Prepping for concrete, what to do?

[sprackydoo]

I'm planning on laying concrete down in a 20 X 40 foot barn. The problem is the barn housed horses for years so the ground is 1/2 dirt and half decomposed hay so the ground is very soft. Can I lay cement over it? What if I use rebar? I don't have much experience with laying cement so any other tips are appreciated

 

[DynoDave]

I'm sure someone more knowledgeable will post a reply, but if the floor is soft, that would seem to be a recipe for the concrete to crack. I would think about digging out that soft stuff, and replacing it with compacted gravel.

 

[Ken Greene]

yup it will crack
escavate out all the soft stuff and fill with gravel, compact it with a plate tamper or jumping jack tamper.
then pour away

 

[GearHead_1]

yup it will crack
escavate out all the soft stuff and fill with gravel, compact it with a plate tamper or jumping jack tamper.
then pour away

This is the correct answer.

 

[bmwpower]

Technically, you want to compact the new dirt, then put the gravel in (1-2 inches at a time) and compact that. I would put in at least 3-4 inches of stone. Plate compactor seems to work better for this type of work.

Rebar and fiber mesh will help to prevent cracking to some extent, but a solid foundation is the best preventative measure.

If you plan on coating the floor with epoxy, paint, tile, etc throw down a vapor retarder prior to pouring the floor.

 

[sprackydoo]

Sorry I'm a newb

Don't know anything about a plate tamper or jumping jack tamper. Can I get them in 110V if not do they have gas or pneumatic ones? I'm assuming Home Depot. will rent me out one? Any special type/sive of gravel? Also what is a vapor retarder? How far apart should I lay the rebar? Should I go 4 or 6inches of cement?

 

[GearHead_1]

Sorry I'm a newb

Don't know anything about a plate tamper or jumping jack tamper. Can I get them in 110V if not do they have gas or pneumatic ones? I'm assuming Home Depot.

These are usually gasoline engines. There are general guidelines for cement thickness, bag mix, diameter and frequency of rebar. These probably vary depending upon location and local code. A good rule of thumb at least within reason is that the thicker the concrete and the more steel you put in it the more stable the slab. A good flat worker can tell you what would be best in your situation. Wire mesh (chicken wire/fencing material) doesn't work as well as rebar regardless of what some may tell you. A good compacted gravel underlayment (sometimes up to 12" thick) will help your slab also. Pea gravel is usually considered 1/2" or less in diameter I believe (someone may correct me on this). Depending upon your location and the humidity a vapor barrier may or may not be a good idea. I recently put down a 10" slab with 1' squares (3/8" diameter) of rebar for a new garage that is to have a lift in it. The lift only required 6" concrete but I decided to go above and beyond. Home Depot or Ace Rents has the plate style tampers.

There is only one sure thing, sooner or later all cement cracks (rebar will stop it from separating). Make sure your strikes or cuts are at the appropriate spacing to minimize these. If you are going to use a creeper on the cement cuts are easier to roll over than strikes.

 

[bdaz442]

concrete

A 20' x 40' foot slab is a big jog even for professional concrete people. I would NOT try this job till I did a lot of research on pouring and finishing concrete.
I've done it and it takes a lot of hard work and even more knowledge.

 

[sprackydoo]

A 20' x 40' foot slab is a big jog even for professional concrete people. I would NOT try this job till I did a lot of research on pouring and finishing concrete.
I've done it and it takes a lot of hard work and even more knowledge.

I'm gonna be doing it in 10 foot sections by framing it up with 2X6's

 

[1953mercury]

Remove loose material and bring to height with washed or screened rock as it is non-compactable and just requires leveling. Small diameter stone (3/4 minus or pea gravel) is much easier to work with than the larger stuff. Best to have someone who is familiar with the process to help. Also use a 6mil vapor barrier under your concrete. Mike

 

[rburke65]

Yes....all that soft dirt will have to come out. The area should be dug done to undisturbed soil. Your finished floor....as most projects....will be dependent on your preparation. You might want to check into a gravel/stone base refered to as #304 or a recycled crushed concrete for your base. Both get very hard when compacted. It also helps to wet the base down as your compacting. After finishing the surface you want to seal the surface and saw the concrete into 10'x10....12'x12 sections. This will give the concrete a "weakened" area and hopefully the concrete will crack in these saw kerfs and not be random on your floor. Read a lot before tackling this job. Good luck!

 

[creativecars]

I'm gonna be doing it in 10 foot sections by framing it up with 2X6's

If your really going to do it 10' sections make sure the gravel work, vapor barrier and rebar is all in place before the first section is poured. This will keep everything tied together as much as it can be. Also arond here they charge for each delivery. It may save you $ to do in bigger sections, or all at once, even if you have to hire help.

 

[pauls340]

What town are you building in?

 

[skulldrinker]

he started this 7-1/2 years ago. Is it done? If not use 3/4" limestone for the base. min 6" thick with 6 bag/4000#sq.in. That size of a slab doing it your self it will be easiest to use wire mesh with rebar in certain locations. Drill and use rebar to interlock all the slab sections. If you're experienced you can pour with the rebar in place in holes the forms.... that's how the pros do it. 8 in thick if you're parking 50 ton john deere in there. Remember the 2X6 forms go on top of the stone. In otherwords dig down 10 inches. 2-4 for gravel and 6 for crete. If this is indoor/heated you won't need expansion strip inbetween eash slab. If its exposed to weather get the crete mix with "air". Don't even get me started on all the tools you will need. Bullfloats, edgers, broom, hand troll, Finishing troll, attachment to make the lines. Don't forget to make lines. Or cut them with a saw when you're done. Always order extra. Better to send the truck back with a half yard than to be 3 wheelies short. 1 truck load = 8 yards = 4 to 5 people to finish slab. 2 wheeling 2 screeding and 1 finishing. Use construction type wheel barrows. Better to pay a laborers for help unloading instead of paying overtime for keeping the truck to long. Here in Chicago it's 6 minutes free per yard after that it's $2 a minute. 8x6=48min. and boy does that ever go fast. Have water available onsite. Maybe pour a little walkway over at your neighbors house for practice.

Trust me I've been driving a Mixer over 20 years. Concrete work is not for the timid.

 

[LW CONCRETE]

Now there is a guy who knows his concrete, dead on

 

[Prepman]

The best advice is from Skulldrinker above. You will need approx. 3 loads @ 8 yds. That is figuring a 6" slab (exactly 22.2222 yds), but get a little extra on the last truck. Pour all at once, it will save money in rental for all the equipment you will need and be a much better slab with all the wire and rebar all in place. Go to a habitat used building material place for the 2x6 form board. Run an add for an unemployed finisher and 4 helpers. I'm sure their are some around. Tell the helpers that they will need rubber boots. If it is wall to wall then you will need extensions for the bullfloat. Ask the finisher that you hire about the tools you will need, he may have some to let you use for a little extra money. Go on line and find out about the placement of rebar and wire for your area. Don't call the concrete people on the last day either.

Youtube probably have some videos on finishing to educate you a little bit. Good luck!

 

[camarotoolman]

If you have not done alot of concrete work, don't do this yourself. This is not a diy project. A contractor also gets much better prices on materials than you,so there labor is not going to add agreat deal to the cost.Also check out contractors previous work, references etc. Lots of fly by niters in this field. This is about the hardess kind of work there is.

 

[skulldrinker]

If you have not done alot of concrete work, don't do this yourself. This is not a diy project. A contractor also gets much better prices on materials than you,so there labor is not going to add agreat deal to the cost.Also check out contractors previous work, references etc. Lots of fly by niters in this field. This is about the hardess kind of work there is.

100% true. If you've been sitting in a cubicle for ten years and watching TV when you come home you will have a heart attack! Just like when you hear about those old folks dropping dead when they shovel snow. Concrete is 10 times heavier than snow.