Gravel stabilization?

[rerod]

Hello folks..

Ive been trying to figure out a acceptable way to use 8" of gravel base, instead of a 6" poured 3'x3' slab as a base for a mobile home pier. Yes, I understand gravel wont be half as strong or stable, but you would understand why if you stood there, and considered I need to physically drag all this material under a trailer I cant sit up under..

So Im wondering, if I decide to only use gravel, which gravel would I choose? And is there a way to stabilize these gravel bases? Ive seen plastic grid 3" tall designed to do so, or mixing up a bag of quikcrete real thin and pouring it over the gravel? I know that last one will bring some comments, but you'd be looking for a alternatives short of moving the mobile home out of the way too..

Thanks

 

[Youngandfree]

If you can get under there to dig out and pile up gravel, why can't you do the concrete?

 

[carlaisle]

I don't see how dragging 6 cubic feet of gravel is less work than dragging 4.5 cubic feet of concrete.

 

[wssix99]

Are you going to keep it on the wheels and tires for a short period of time? If so, there should be nothing wrong with that.

This guide, while not helping with tire pads, may have some useful information for you: https://www.huduser.gov/portal/Publications/PDF/foundations_guide.pdf

Cement stabilized aggregate is better than regular gravel, but these geogrid designs are purpose-built for parking heavy vehicles on land/fill: https://www.landscapediscount.com/RV-Parking-Pad-Stabilization-Ideas-s/1995.htm

I have a grass paver system like in the link above ^ and its bomb-proof.

 

[rerod]

If you can get under there to dig out and pile up gravel, why can't you do the concrete?

No, the mobile home is to low to dig.. The most I can do is drag stuff around on sleds..

I don't see how dragging 6 cubic feet of gravel is less work than dragging 4.5 cubic feet of concrete.

Good point.. Ive never worked with concrete and whats the worst that can happen?

Are you going to keep it on the wheels and tires for a short period of time? If so, there should be nothing wrong with that.

This guide, while not helping with tire pads, may have some useful information for you: https://www.huduser.gov/portal/Publications/PDF/foundations_guide.pdf

Cement stabilized aggregate is better than regular gravel, but these geogrid designs are purpose-built for parking heavy vehicles on land/fill: https://www.landscapediscount.com/RV-Parking-Pad-Stabilization-Ideas-s/1995.htm

I have a grass paver system like in the link above ^ and its bomb-proof.

I think you may have misunderstood. I need better piers for my 16x80 mobile home.. But the link with the geogrid is what I was talking about..

 

[wssix99]

Good point.. Ive never worked with concrete and whats the worst that can happen?

The great thing about concrete is that you can 'chute' it. Mix it and then take two 2X10s and screw them together in a V-shape. Pour the concrete in the trough and you can slide it downhill with a shovel vs. moving material around on the ground. ... Much easier.

You will need to consolidate concrete and get the air bubbles out. You can do this with a rod of rebar and just poke it. (I'm sure there are youtube videos on this...)

The other thing with gravel is that you will need to vibrate it in order to consolidate it and get it solid. If you are working under the home, I'm not sure how you would do this:

I think you may have misunderstood. I need better piers for my 16x80 mobile home.. But the link with the geogrid is what I was talking about..

Can you share a picture of your existing pier and what you are dealing with?

 

[rerod]

The great thing about concrete is that you can 'chute' it. Mix it and then take two 2X10s and screw them together in a V-shape. Pour the concrete in the trough and you can slide it downhill with a shovel vs. moving material around on the ground. ... Much easier.

You will need to consolidate concrete and get the air bubbles out. You can do this with a rod of rebar and just poke it. (I'm sure there are youtube videos on this...)

The other thing with gravel is that you will need to vibrate it in order to consolidate it and get it solid. If you are working under the home, I'm not sure how you would do this:
Can you share a picture of your existing pier and what you are dealing with?

Thanks for the tip about the need to consolidate the concrete..

You might be able to fit a compactor under the tallest area under the mobile home, but the low side you can not sit up under.. But that chute sounds very valuable everywhere hopefully..

My piers look similar.. But I cant even find a 16x16x4 let alone any bigger. Crazy engineers..

 

[PCustoms]

Preformed Concrete cookies/pads?

 

[BillK]

I think you are overthinking the entire project. How long has the home been sitting there ? It has been on plywood ? I assume you are going to jack up one section at a time and replace the footing ? I would do that and just pull out the old plywood, put down a few inches of CR6 or whatever they call it in your area, get the biggest patio paver you can find to put on top of it instead of the plywood and then put your blocks back. It will probably be there longer than you

 

[Hank11]

You need a couple or three stout young guys to help.

Build temporary supports on each side of the one you are replacing. Jack up slightly. Dig down about 6 or 8 inches leaving undisturbed soil at the bottom. Lay your 2x6 form over the hole, level and stake it. Pour concrete. Use the fast curing 5000 lb. stuff.

Next day build your block piers on top. Get final level with steel shims. Knock out temps and you are done. Better than most any trailer around.

 

[brewchief]

Can you replace the pier pads all at once or do you have to do it one at a time? If you coulde simply place a new pad next to whats existing it wouldn't be that hard to dig out a 3x3 area, add a form then when all are ready get a concrete pump and order a pumpable mix from the redimix supplier, pump them in and screed them off and then build new piers in a couple days.

 

[rerod]

I think you are overthinking the entire project. How long has the home been sitting there ? It has been on plywood ? I assume you are going to jack up one section at a time and replace the footing ? I would do that and just pull out the old plywood, put down a few inches of CR6 or whatever they call it in your area, get the biggest patio paver you can find to put on top of it instead of the plywood and then put your blocks back. It will probably be there longer than you

I dont trust 2" pavers.. They will crack. I need something at least 24x24x4 for me to consider it. Better yet 3x3

You need a couple or three stout young guys to help.

Build temporary supports on each side of the one you are replacing. Jack up slightly. Dig down about 6 or 8 inches leaving undisturbed soil at the bottom. Lay your 2x6 form over the hole, level and stake it. Pour concrete. Use the fast curing 5000 lb. stuff.

Next day build your block piers on top. Get final level with steel shims. Knock out temps and you are done. Better than most any trailer around.

I have my son who will help, but I have the rest of my life, so no rush.. Your plan sounds good.. What I need to do is have a redimix guy come out and look and see weather they can chute or pump concrete 4' back from the outside wall. If he can, I build all 20 some forms and stake them in-between the existing piers, so we can pour it all in one day.. My only concern is that we cant possibly finish the surfaces of 20 some 3x3 slabs, so why not drop 16x16 concrete pavers in the center of the wet concrete, level it and move on?

Can you replace the pier pads all at once or do you have to do it one at a time? If you coulde simply place a new pad next to whats existing it wouldn't be that hard to dig out a 3x3 area, add a form then when all are ready get a concrete pump and order a pumpable mix from the redimix supplier, pump them in and screed them off and then build new piers in a couple days.

Exactly..

I need redimix to inspect, and set all forms between the existing piers. What do you think about dropping a 16x16 paver in the middle to insure a fast flat surface for the first two 8x8x16 CMU blocks?

 

[Hank11]

Unless the soil in Iowa is mucky, I’d go 24x24” for the pads. 4” is probably thick enough. 3-4 bags per pad. Mix from bags and just do a few at a time so you don’t kill yourself. Get a couple of small mortar tubs. Tie a rope on one end (make a hole for the rope) and just pull it under the trailer, then tip up to dump in the form. Try to move it in 2-3 pulls so its not too heavy. You may be able to pull the rope from the far side of the trailer. A 3rd guy would sure help.

For finishing, just screed them off with a piece of 2X. No need for troweling.

 

[brewchief]

I dont trust 2" pavers.. They will crack. I need something at least 24x24x4 for me to consider it. Better yet 3x3

I have my son who will help, but I have the rest of my life, so no rush.. Your plan sounds good.. What I need to do is have a redimix guy come out and look and see weather they can chute or pump concrete 4' back from the outside wall. If he can, I build all 20 some forms and stake them in-between the existing piers, so we can pour it all in one day.. My only concern is that we cant possibly finish the surfaces of 20 some 3x3 slabs, so why not drop 16x16 concrete pavers in the center of the wet concrete, level it and move on?

Exactly..

I need redimix to inspect, and set all forms between the existing piers. What do you think about dropping a 16x16 paver in the middle to insure a fast flat surface for the first two 8x8x16 CMU blocks?

I would think putting anything in a poured pad would create a weak area, If the forms are level you should be able to screed off the top of the forms and be really close. Once all the pads are poured and the pumping is done there still should be plenty of time to go back and trowel a smooth finish.

Talk to whoever you can rent a line pump from about your plan, they will have some insight as they have probably already done something similar.

 

[rerod]

I think you are overthinking the entire project.

You mean Im so dumb, I should have been born with the knowledge to do everything without advice? That's really what what that sounds like..

I would think putting anything in a poured pad would create a weak area, If the forms are level you should be able to screed off the top of the forms and be really close. Once all the pads are poured and the pumping is done there still should be plenty of time to go back and trowel a smooth finish.

Talk to whoever you can rent a line pump from about your plan, they will have some insight as they have probably already done something similar.

I didn't mean embed the paver into the slab deep.. Just level it on top and ensure 100% contact only because it's fast and I don't know how much time it will take me to finish 20 some slabs because no one in their right mind wants to crawl down there..

I cracked a couple of blocks while I was leveling it years ago. Scary, because if one pier failed, Im not sure it wouldn't set off a chain reaction and they all fail.. They cracked because the piers were stacked off of plywood, which is now rotted away allowing the blocks to tip and move independently.
I think if I have anything other than a super flat paver surface, my blocks might crack again.

 

[rerod]

Unless the soil in Iowa is mucky, I’d go 24x24” for the pads. 4” is probably thick enough. 3-4 bags per pad. Mix from bags and just do a few at a time so you don’t kill yourself. Get a couple of small mortar tubs. Tie a rope on one end (make a hole for the rope) and just pull it under the trailer, then tip up to dump in the form. Try to move it in 2-3 pulls so its not too heavy. You may be able to pull the rope from the far side of the trailer. A 3rd guy would sure help.

For finishing, just screed them off with a piece of 2X. No need for troweling.

Thanks..

Yeah, 3'x3' footer should probably be 10" thick, not 6.. But 3'x3' might be overkill..

 

[BillK]

You mean Im so dumb, I should have been born with the knowledge to do everything without advice? That's really what what that sounds like..

I did not mean that at all. I am just thinking if it has been there for (?) years sitting on plywood and has just rotted the plywood away that something to replace the plywood would be all that you need and a 2" thick 2x2 paver would probably be way more than enough ?

I am not a structural engineer but I did a little searching and it looks like a mobile home your size weighs in the vicinity of 40,000 lbs ? Distribute that over 20 pads and its 2000 lbs per pad. I would almost bet that a 2" pad will easily support that much weight. Put it on a good compacted "gravel" base and you should be good to go.

Thats just my opinion. Trying to save you a bunch of work.

 

[brewchief]

So if it was on plywood before why not put it on plywood again? Foundation grade plywood is available, build a pad out of multiple layers nailed together. If 24x24 would be large enough one sheet would get you 8 layers thick (6 inches thick using 3/4 ply).

 

[readhead]

Is this being brought on by financing or insurance? I have actually done this several times. We would remove the skirting at each location, use a small backhoe to dig out the footing, pour the pads with the rebar sticking up and then set and grout the blocks. I left out temporary supports.
We would be back in about five days to shim the frame level and weld the long piece of rebar to the frame and put the skirting back up. It’s not as hard as it might sound. Just rinse and repeat.

 

[ycgoat]

I have seen mobile class rooms moved into place, jacked up, and set on CMU stacked on 2'x2'x1/2" steel plates, shimmed to level, and strapped down. then the wheels removed and stored underneath.

 

[NUTTSGT]

Get your CMU blocks, fill them with concrete and set them on top of 24"x 24" pavers.

I doubt the ground under the plywood is going to settle anymore after the trailer sitting on it for 20 years.

 

[rerod]

I did not mean that at all. I am just thinking if it has been there for (?) years sitting on plywood and has just rotted the plywood away that something to replace the plywood would be all that you need and a 2" thick 2x2 paver would probably be way more than enough ?

I am not a structural engineer but I did a little searching and it looks like a mobile home your size weighs in the vicinity of 40,000 lbs ? Distribute that over 20 pads and its 2000 lbs per pad. I would almost bet that a 2" pad will easily support that much weight. Put it on a good compacted "gravel" base and you should be good to go.

Thats just my opinion. Trying to save you a bunch of work.

Thanks.. 2000 lbs per pier sounds accurate when its sitting there, but when you start jacking for leveling, those pads will see twice the weight. I broke hardwood bridge planks 3" thick while I was leveling, so I know a paver wont survive if I level off of it. If I have cribbing for my jack and set the home down nicely, maybe, but you never know when one pier has more than the other, and Im not dealing with cracked pavers designed to be walked on..

So if it was on plywood before why not put it on plywood again? Foundation grade plywood is available, build a pad out of multiple layers nailed together. If 24x24 would be large enough one sheet would get you 8 layers thick (6 inches thick using 3/4 ply).

A sheet of AC2 3/4 Pressure Treated is $125, when one concrete footing's concrete, rebar and form are $25. Same goes for 1/2" steel plate=big money and short lived.

remove the skirting at each location, use a small backhoe to dig out the footing, pour the pads with the rebar sticking up and then set and grout the blocks. I left out temporary supports.We would be back in about five days to shim the frame level and weld the long piece of rebar to the frame and put the skirting back up. It’s not as hard as it might sound. Just rinse and repeat.

Im pretty sure a backhoe wont be able to reach 4' under the home.. Most of the skirting was less than 24" tall..