Concrete Floors - Chime in (1 Viewer)

[snowcruiser]

So I'm hoping to finally put a concrete floor in my barn and want to hear all about concrete floors.

This is a bank barn that is over 100 years old, started as a dairy barn and was converted to horse stable probably 60 years ago. Right now the floor is just dirt with some thick oak boards in an aisle way laid over 4x4 cross members. 8 stalls are all dirt. I replaced a number of rotten posts a few years back, digging 3 foot footers filled with no shrink concrete, before replacing with 6x6 inch treated posts. These posts sit on the footers a few inches below the dirt grade. The floor will need to be poured right up to these posts. I want to remove all stall partitions and have the whole space concreted with a relatively smooth finish, then reinstall some of the stall partitions that attach to the posts.

The space is approximately 60 x 40 feet and has 6 barn doors that open outside. I may replace these doors after the pour with some bigger doors to accommodate a vehicle or two.

Anyways, what do I need to consider in hiring someone for this project?

I want a vapor barrier and am thinking about a 4 inch slab with reinforcement of some kind. Not sure if it needs expansion joints or not. I want a floor that is smooth and easy to clean, doesn't crack and will hold up to time.

What should I expect to pay? What should I look out for? What are the variables in cost?

 

[roscoFJ73]

Im not keen on pouring right up to wooden posts.I would either wrap some of foam or other material around the timber. This is so the timber can dry out if it gets damp.
My preferred way would be to cut the posts and add steel stirrups and bolt them to the floor.

Not sure what you do in the US for vapour barriers but we use thick black polythene sheeting.
The correct placement of the reinforcement is crucial. If it is in the wrong zone inside the concrete it will not have any strength. If its is not covered by concrete adequately,it will be exposed to moisture,then rust ,expand and crack the concrete.

Do you have a termite problem in your area?

The other thing that needs to be done carefully is the compaction of the soil and be equally compacted all over.If its not some parts will sink under the weight and it will crack over time. If the soil in the barn is mud based,I would remove it and replace it with clean sand.

For expansion joints I would split the slab into 4 sections.

As for the smooth surface,too smooth and you will go ass up when its wet.

I would hire someone who can talk about reinforcing,vapour barriers,compaction and any relevant local standards.
Beware the contractor who doesnt want to talk about your concerns.

Concrete can be bought in various grades from garden path type concrete up to high strength concrete for bridge spans etc
it.

 

[vasellers]

Would you be wanting any type of floor drains? Would be a good time to be deciding where to put them, where they run and where they drain outside. Make sure the concrete guy slopes the floor to the drain and doesn't just put a hole in the floor with a drain cover over it, which is a useless set up. Sloped floor with drain makes it easier to hose out.

 

[Rockets2000]

This is a great time to install a lift. It's much harder once the concrete is set.

 

[ATLcrusher]

Obviously, you'll want to use wire mesh to reinforce. You can probably use the light grade if the most this will see is a car or light truck.

x2 on a barrier between wood and concrete. Wood touching concrete = no.

My garage has smooth floors, but I'm going to put a surface finish on it. As Rosco said, smooth + wet = busted ass.

 

[batcon]

Wire mesh is pretty much useless, spend the money and use rebar and make a grid. I would check for compaction on the ground you want to pour over.

 

[Rookie2]

Are you going to be putting down a compacted gravel base below the slab? If so you really don't need a vapor barrier for this application. Vapor barriers are normally only needed/recommended in interior type areas that will have floor coverings that might be sensitive to water vapor permeating up through the slab. Otherwise vapor barriers generally have a negative impact on the way the concrete cures because they force all the water to have to hydrate out through the top of the slab which causes unequal curing and can result in slab curling.

Ditto on saw cutting control joints. This slab is going to crack, you want to control the location of those cracks. I would cut the 40 foot section in 4 equal sections and the 60 foot in 5 equal section. Fill the joints with a caulk/sealant if you want to keep them clear of dirt and debris, horse poop or whatever.

Ideally you would put diamond shaped isolation joints around your columns and aline your slab control joints with the four orthogonal points of the diamonds. Don't know how well your column layout would match up with the control joint spacing mentioned above.

 

[KLF]

Couple of things I can recommend:

* Do NOT allow the mix plant to put Calcium Chloride in the batch. They probably won't anyway, it's usually used in the winter as an accelerant. The problem is the CaCl doesn't truly bond with the cement in any chemical way, it stays as crystals in the concrete. So, later when it gets wet, it re-dissolves and leaches out of the concrete. When the puddle eventually dries, you'll have "hairy" concrete, this is the salt crystals re-forming. The vapor of the drying puddle is corrosive, just as any salt.

* An old concrete contractor told me once, there are 2 types of slabs: those that are cracked, and those that will eventually crack. Unless you plan to pour it REALLY thick (8" or so) with lots of rebar, plan for cracks. Expansion joints and partial saw cuts let you decide where to allow the cracks.

 

[ATLcrusher]

Wire mesh is pretty much useless, spend the money and use rebar and make a grid. I would check for compaction on the ground you want to pour over.

My garage slab says otherwise.

 

[Rookie2]

My garage slab says otherwise.

How so?

 

[haystax]

You should really worry more about compaction of the current base and the addition of a sand and gravel layer than the necessity of a vapor barrier for a barn floor. I would suggest the addition of fiber and air entraining to the mix and adding a couple rebar "rings" to the perimeter of the slab. Also may be worth adding a frost barrier if you are in a cold climate. The additional moisture from the roofline could lead to frost heaving under the slab in a worst case scenario. Wrap posts with a high quality roofing membrane and use the "diamond" advice from previous post. I would broom finish, especially if you are going to have animals in the building.

Labor on this type of project will not be cheap, especially if you can't access with the truck and have to place mud with a wheelbarrow or pumper hose. Flatwork is a bitch and has to be done right, this might be well beyond the DIY scope unless you have a ton of friends around to help.

 

[tag3]

Think about radiant heat in the floor, you don't have to hook everything up right away. But when you want it it is there.

 

[ATLcrusher]

How so?

I have a roughly 22x36 slab poured with the wire mesh - it doesn't even have joints cut into it. It has one hairline crack running about across about a third of the floor. I'd say it works. Poured in 2006.

 

[Rigger]

Wire mesh is pretty much useless, spend the money and use rebar and make a grid. I would check for compaction on the ground you want to pour over.

Agreed on both.

In order for reinforcing to help keep cracks tight, it needs to be positioned near the upper surface of the slab. It is easier to obtain this positioning with a grid of re-bar, chaired into place. Welded wire fabric is more difficult to keep properly positioned. Also, you can space your bars at 18 to 24 inches, and step between the bars while you work. Wire fabric gets stepped on and trampled to the bottom of the slab where it is of no help.

Ground compaction is important. Straight, flat, compacted base gravel will enhance the slab's ability to withstand concentrated loads. Spend some time here. Get it right.

 

[Rigger]

I have a roughly 22x36 slab poured with the wire mesh - it doesn't even have joints cut into it. It has one hairline crack running about across about a third of the floor. I'd say it works. Poured in 2006.

Can hardly argue with results like that!

 

[ATLcrusher]

Maybe I got lucky. I dunno. We did make sure that they actually pulled the mesh up immediately after they poured so that it wasn't pushed to the bottom. I also had "piers" poured for the lift I will eventually put in - 2'x2' each, 6" deeper than the slab - they have rebar in them.

Dirt was compacted by driving a Bobcat over it repeatedly. About a 2" gravel base.

 

[Rookie2]

Maybe I got lucky. I dunno. We did make sure that they actually pulled the mesh up immediately after they poured so that it wasn't pushed to the bottom. I also had "piers" poured for the lift I will eventually put in - 2'x2' each, 6" deeper than the slab - they have rebar in them.

Dirt was compacted by driving a Bobcat over it repeatedly. About a 2" gravel base.

Particularly since you didn't have any control joints in a slab pour that big, then it's good you had the welded wire fabric in there. The welded wire fabric is helping hold the shrinkage cracks together so they're not very visible. A 4" slab placed over a properly prepared subgrade and control joints at 12 feet +/- on center, doesn't need any welded wire fabric, although it doesn't really hurt anything.

 

[Delancy]

There are two guarantees with concrete. It will get hard and it will crack.

Base compaction is more important that mix or thickness, in the grand scheme of things,

Control joints allow for the inevitable, in a planned, sealable location, and are advisable on any pour short of post-tension, regardless of size. Minimizes spider webbing, but doesn't eliminate the possibility.

Post tension is the only means to guarantee that no separation occurs.

Formed, poured, and finished 4" floor with #3, 3' o.c.e.w. in Tulsa, Oklahoma where concrete averages $87 a yard (3500PSI) I'd estimate $2.25 psf with an additional $750 for a pump truck, assuming grade is ready to pour on.

If this is a shop, then why spend a fortune attempting to prevent the inevitable cracking?
It's not a house or commercial property, so minimizing the stress fractures is proactive, but it's easy to overspend for the purpose.

Edited; Don't pour with fiber mesh, unless you really like sweeping, either.

 

[bigbrowndog]

Maybe I got lucky. I dunno. We did make sure that they actually pulled the mesh up immediately after they poured so that it wasn't pushed to the bottom. I also had "piers" poured for the lift I will eventually put in - 2'x2' each, 6" deeper than the slab - they have rebar in them.

Dirt was compacted by driving a Bobcat over it repeatedly. About a 2" gravel base.

I don't think that was luck, just that you used the correct grade mesh needed and placed the concrete correctly. If the mesh is chaired/ tied correctly there is no need for lifting etc.
For the concrete to cure properly and achieve it's correct design strength it does need a membrane to avoid the loss of water to the sub base. This affects the cement to water ratio that is very important and also effects the finish you can apply to the surface. It is important that the concrete should be vibrated to achieve maximum results. Isolation and control joints used have been covered
[you can search these for better understanding]. Using construction joints you could break this down to four or six small pours. Don't forget the for your mates.

 

[Rookie2]

For the concrete to cure properly and achieve it's correct design strength it does need a membrane to avoid the loss of water to the sub base.

If you're talking about a vapor barrier below the slab, that's not true. A vapor barrier below the slab actually inhibits ideal curing because it prevents water from hydrating out the bottom of the slab. Since it can't hydrate out of the bottom it forces the water to hydrate up through the top of slab which results in uneven curing from top to bottom and curling as I mention previously. ACI and any other authority on concrete recommends against using a vapor barrier where you are not applying vapor sensitive floor coverings or slabs in humidity-controlled areas. IMO, a slab in a barn is the poster child case of where not to use a vapor barrier.