Do I really need anything more than a 4" concrete slab to support a bus?
One of the cities I'm looking at for a lot to build a house requires a asphalt/concrete driveway and I don't want asphalt again.
Brian Elfert
Not if you like to look at big cracks!! I mean in the concrete. The front of a bus may be OK but a MCI has 10 tons on the rear. I wouldn't think of less than 6" with reinforcement. You could probaly hear 4" breaking under you.
In my Garage I poured 4" on the car side and 6" on the bus side. Jerry
Shop floor 50'x28' with 40' pit...... conc. 4" to 5" thick, 3/8" rebar at 18"centers both ways, hard concrete with fibers on a good solid base.....
Two MCI-9's parked on it and no cracks in 3 years....
Iver.
Iver has it right - What's your sub-base (soil condition)? With the proper sub-base and 3000 psi fibered concrete 4" MIGHT BE DOABLE - FWIW
I have a 300 foot concrete driveway, a 100 X 50 concrete pad between the house and the garage, and the 30 X 50 garage where the bus is parked. All of this is a 4" slab that is 10 years old with no problems. I also have hydraulic jacks on my bus and have had all wheels off the ground for extended periods placing all weight on the the jacks. The base is important. Of course I do have an Eagle and some of you would say that since half of it has rusted away, it doesn't weigh much!! ;D
Tom Hamrick
1984 Eagle 10S
Along with the question of good base, I notice Iver says 4" to 5" of concrete. Most contractors use a 2 x 4 (3 1/2") for a form and then tend to push a little extra dirt toward the center. The 4" slab you pay for may be less than 3" where you put the wheels.
On the property/house we just purchased there is a 310 foot long driveway (concrete) and a pad off the house that measures 75x50. This is where we are building a shop combined with 2 car garage. The contractor had to cut out part of the slab for footers and he measured 6 inches thick and while cutting and digging he had to cut thru rebarb and wire mesh. It was a job to say the least. Our neighbor tells me that the previous owner had a small business that involved trucks. Don't know how large but the slab is not hurt in any way. I think it will handle the buss easy!
Now my old house had a 4 inch thick driveway about 45 foot long. Just long enough for the bus, but after making a stone pad for the bus I noticed where the driveway has cracks in it where they weren't before!
If you can afford it, do the better thing and make it right for the bus! It's a lot more expensive to fix it later!
Ace
The base is all important in determining the type of pad on top. So is the quality of the work in pouring the slab.
I poured 7" thick & paid extra for 4000psi concrete. 1 year later, I had cracks & shifting. The contractor isn't in business any more (I can't imagine why), so I'm stuck with it. >:(
I did my own driveway about 2 years ago. I didn't have the bus at the time.
I dug it out to at least 4" and in most places it was 5".
3000lb concrete.
I had cracks before the bus, but they have not gotten worse since the bus.
Most driveways I see in this area have cracks.
Around here they pour directly on the clay ground.
.
Brian,
As long as you have good preparation before you pour, and use the fiber reinforcement, you should be ok with the 4" slab. The problem with concrete cracking is when it is on poorly prepared soil and/or not reinforced properly. Concrete generally cracks when there is movement beneath it, or it's uneven somewhere.
But if it really concerns you, pour an extra foot near the rear where the bulk of the weight will be.
I'm not an expert on concrete, but I did stay at a Holiday Inn Express last night ;D
If you could place the concrete & more particularly the rebar perfectly then 4" is likely enough. Perfectly for a 4" slab means 1/2" rebar exactly 1" up from the base on probably a 1' grid. Since we live in the real world and concrete placers get the rebar "somewhere" inside the slab as opposed to perfectly located in the bottom 1/4 of the slab, I would bite the bullet and pour 6". If you are going to go with the 4" then be absolutely anal about the position of the rebar inside the slab. And as you have already been advised compact the living H out of your base.
Brian:
In addition to concrete thickness, I'd personally use 4,000 psi and certainly rebar. One key element is site preparation. Your pour/pad will only be good as the area you prepare. 3/4" modified which has been compacted with a vibatory roller would be ideal. Get the base in which you are going to pour on compacted, stable and tight. No voids, etc. Oh ... and yeah, I'd do 6" min.
Just my $0.02,
Jerry H.
:) I am in the process of building an area for my bus 12 x 75 feet beside my garage and though I am not doing concrete I dug down 12 inches with my bachhoe and put in the 1 1/4 inch processed stone like they use for highways and compacted it. This was done last fall so it could sit all winter and get further compacted by the bus and also by being rained on which will settle it more. Then this year the contractor will be using the highway base blend which has larger stones and is coarser and will support more weight. If you live in the west where your rain fall in near zero, I would compact like they said and then soak it with water and let it sit for a few months to settle more. Don't be in a rush to get it done. My orginal driveway has lasted 20 years before I saw some cracks showing up, I initially put in a 12 inch base when I built the house. Most contractors will say a few inches is good but when it cracks later they have your money and you have the problems.
Good Luck.
Good info. I may need to look for a lot in a city that doesn't require a paved driveway. The budget for my house project is already stretched to the limit. I don't think I could afford a 6" concrete driveway and I really don't want asphalt with a bus. My project includes a 1100 square foot home with basement plus a 2600 square foot building for the bus and a shop.
I assume I will need a 6" slab in my bus garage/shop too then. The current plans for the garage/shop only specify a 4" slab.
Brian
Along with the base prep and rebar - if you know where the bus will be parked, could you not just pour 6" - 7" footings beneath that spot, and leave the rest of the floor at 4". I don't think i would put 6" in an entire building of that size. Up here with the cold winters, it seems that they all will crack eventually, so just design it with the relief joints so the cracks will show up where you want them.
Just our way. We poured a 28' X 58' slab for our shop. We knew where the bus would be parked, so we poured that part 6" thick with 6" wire mesh and 5/8" rebar. The rest of the floor was poured 4". We also poured the 4' X 14' approach to the bus door 8" thick. All concrete had the fiberglass mesh added when mixed and we used 3000# mix. We have had no problems so far. Of course living in SW Florida, we do not have freezing and thawing to deal with. Our driveway is 2" asphalt. We have no had no problem driving the bus over the driveway, but I would not consider parking the bus on the asphalt for extended periods of time. Jack
Brian: Before you discard the idea of thicker concrete, calculate the additional cost of the concrete as a percentage of the total cost of the building. If you are going to have an insulated heated shop, an extra 2" of concrete will be a small percentage of the overall cost. On the driveway, the pecentage increase will depend on the amount of money spent on the base, rebar, forming, placing and finishing. These costs are fixed and the additional cost is only the cost of the concrete.
If you plan on installing a car lift in your shop, 6" concrete makes the install a simple bolt in.
Seems like things never go according to plan anyway. Is it possible to install the garage concrete later & just use gravel until then? While not ideal, this worked out OK for me in the past.
If the neighboorhood requires a paved driveway, there will be more restrictions forthcoming. Me thinks you will be ahead if you can find a suitable spot with fewer requirements.
Building ain't getting any cheaper. :(
Quote from: kyle4501 on March 08, 2007, 10:21:18 AM
Seems like things never go according to plan anyway. Is it possible to install the garage concrete later & just use gravel until then? While not ideal, this worked out OK for me in the past.
If the neighboorhood requires a paved driveway, there will be more restrictions forthcoming. Me thinks you will be ahead if you can find a suitable spot with fewer requirements.
The type of building I am having put up requires a floating slab or other type of footing.
The restrictions are by the city, not the neighborhood. There is no HOA or any covanents. I've decided I probably won't build in that city because meeting the requirements increases the cost too high.
It is next to impossible to find a lot around here that will allow a large outbuilding and not be 60 miles out. The cities even 30 to 40 miles out all have pretty restrictive rules on building.
Brian Elfert
Brian I have never heard of a "floating slab"! Can you please explain?
Thanks
Ace
Quote from: Ace on March 08, 2007, 11:27:37 AM
Brian I have never heard of a "floating slab"! Can you please explain?
Thanks
Ace
Here are a couple of explanations I found via googling.
Quote"floating slab" -- it "floats" on the soil, with the deeper concrete around the edge holding it in place. In northern climates, the concrete around the edge has to extend deep enough to remain below the frost line in winter.
QuoteFloating Slab
A floating slab is a reinforced slab placed between walls or footing. The footing poured for a floating slab is allowed to set and the forms are removed. The slab floor is poured inside the footing and is separated from it by an expansion joint. This process of pouring the slab separately allows the slab to rise or fall without causing cracks at the footing edges.
A floating slab is simply a slab of concrete that rests on the earth with no frost footings. It floats above the frost during the winter months. The edges are thickened to support the weight of the walls. The edges are also insulated in an attempt to keep the ground underneath from freezing.
Brian Ellfert
My shop is 40'x60'. The slab is 7" thick with a 12" wide x 24" deep perimeter beam. There are also 2 lateral beams (40' length) on 20' centers and 1 longitudinal beam (60' length) right down the center....all are 12" wide x 24" deep. All on top of a nice pad of select-fill soil. I have not had any slab problems while parking my '85 Eagle, tractor and 1,000's of pounds of other junk. :)
Darrin