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Small Cabin Forum / Cabin Construction / Radiant heat and Leveling an unlevel/uneven floor
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# Posted: 6 Jul 2022 11:15

Hello Again Fellow Cabin Junkies!!!!

I've got another wild idea here and would love some input or to know if its maybe not so wild of an idea LOL...

The floor in my cabin is atrociously unlevel in varying directions. Jacking up the floor structure isn't a viable option and the floor is currently properly supported underneath so the unlevel isn't cause for concern other than personal grievances/personal comfort.

I'd also like to note that in the future, I want to try and add underfloor hot water radiant heat (pex tubes). Of course, pending finances and time.

That said, I was YouTubing for ideas on how to level a very unlevel floor (without jacking up the floor) and came across this video (if anyone is interested): I love this guy's method of leveling the floor. I know you can cut raked pieces of boards but never thought to use the screw method he uses. Assuming I cut sleepers on a rake and level out the floor (then top off with new plywood), there will be voids between the top of the sleeper and the original floor, up to 2" in some spots.

If I then do decide to add radiant heat in the future, those empty voids will really affect the way the floor heating works, in fact it probably won't work very well unless I DO fill the voids. Obviously foam insulation isn't a good idea as that will only slow the heat transfer. Then I remembered reading somewhere in a heating forum to fill the voids with sand or cement as the sand/cement will conduct the heat through. Sounds kind of like a good idea...???

Has anyone done something as such? The idea is that the sand will come in contact with the original sub floor and conduct the heat from the sub floor (in the future when I install hot water tubes below) and carry it up to the leveled finished floor. Ideally, now would be the time to install the pex tubing in the voids but I really don't have the time, the money for the tubing and the design of the radiant system is not complete yet so i'd be installing tubing "blindly". The radiant heat project probably isn't going to happen for a few years amyhow if at all. Sand is cheap and can be done now. I currently have fin/tub hot water baseboard I plan to keep for the time being but if I can fill the voids now with the intent of adding radiant heat down the road, this sounds like a good idea to me but also another one of my crazy ideas.


# Posted: 6 Jul 2022 11:32

Seems like a tremendous amount of work. I have another idea which is food for thought. Cover it with plastic, pour concrete with wire in it and your PEX lines while using leveling
strips to screed out the concrete. Then install your flooring on the concrete. It's kind of the same idea as setting a plastic tub in mortar on a wood sub-floor. I just bought an old house and the entire floor under the second floor bathroom is poured concrete. I guess that's the way they used to do it when they laid tile, so it would not
shift and crack. We had a plumber re-pipe the whole house and he discovered it when he had to install a new line to a toilet because access to the old hole was blocked by a drain pipe. He had to use a hammer drill to drill up and through the floor from below.

# Posted: 7 Jul 2022 11:31

How did it get so un level if its properly supported underneath? That dosnt make sence to me unless it was built with varying sizes of wood.

# Posted: 7 Jul 2022 12:49 - Edited by: jsahara24


# Posted: 7 Jul 2022 14:05

I am skeptical about the idea of doing something on top to make a level floor out of what you describe. If jacking is not possible how can you be certain the foundation can be described as "properly supported underneath"?

PEX is sometimes installed for radiant heating on top of an existing floor by pouring a gypcrete mixture over the PEX that is secured in the desired pattern. Not ordinary concrete. Gypcrete is much lighter and is softer, easier to crack.

The whole idea sounds a bit hare-brained and likely to end up with new problems, even if some old, existing issues are resolved.

# Posted: 7 Jul 2022 16:16

ok ok, i know my ideas are hair-brained that's why there are support groups :p and anyone else just doesn't get the appeal to an old log cabin that needs a lot of love and creative solutions to bring her back to life without spending 10x the cost of the property value to do so!

why did the floor get so unlevel? well over time the last 100 years (ca.1922) the field stone foundation settled in one of the corners. Then it looks like the spikes they used to nail the rim joists into the bottom logs rusted away in a few spots. Rust you say? That's obviously concerning but no, the logs aren't rotten or deteriorated and I don't see any signs of water leaking in. I can only make the guess that the builders used "wet" logs and ungalvanized spikes. A previous owner went through and built up the inside walls of the basement foundation with footings, cinder block walls, lally columns, etc. and supported the rim joists on said block; they never bothered to jack up the floor and level it. I did have a structural engineer/architect look at it as well which is why I am not overly concerned with the safety of the floor structure. I also planned on installing some kind of structural lag bolt (TimberLock i believe is the brand the architect recommended) to better secure the rim joist to the bottom log.

I suppose if I wanted to get even crazier I could try to jack up the floor but I feel that will only make things worse hence why cutting sleeper strips was thought to be a better alternative. My initial plan was to just live with the sloping/wavy floors but as i come across new idea, I like to explore.

As for the heat, I was considering installing it on the underside as that could be retrofitted down the road when I have a few more funds to do so. It would also be relatively easy stapling up pex/aluminum heatsinks to the underside and plumbing it to the boiler at that time. Open air gap would defeat the point of underfloor radiant which is which is why I considered sand or something of the sort. I've done a lot of tile floors in the past and we use to wire mesh and cement over top. I know today there's better options. Oh and I need to have someone do a heat/loss anaylsis and properly design the heat loop setup for the radiant before anything if I were to install on top of the subfloor. By time I have that done, I'll have the floor leveled and ready to be installed.

Thanks for the Gypcrete idea. That might be a viable option; at least at alternative to explore.

Thanks for your input. I appreciate every bit of information I can get.


# Posted: 7 Jul 2022 16:52 - Edited by: gcrank1

My circa 1875ish home was the local one room school house. It was moved 2x to the current poured foundation. 1st time from the original location 1/4 mi. away to the south side of our 1.3 ac. then again to the north side after the foundation was done.
It too has 'wavey floors'. 35ish years ago I did simple laser level shots to figure out where my high and low corners were and jacked/shimmed some and poured mortar in the kitchen and bathroom after underlayment. In retrospect I should have cut the old floor out with a carbide circ-saw blade, sistered level joists to the originals and replaced the deck. But it was our live in home, not easily done while trying to live in and make a living while rebuilding!
Our 10yr old 'new' cabin is a glorified shack by the prev owner and needs the same . At 69 I doubt I have it in me..... But it would be the right thing to do.

# Posted: 8 Jul 2022 09:32

Sounds like you have a plan. I'm glad to see these older cabins get a little tlc. They can still provide you with a lot of enjoyment. And having a little tilt in the floor is not uncommon. That doesn't necessarily make it unsafe.
Way back when I installed flooring for a job we used a product, mix-all maybe. Was in a green box. A powder that mixes with water and can be spread out with a trawl. To fill the cracks in the floor or plywood seams. And to level out areas that needed it. You can mix it a little thin to give you more working time. Sets up hard in a half hour and can be sanded if needed.
Good luck n stay positive, have fun, you'll get it

# Posted: 8 Jul 2022 10:24

I have used that, or a product like it. It was kind of expensive but considering it was intended for just seam fill it was ok, imo it would be too costly for a large area.
When I did my shower unit at home it called for a 'mortar' base beneath the shower base. The lumber yard had a bagged product suitable at a fraction of the cost, probably that light-weight version previously mentioned. Mixed toward soupy it was mostly self-leveling with only a little 'pushing' via trowel.
That said, Im no 'crete guy and wouldnt want to do a large area. Shims, sistered joists, new subfloor, etc; wood I can work with and at my pace (slow), suits me better.

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