result, no movement. Others deal with it in a variety of ways, deeper footings, no basement, piles, designed to allow some movement, more rebar, etc. The reason a slab might move relative to the house due to high plastic clays is that the slab is typically lighter, and concentrations of water via leaking floor drains, pipes, etc. For the majority of Alberta though, slab movement isn't related to high plastic clays, it due to settlement.

Ok that makes good cents . If been building now for 16 years and never herd of floating walls . But yes moisture under a slab is normally not a good thing. Weeping tile is always used. So in these high plastic clays I imagine the telepost and load-bearing walls are supported by a non conventional type of footing . Know what you got for a house or build site and build accordingly

[Grizzly Adams]

The most utilized method is to install weeping tile around the perimeter, clay cap at the top, slope away from the house, and the subgrade eventually drys out/maintains its moisture content. End result, no movement.

This is just considered good building practice anywhere I've ever worked.

Grizz

[MitchP]

Very good advice Grizz! I had the weeping tile in place but did the clay cap just below grade a little too late. All done now including a layer of bentonite below grade. I am hoping my issues are over and like you say the subgrade should eventually dry out.


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