Concrete footing for garden raised bed question.

[esshup]

I want to make 3 raised beds for the garden, maybe more. Use 8”x16” blocks instead of wood. Make them 2, maybe 3 courses high. I will make them 20’ long x 66”-70” wide (Outside dimensions so I can drive my 48” wide tiller into and out of the garden bed). I think each bed will need around 208 blocks.

I was told to make a cement footer, 9” square and put one single #4 rebar down the center. I could use #3’s instead, bend up 5”-6” squares, run #3’s horizontally, tie them in the corners and also tie some #3’s vertically so they’d lock the bottom course to the top of the footing (I’d fill the bottom course with cement once the block is laid). The ground slopes 6” on the long side, so I’d dig down further into the dirt on one end to make the top of the blocks horizontal, and I’d use the ground as a form vs. wood forms. Put 1”-1.5” tall hi-chairs under the rebar to keep it in the center of the footing. Or should I go to the expense of buying wood and stakes to make forms?

I want to have the top course or two filled with dirt so I can plant marigolds in there to help keep some bugs away.

This area is about 50’-60’ from the driveway, so I’d have to wheelbarrow the cement to the footings. The mixer truck couldn’t drive to them without laying down mats so the grass doesn’t get boogered up. OR I could use the bucket on the FEL to move the mud - it’s about the same size as a wheelbarrow.

Is this something that I’d be better off calling a truck to deliver the mud or is this something that I would be better off mixing in my Harbor Freight electric mixer? There is an Ozinga batch plant about 7 miles away.

I want these to last 20+ years.

If I order mud, what should I tell them that I want mix wiae? Is this way overkill? (I want to minimize cracking and moving - our frost line is 36” or so down.) What am I forgetting about?

Thanks.
Scott

[span870]

Concrete, not cement.

Anyway. What I gather is you are making a garden and surrounding it with blocks. Blocks will be three rows tall. Am I correct. If not disregard everything I'm about to say. Way overkill. Understand that the ground slopes and will have to be leveled. Dig your footer bed out to level and fill with compacting sand or gravel and build on that. The footer is designed for stability in construction and a level surface but is for carrying weight. You're not supporting weight in general idea of the whole thing or not enough to concern yourself. Your idea isn't bad per say, just way over kill imo.

As far as the concrete if you go that route. Unless you have a mixer at the sight, deliver that stuff to you. Do not use a wheel barrel. Either your tractor bucket or rent a buggy or put mats down. Mats can be rented. I will tell you as an ex driver, pour it wet. There is no need for much structural integrity. I've never poured a footer drier than a good 8 slump. If it isn't self leveling, add another 20 gallons. If it is self leveling, add another 10. Rebar isn't a bad idea but it very rarely even gets used in housing. Still, don't think it's needed. If you do, remember time is a necessity. Two things guaranteed is concrete. It's going to get hard and it's going to crack.

[treetop]

You may be a bit overkill on rebar I’d probably just bend a 20 footer at a 90 and drop it in
One thing that would concern me is at 20 foot long filled with dirt it’s going to put a lot of pressure on the center area of the wall and cause it to bow break out during frost / winter you maybe wise to put a few ties side to side down a foot or 16 inches so you don’t hit them with your tiller
Sounds like a good plan but a whole lot of work I know blocks are cheeper but I wonder if just pouring a wall would cost.
Rent a trencher go down 36 48 inch’s fill half with stone stake some plywood around it and pour a short wall and stack one row of blocks on top. Not sure you’d even have to go that deep but draining the water out will help it and stone is cheep
Not sure what it cost but they pump a ton of mud around here can’t get trucks between homes.
I used a buggy when I did that veranda down buy the pond I believe it was around 50 60 bucks but I also used the bucket on my tractor so it went fast

[treetop]

Just thought about this how about those premade foam cement forms

[treetop]

Mar 6, 2022 4:27:35 GMT -5 span870 said:

Concrete, not cement.

Anyway. What I gather is you are making a garden and surrounding it with blocks. Blocks will be three rows tall. Am I correct. If not disregard everything I'm about to say. Way overkill. Understand that the ground slopes and will have to be leveled. Dig your footer bed out to level and fill with compacting sand or gravel and build on that. The footer is designed for stability in construction and a level surface but is for carrying weight. You're not supporting weight in general idea of the whole thing or not enough to concern yourself. Your idea isn't bad per say, just way over kill imo.

As far as the concrete if you go that route. Unless you have a mixer at the sight, deliver that stuff to you. Do not use a wheel barrel. Either your tractor bucket or rent a buggy or put mats down. Mats can be rented. I will tell you as an ex driver, pour it wet. There is no need for much structural integrity. I've never poured a footer drier than a good 8 slump. If it isn't self leveling, add another 20 gallons. If it is self leveling, add another 10. Rebar isn't a bad idea but it very rarely even gets used in housing. Still, don't think it's needed. If you do, remember time is a necessity. Two things guaranteed is concrete. It's going to get hard and it's going to crack.

Rebar is all I use on my homes in the slab and drives if it would crack it won’t move near as bad as fence it does cost a bit more but I believe it’s worth the cost

[beermaker]

Mar 6, 2022 4:27:35 GMT -5 span870 said:

Concrete, not cement.

Anyway. What I gather is you are making a garden and surrounding it with blocks. Blocks will be three rows tall. Am I correct. If not disregard everything I'm about to say. Way overkill. Understand that the ground slopes and will have to be leveled. Dig your footer bed out to level and fill with compacting sand or gravel and build on that. The footer is designed for stability in construction and a level surface but is for carrying weight. You're not supporting weight in general idea of the whole thing or not enough to concern yourself. Your idea isn't bad per say, just way over kill imo.

As far as the concrete if you go that route. Unless you have a mixer at the sight, deliver that stuff to you. Do not use a wheel barrel. Either your tractor bucket or rent a buggy or put mats down. Mats can be rented. I will tell you as an ex driver, pour it wet. There is no need for much structural integrity. I've never poured a footer drier than a good 8 slump. If it isn't self leveling, add another 20 gallons. If it is self leveling, add another 10. Rebar isn't a bad idea but it very rarely even gets used in housing. Still, don't think it's needed. If you do, remember time is a necessity. Two things guaranteed is concrete. It's going to get hard and it's going to crack.

You forgot the third guarantee...No one will steal it.

[esshup]

span870, thanks, I fixed it.

treetop, that's my main concern, the walls blowing/bowing out due to pressure. The ties going across sound like a great idea, that could be easily done and put low enough so the rototiller misses them. The ass that did concrete work here for Mom & Dad screwed them badly. They should have sued him but they didn't. They had poured walls going to the walk out basement doors tip in from the dirt pressure outside of the walls - these walls were about 40' long, 8" thick. He poured the slab, let that cure and then poured the walls. Not a problem, but there was no footing under the walls NOR did he use any type of steel to tie the walls to the slab.... They had to have everything torn out and redone about 7 years after it was poured. When they tore out the walls and slab there was no steel, no mesh in any of it. That walk-out concrete slab is 7' wide by the doors, 12' wide at the end. The walls taper from about 3' high by the doors to about 2' high at the end.

He also poured the driveway between the house garage and the pole barn. Dad spec'd out 5" thick because the propane truck would be driving on it. the contractor didn't put any expansion joints in it and in the Spring of the year it would put enough stress on the pole barn that the service door would get put in a bind and it wouldn't open. The only way into the pole barn was by opening the garage door. I rented a saw and cut a 1/2" wide piece out and filled it with Sika Polyurethane the 40' length of the pole barn. That strip that I cut out told a tale. There was no steel in the concrete - no mesh, AND he didn't compact and level the dirt under the slab. There were areas that were only maybe 2 1/2" thick, other areas were close to 4", not 5". I''m guessing he used 2"x4" for the form on the outside. If you turned the piece that I cut out upside down and looked at it, it looked like a picture of a mountain range. It has been cracking now for a while, some areas will lift/sink by the cracks and I might tear it out & replace it in the future. He moved out of the area about 2 years after he did the work for them and nobody knows where he went.

The area between the pole barn and the garage is 46'x55' but there was an existing slab by the garage going to the house that was 20'x28' that was left in place and the rest of the concrete was poured around it.

They had another contractor pour the driveway, he used metal forms and made it 5" thick with mesh. That driveway is 16' wide and 225' long and has no cracks in it.

Guys, if I make 3 garden beds, does that sound like it's just shy of 3 yards of cement that I'd have to order?

[steiny]

This type of thing typically does not hold up very well. The freeze thaw in soils will likely crack the blocks or the mortar joints regardless of what kind of footing you put it on, or what rebar you use.
I'd suggest using timbers rather than block, or something that will be a little more forgiving of the freeze thaw.

[esshup]

The lumber might be more forgiving, but when you look at the price of the lumber it figures out to the same price as the block and concrete. Will the lumber last as long as the block or will it rot and need to be replaced? UC4A or higher, how long will they last? I'm not talking about the treated wood that was made before they ditched arsenic in the wood, I'm talking about the stuff that is made now.

[treetop]

I can’t tell you my concrete guys orders what he wants for yardage you can call the plant give them the specks they will tell you that’s how I’ve done it when doing my little projects.
Odd he poured the slap then the walls normally it’s footers walls then slap. I’ve only done about 15 basements but they told me not to run much passed 35 foot without some kind of a offset or turn because of just that to long of run the walls will push in.

I wonder if you couldn’t fill half of that with stone put that fabric down than dirt sure would help with drainage and frost damage

[treetop]

Mar 6, 2022 15:57:57 GMT -5 esshup said:

The lumber might be more forgiving, but when you look at the price of the lumber it figures out to the same price as the block and concrete. Will the lumber last as long as the block or will it rot and need to be replaced? UC4A or higher, how long will they last? I'm not talking about the treated wood that was made before they ditched arsenic in the wood, I'm talking about the stuff that is made now.

I would think concrete would last longer my lumber beds made 17 years but not near as big as that basically 2 x 10 screwed together at the ends put on dirt fill with dirt job done

[esshup]

Mar 6, 2022 9:53:46 GMT -5 treetop said:

Just thought about this how about those premade foam cement forms

O.K., I'm curious, what should the concrete cost to have 3 yards delivered? I'll go to the local yard this week, but I'm curious for a ballpark price.

I'll be using existing soil for the form - i.e. digging out the existing soil.

[esshup]

Mar 6, 2022 16:05:52 GMT -5 treetop said:

I can’t tell you my concrete guys orders what he wants for yardage you can call the plant give them the specks they will tell you that’s how I’ve done it when doing my little projects.
Odd he poured the slap then the walls normally it’s footers walls then slap. I’ve only done about 15 basements but they told me not to run much passed 35 foot without some kind of a offset or turn because of just that to long of run the walls will push in.

I wonder if you couldn’t fill half of that with stone put that fabric down than dirt sure would help with drainage and frost damage

I have plenty of sugar sand here that I could take over there to fill the bottom half or bottom 1/3 with.

[esshup]

I know they don't have the best prices (Lowe's), but this is what I could do today to figure out the prices.

Using concrete and block. Concrete and mat price is NOT included (have to get those priced this week), but rebar, etc. is.

Each bed $377.49 roughly 20’ long x 66”-70” wide (outside dimensions)

Using PT ground contact rated, $699.09 20'x5' (outside dimensions)That is using 4x4 for the corners, 4x6 for bolting/bracing the long runs so they don't bow out and 3/8" carriage bolts to bolt the corners and runs together).

I could sure build the beds out of PT lumber quicker and it'd be less work.

[span870]

I'm lost here and maybe that's why my previous post is even confusing me.

Are you building a block wall, 3 blocks high? We are talking 24" +/- off the ground and it just surrounds your garden? The concrete footer is just a base for the blocks to sit on?

[span870]

On the original post about the rebar.

I've dealt with numerous builders, good and bad and I have my own opinions. Here's what I'll tell you for sure and you can go from there. If you are going to use rebar the single bar down the middle will do nothing but make you feel good and help minimally. Rebar is "used" to help give structural integrity to the concrete. Take a single piece and bend it. Bends fairly easy. That is the amount of integrity you'll give to whatever you place it in. You may gain strength lengthwise but that's all. If you want to use it and get any benefit for your cost you'll need two pieces running parallel to each other and tie off cross members every foot give or take. Thats goimg to give you "strength" in all directions. The chairs, unless you're real careful in pouring are going to cause you more headache then they are worth. Out of your excess rebar you have left over, take a piece and bend a hook in the end and pull the rebar up into the middle of the concrete when it's wet.

If you're really wanting to go all out and do this absolutely one time and done and build it the best you can, on your blocks get block fill and fill them up. Stagger your blocks and mortar them together.

I still think you're way over building it and worrying about the worse possible scenario but again maybe I'm not understanding fully what you are trying to do. A good base of stone compacted, add a good layer of sand, compacted, and build on top of that.

Concrete delivered is about $120 ish per yard just for concrete. Delivery fee may be added. Depending on the amount you may have a minimal amount delivery fee. The benefit is its all mixed at the same slump and same mix ratio and goes down together and saves your back. You mix it yourself and one part hardens before the other and you're going to have cold joints which will weaken anything you do.

[beermaker]

I am a firm believer in rebar and span makes some good points. Two parallel rows tied and sitting on chairs would be my suggestion. I bought a rebar bending tool at Home Depot several years ago. It's simply a heavy handle about 36" with a plate and three pegs on the end.

Concrete delivered around here is around $150/yd for retail customers. There is usually a three yard minimum.

[esshup]

Mar 7, 2022 4:24:51 GMT -5 span870 said:

I'm lost here and maybe that's why my previous post is even confusing me.

Are you building a block wall, 3 blocks high? We are talking 24" +/- off the ground and it just surrounds your garden? The concrete footer is just a base for the blocks to sit on?

The block wall surrounds the raised bed to hold the dirt in, I want to put 3 raised beds in like that. The bed will be wide enough for me to drive my garden tractor rototiller in and out, and the bed will run north/South. The footer will be there to hold the block from moving and also to stop the block from pooching out in the center of the bed due to the dirt pushing out on it, especially when it freezes. Bend rebar in an "L", tie it to the horizontal rebar so it sticks up 10" from the top of the footing. Tie that to one of the horizontal rebars and fill the lower course plus a few inches of the 2nd course with cement to lock it in place so it doesn't move.

I have a steel bender mounted on a heavy duty work bench that can bend up to 5/8" square bars, I was going to use that to bend the rebar. See the picture. That is looking at the cut away view of the rebar in the footing. I was going to bend small squares like in the picture, run 4 pieces of rebar horizontally along the footing, bend it for the corners, etc. Tie the rebar to the inside of those squares, use 2 squares on each short end near the corners, use 3 on the long sides to keep the rebar from moving around when the concrete is placed. Tie them to the hi-ghairs so if everything moves, it moves as a unit.



The squares that I bend would be pencil rod or #3's. I didn't show the upright #3's or the tie wire ties in the picture.

Right out of college years ago I worked in a steel warehouse as a foreman, then assistant plant supervisor that had a department that fabricated rebar. We had benders that could bend pencil rod all the way up to two #11's at the same time. I worked at that company floating around between departments for 10 years. The owner floated the foremen around so we could all fill in for each other when one was on vacation. There was a coil slitting dept, a sheet shearing department, a structural steel dept. (angles/bars/ronds/channel/i-beam) and a rebar/concrete dept that had rebar/mesh/nails/forms/ties in it.

[greghopper]

If you pour the concrete real wet make sure your forms have very little gaps or the concrete will leak through in them areas.

[esshup]

Mar 7, 2022 11:15:48 GMT -5 greghopper said:

If you pour the concrete real wet make sure your forms have very little gaps or the concrete will leak through in them areas.

Greg, I was going to see if I could use the dirt as the form if I could. The whole footing would be in the ground. It would be a lot of work, but hand dig the 9"x9" trench.