Concrete pad for 31K pound Allegro

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Mar 27, 2005
I am having my driveway replaced due to damage from sinking over the years.  I want it to be strong enough to park our motorhome on.  In researching this on the net I've determined that 6 inches of concrete on a good base should hold.  Can anyone with experience in this verify my numbers?  Also, I have gotten estimates from several reputable contractors in my area (West Alabama) and none of them will give a warranty, nor will they tell me how thick the concrete should be to hold this much weight.

Any and all help will be much appreciated.

Billy Crowell
2003 Allegro Phaeton
When I laid a 40'x15' concrete pad for our old coach I used 12" of compacted base rock and 8" of concrete with rebar. I knew I was over-building it and 6" of concrete on 6" of base rock would have been adequate, although I can't produce any figures to substantiate either number.

For clarification 'base rock' is a term used by landscape materials suppliers for crushed rock.
[edit]Added base rock explanation[/edit]
You're in the right ballpark, though probably on the minimum side.  A friend of mine installed a pad a couple years ago and I think he had 8 inches poured over wire mesh and a crushed stone base. I don't recall the full details but will email him to see if he remembers.

There are several grades of concrete, sometimes referred to as "mixes" and graded by their pressure ratings.  3000 psi mix concrete is stronger than 2000 psi mix, for example.  And as Tom mentioned, the use of rebar and/or wire mesh is also a major factor in strength and resistence to pressure cracking, as is the underlying base and overall ground preparation.  If the ground is soft or wet, you may need some deep footings poured as well.  As in many things, the prep work is all-important to a quality, lasting job. 

And if the contractor cannot talk intelligently to you about about loads and the construction techniques for handling them, you don't want to do business with him.  Your needs are more like highway construction than a residential driveway, so you need a qualified contractor.

You might contact a local concrete manufacturer and ask what they recommend for your application - and maybe the name of someone who can do a quality job of it.  But I doubt if you will get a guarantee from anybody, at least not beyond 30-60 days. Too many variables and too many uncontrollable factors.
RV Roamer said:
There are several grades of concrete, sometimes referred to as "mixes" and graded by their pressure ratings.

Thanks for the reminder Gary, I'd forgotten all about that. I found concrete suppliers very willing to discuss the "right mix".
Another thing I did was to ask for 6-1/2 bag mix.  This means there are 6-1/2 bags of cement in each yard of the concrete.  This really strengthens the pad.

In June of this year I just had a 12 x 30  concrete pad poured to park my 34ft bounder on. The contractor poured  3000psi fiberglass reinforced  6" thick. Because it was poured on a sloped area and i wanted the pad level, he back part of the pad is 3 ft thick. So far so good
Hi Billy,

I would say 6" would be minimum. We have a concrete pad in FL that I believe is around 6" but have never dug down to see. I do have cracks in it because they apparently didn't use any rebar. Be sure to do that no matter how thick you make the pad.

You guys are right on about the sub base wet/dry that makes all the dif .Also 6&half bag is good.My base here is so good that I don`t use conc. We have sand that compact`s so hard it is great.I park the MH in the pole barn on sand & from the street to the barn I just drive on the grass. You can Hadley tell where I drive.This has been going on for years. Keep up the good work. Don

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