floor support question

[Capt_Cully]

Area I will be bracing is in a crawl space portion of our basement. Easy access, about 3-4 feet high. The floor, however, is composed of fairly well packed, albeit loose rock crush. The pieces are about 1cm each.

I braced my old tank using pressure treated 6x6s under the joists. Planning to do the same.

Question is, what would you recommend for placing the support poles on, as they would likely sink over time into the rock floor?

Thanks

 

[fatrip]

I would dig a cylindrical hole and pore cement as a base. Pretty easy and it shouldn't take but a few hours on the weekend. This would give you the most sturdy base as well.

 

[Capt_Cully]

Lets just say, for arguments sake, the actual crush is under heavy plastic as part of a radon evacuation system. I'm not discounting your suggestion Vince, I'm looking for additional options as well. The guys are coming in about 10 days to seal it. Not sure I'll get the time to dig and fill.

Could I use pressure treated 6x6s on the bottom to increase surface area? Would they sink over time too? How about patio paver slabs or something like that??

 

[mr.maroonsalty]

Tough question to answer without seeing things like dimension of floor joists and the positioning of the tank. The crawl space isn't heated, so anything needing support needs to have a footing that goes under the frost line for it not to move around with the seasons. I don't know how deep that would have to be in a crawl space application, it may still be 4'. There are other ways to increase the load capacity with out using posts.

 

[Jacwil]

Double up the joist...

...I'm waiting to hear back from a cpl buddies from our old framing crew, but I think doubling the joist will help distribute the weight.

How big are the the joist in there now Mark and on what centers?

 

[Capt_Cully]

I have to wait til my wife gets home to measure. Pretty sure they're 2x10s. Not sure of spacing.

 

[Jacwil]

Ok...another idea is pavers and some jacks. Not sure how do-able it is and others can chime in but this would allow you to get under there and adjust when needed.

 

[Capt_Cully]

Ok...another idea is pavers and some jacks. Not sure how do-able it is and others can chime in but this would allow you to get under there and adjust when needed.

That's what I'd prefer. Doubling joists would be difficult as there's wiring and plumbing in place going through many of the joists I'll be above.

 

[fatrip]

Here is a cool site that I skimmed, I think you can get some info from it. http://badmanstropicalfish.com/articles/article28.html

 

[Gravesj1s]

I think the others are right in that you are likely to get some movement without going below the frost line.Though It would be minimal ,imo.

Another option might be steel plates,this is an alternative to digging footings when placing directly on a slab.I talked to a local archeitect about this before and have used this method per his rec.with house jacks.2' squared under each post 1/2" thick.Between the vapor barrier underneath I think if you paint the rest with a rust proof enamel you be alright in an unheated crawl space.

Im a cheap a$$ so I got them from the scrap yard at rothsteel.Just throwing and option at ya',good luck with what ever you decide.

 

[IronMan72]

Don't worry about. Get the biggest, baddest tank you can and place it dead center in the largest room in the house. Then build a shelf directly beneath it that hangs from the floor joists to put the biggest sump you can find. Lastly, make sure you place a huge sectional couch on all four sides of the tank and invite 10 or 20 of your heaviest friends by to check out your tank.

If it doesn't crash then you're all set. :strange:

Thanks for the link fatrip, it was a good read.

 

[rjmayes34]

how about them cement bases they sell at lowes or home depot for decks. just a thought

 

[magdelan]

I think that any base that will increase the surface area will work. However, I'd be afraid of that the acute pressure at the base of the floor jack might crack any paver type material.

Would a weight lifting plate work (the kind used on a bar-bell)? The 100 pound ones can be up to 18" plates.

 

[AaronReef]

Hey Cully,

I guess I'll chime in, since this is what I do for a living .

Someone else suggested the Deck Blocks from Lowes (HD has their version as well), I concur. We regularly support massive weight on these with good distribution and no cracking). I would use a 9.25" microlam (LVL) beam (available by the foot at your local lumberyard, or if you are ever in Rochester I have a bunch) perpendicular to the joists, with two short steel jack posts, sitting on the Deck Blocks.

First, you need to make sure the base is compacted as much as possible and isn't going to sink. as long as the house is more than about 10 yrs old, the base should be well settled. and you can place the blocks right on the stone, as long as it's not the round edged "pea" gravel, in which case I'd dig that out until you get to earth.

If the base is questionable, or if the crawl space is truly unheated and vented to the outside, I would recommend digging out the stone in the (I'm guessing two) areas you are going to place the supports until you get to earth (probably about 4") and then go a little deeper, in about 18" x 18" squares.

Then (this is key), take some 24" x 24" squares of a good quality landscaping fabric and put them at the bottom of the holes. This will stop the compacted gravel from sinking into the earth by making it act as one unit. Compact clean stone or crusher run (again, don't use the smooth round edged "pea" gravel), a couple inches at a time with a chunk of 4x4, until you have about 8" of base, or are at the level of the rest of the gravel in the crawl space.

Place the Deck blocks, jacks, and beam, crank-er up! After the weight is on it, check the jacks a few times, cranking up as necessary. The plastic could be cut out then the barrier re-created by installing new plastic around the jack posts taped to the old plastic, i.e., deck blocks go under the plastic.

I hope this helps!

 

[Capt_Cully]

That's what I'm talking about! Ill snap some pix when I get home. I didn't wanna have to dig but I wanna do it right. I'm planning on using 4 poles as tanks footprint is 4x3. O was thinking of sticking with the pressure treated 6x6s across the joists.

 

[Willistein]

I think 2 poles should be more than enough and have them centered under the two 6x6's.



The two 6x6's would be 3 feet on center. Which way do the joists run?

 

[Capt_Cully]

They are perpendicular to the longer dimension of the tank.

 

[mr.maroonsalty]

Hey Cully,

I guess I'll chime in, since this is what I do for a living .

Someone else suggested the Deck Blocks from Lowes (HD has their version as well), I concur. We regularly support massive weight on these with good distribution and no cracking). I would use a 9.25" microlam (LVL) beam (available by the foot at your local lumberyard, or if you are ever in Rochester I have a bunch) perpendicular to the joists, with two short steel jack posts, sitting on the Deck Blocks.

First, you need to make sure the base is compacted as much as possible and isn't going to sink. as long as the house is more than about 10 yrs old, the base should be well settled. and you can place the blocks right on the stone, as long as it's not the round edged "pea" gravel, in which case I'd dig that out until you get to earth.

If the base is questionable, or if the crawl space is truly unheated and vented to the outside, I would recommend digging out the stone in the (I'm guessing two) areas you are going to place the supports until you get to earth (probably about 4") and then go a little deeper, in about 18" x 18" squares.

Then (this is key), take some 24" x 24" squares of a good quality landscaping fabric and put them at the bottom of the holes. This will stop the compacted gravel from sinking into the earth by making it act as one unit. Compact clean stone or crusher run (again, don't use the smooth round edged "pea" gravel), a couple inches at a time with a chunk of 4x4, until you have about 8" of base, or are at the level of the rest of the gravel in the crawl space.

Place the Deck blocks, jacks, and beam, crank-er up! After the weight is on it, check the jacks a few times, cranking up as necessary. The plastic could be cut out then the barrier re-created by installing new plastic around the jack posts taped to the old plastic, i.e., deck blocks go under the plastic.

I hope this helps!

If there is any frost in the ground than this is a bad idea, there are reasons we dig footings; I too do this kind of thing. NOW would be a good time of year to get under there and see if the ground is at all frozen where you would place your supports.

2x10 floor joists can't span very far. I would see where the tank will sit in relation to any girders supporting them. If you are next to or over one, or next to an outside wall, that's a good thing. I'm thinking one might be able to run another perpendicular girder under the tank; if you could hang it from two girders you wouldn't have to figure out how it should be supported by the foundation wall. Part of me already knows the answer to this, and I would certainly check with an engineer or architect before doing anything like that. I think you are looking at 250-300 pounds dead weight per square foot or ~#2 per inch2. You may want to draw up where the tank sits in relation to all the floor supports with there dimension and your best guess as to material and try finding a structural engineer or architect who could take a quick look and give any recommendations for cheap.

 

[mr.maroonsalty]

If you can, look to see what kind of footing is used under the lally posts you already have under there; digging down will tell you exactly how any new ones will have to be set.

 

[Capt_Cully]

Pic of room where tank is going. Tank will be where TV is now. Please excuse toys and early 80's panelling and decor. We just moved in.

Fireplace is an actual hearth to outside. No basement under it. Just foundation. Wall just beyond that is in front of a laundry room which is over the crawl space.

Crawl space itself..

This is the crush on the floor of it. Droid is only thing I had for scale. Don't know how deep yet or if there is frost present.

If you take that pallet and slide flip it away from you, that is about where the tank will sit. The corner you see on the left is where the fireplace above ends and the wall that will be in back of the tank sits. The space goes back where it is below the laundry room.

moving to the right

Now on the left, you can see the foundation wall. On the other side of that is the full height basement with concrete floor. The walls of the basement are all poured concrete. Joists are 2x10s.

Space beneath the laundry room and just behind where tank will sit.

Floor just beneath the tank with the tank being parallel to the joists with a 4L by 3W footprint.