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WILL1E
Moderator
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# Posted: 7 Jun 2022 07:50am - Edited by: WILL1E
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I'm having alot of regrets about not using a 3rd built up beam down the center of my cabin joist. Structurally everything is fine and sized appropriately, i just hate that i can feel a bounce anytime someone walks in the center area of the cabin, especially my teenager and his buddies as they seem to walk around like a pack of horses.
The cabin is 16' wide and 32' long. You will see in early phase construction photo below there isn't much room underneath. So what would be my best approach for getting something under there just to take the bounce out of the floor?
I was possibly thinking i could do some precast blocks or pads with one of these between the concrete and the beam. This way i can adjust things as needed.
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WILL1E
Moderator
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# Posted: 7 Jun 2022 07:56am
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Or something like these pads.
I realize that if i put the concrete pads on the surface i will need to do some adjusting throughout the seasons, but if it gets rid of the bounce it would be worth it.
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gcrank1
Member
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# Posted: 7 Jun 2022 08:35am - Edited by: gcrank1
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So, how long before the heavy stompers arent going to be pretty much always there; ie, is it not an issue otherwise?
Am I right suspecting the bounce is about the middle of the main living area?
If I were you, Id find a way to drag a 'silo block' ('cause I have them) under that spot and use a hydraulic jack c/w a under-joist block to get some up pressure there and see what it does.
Fwiw, Harbor Freight has had h-jacks. Mine have worked well.
If that works you can do blocking to replace the jack.
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WILL1E
Moderator
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# Posted: 7 Jun 2022 08:43am
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Well he's only 15 so he'll be around for a couple more years. Plus neither him nor I are small guys. He is 6'3 200lbs and i'm 6'5 260. So i'm sure once the wife starts sleeping in the cabin, she will feel me walking around.
Yes, the centerline of the 16' direction is the worse.
I'm thinking if I get a couple of these sunk flush with the gravel, then add these adjustable bases on top to support a doubled 2x10 i should be golden.
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paulz
Member
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# Posted: 7 Jun 2022 09:40am - Edited by: paulz
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Quoting: gcrank1 If I were you, Id find a way to drag a 'silo block' ('cause I have them) under that spot and use a hydraulic jack c/w a under-joist block to get some up pressure there and see what it does.
I have a raised walkway on one side of the cabin, a ledger on the cabin wall and a beam going down the other side, sitting on two pier blocks. I've had to level it a couple of times as the blocks settled, I just jack the beam up to level and add a wood shim in, let it down.
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gcrank1
Member
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# Posted: 7 Jun 2022 09:54am
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Dont overthink it Will, and it doesnt have to be pretty for a Better Cabins and Cottages photo shoot, does it?
Imo, the bigger the pad the better, thats why I like the silo blocks. My '83-84 build, 12x24 with a 12x12 loft, Swiss chalet look cabin (way bigger/heavier than I originally planed) was on s-blocks with nowhere near the ground prep you did (though it was on a sand & gravel knob of a hill in the woods). In over 30yrs I really only had to jack one spot when the centered door on the long side started to drag a bit.
S-block
Reg cement block
Various thinner landscaping blocks
Treated lumber shims as needed
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WILL1E
Moderator
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# Posted: 7 Jun 2022 11:37am
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Quoting: gcrank1 it doesnt have to be pretty for a Better Cabins and Cottages photo shoot
No, but at the same time i don't want it to look shabby either. I need to put a beam of some sorts down the length of the cabin and If i'm gonna crawl under there to scrape the ground and put some blocks in and put a beam in, i might as well make the "jacks" look official while still giving me the adjustability in the event things settle. So really the only thing that's up for debate or adding/subtracting cost is what i do for the "jack" part.
Another option might be an octagon footing pad, with a deck block on top of it followed by one of these brackets
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travellerw
Member
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# Posted: 7 Jun 2022 12:09pm
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I will offer another option instead of a beam.
We did the whole double floor thing in our cabin! 3/4 OSB, then 2" foam, then 5/8 OSB. We originally did it for insulation, but its had the added benefit of making the floor super solid. It pretty much made the floor like a laminated boat deck. We screwed through all layers and into the joists with 4" screws, however if I did it again I would use a small amount of thinset at each of the layers to make a true laminated floor (then no screws). Pretty sure that would make a floor with a stiffness like a concrete pad.
It will cost more, but you get the added benefit of an insulated floor. Its worked out so well on our that I'm not going to bother skirting the cabin. Even at -25C the floor is warm enough to walk on with slippers.
However, the beam option you posted would work well too. Using adjustable brackets ensures that you can adjust if the center beam heaves or sinks (the biggest problem with 3 beams). The precast blocks will have more then enough strength for that (no real load other than just trying to take the bounce out).
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Aklogcabin
Member
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# Posted: 7 Jun 2022 02:24pm
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If I may ask. Why did you go with just 2 floor support beams so far apart from the start ? From the picture it looks like you're spanning 14 foot or so with the walls sitting on a cantilevered edge also instead of over the foundation pilings. Your dealing with a tremendous amount of weight.
At 32' long your going to need more support in the middle of any beam structure spanning the length.
Thinking you may be able to deal with some of the worst bounce by focusing on the worst spots. Something like individual supports. Like a 4x6x8 used directly under the living room floor area.
In my opinion spanning this far is too far. Folks seem to worry about the middle support of the floor frost heaving. And not do them. But it will stay dry and not heave if done correctly.
Having a bouncy floor can be bothersome and as big as you are I suspect that you can feel you walking around through the whole cabin. And will be there until you add some more support.
Good luck. Your cabin looks very nice. How did the pellet stove work out for you ?
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curious
Member
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# Posted: 7 Jun 2022 04:42pm
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Curious here, what size are the joists and their OC spacing?
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snobdds
Member
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# Posted: 7 Jun 2022 04:46pm
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Quoting: Aklogcabin If I may ask. Why did you go with just 2 floor support beams so far apart from the start ?
There use to be a guy on here that advocated for a skid foundation on two beams.
If he only knew the path he was leading people down.
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paulz
Member
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# Posted: 7 Jun 2022 04:59pm
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I have two beams, but only 12' wide with 1' cantilever. No bounce. My joist are also on 1' centers.
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Brettny
Member
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# Posted: 7 Jun 2022 05:37pm
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Yup no one ever said.."I wish I didnt build this foundation so good" it's always the other way around.
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spencerin
Member
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# Posted: 8 Jun 2022 12:32am - Edited by: spencerin
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Can you not replicate what you have for the 2 existing beams down the middle so it looks original and uniform, which is what you want? Seems like there's enough room to get around on your back under there.
Also like the idea of adding a limited-span support just in the center. Less work and more flexibility in construction since it won't be visible.
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gcrank1
Member
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# Posted: 8 Jun 2022 09:20am
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The advantages I see to that are:
It is quick to do
It is inexpensive
It will let you know within a matter of hours (at max) if it addresses the issue
You can always upgrade it
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WILL1E
Moderator
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# Posted: 10 Jun 2022 02:57pm
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They are tripled up 2x10 breams with 2x10 joist @ 16" OC. The cantilevers cannot exceed the height of the joist, so i think there's only like 9" of overhang.
So far i'm the only one that notices the bounce, but it's enough that it bothers me so it needs to be dealt with. Replicating what i did for the other beams will be extremely difficult hence why i didn't list it as an option. Plus, if heaving ever happens in the middle it will be difficult to adjust.
I ordered up those brackets in the photo above. I'll do a doubled up 2x10, those brackets, deck block and then a footer pad that fits the deck block.
I think i'll eventually skirt the cabin to keep leaves and stuff from blowing under there, so i'm not terribly worried about looks.
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travellerw
Member
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# Posted: 10 Jun 2022 05:04pm
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Quoting: WILL1E So far i'm the only one that notices the bounce, but it's enough that it bothers me so it needs to be dealt with. Replicating what i did for the other beams will be extremely difficult hence why i didn't list it as an option. Plus, if heaving ever happens in the middle it will be difficult to adjust. I ordered up those brackets in the photo above. I'll do a doubled up 2x10, those brackets, deck block and then a footer pad that fits the deck block. I think i'll eventually skirt the cabin to keep leaves and stuff from blowing under there, so i'm not terribly worried about looks.
Yup.. I was actually surprised when I saw you post. Before we did the double floor thing I had my son jump up and down and I could detect bounce but it was minor (I think my deck here in the city has more bounce). Everyone is individual though, what bothers some doesn't bother others.
I think you are onto a good solution to take the bounce out while still having no risk of the "third support hump syndrome"
As to skirting. I had planned to use "Coroplast". If you buy it from a plastics supplier its cheap, light and available in pretty much any color. RV manufacturers use it to enclose underbellies on some RVs. I was going to use 2 layers, then caulk the channels at the top to provide a "dead air" insulation. It wouldn't be much insulation, similar to "bubble-foil" in R value. I was going to bury the other end in a shallow channel to discourage animal entry (skunks are bad here, they will go under any skirted building and make a nest). You will want to make sure you make some "windows" that you can open in the spring/summer/fall to make sure you don't get moisture problems under there.
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gcrank1
Member
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# Posted: 11 Jun 2022 06:45pm
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Will, you are right to address it now. It aint gonna get better over time (trust me, btdt, it just doesnt happen  ). And time passes too quickly, we get less able/too busy to get to it.
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