RV Concrete Pad Questions

I poured a 16'X40' slab for my Rv 3 years ago. I started with 4 inches of stone compacted with a heavy diesel compactor. Then we poured 8" of 4000 psi concrete. So far not even a crack in it.

Our foundation on our new RV/truck barn was overkill I admit and was mostly due to my specs but did not want any slab problems. It is a monolithic slab (no joints), 6 inch thick with additional 18 in thick by 24 inch wide beams around perimeter plus two similar sized beams down each side of central bay where RV will be parked. Six #7 bars in each beam tied into #5 rebar grid 16" OC. Also has brick ledge around perimeter to add stone wainscot to match house in the future.

Also added a threaded floor drain which is located just below where the RV utility basement compartment will be. Concrete contractor sloped concrete 3 feet around and down into drain with a 1/4 inch per foot pitch. Has the recessed (slotted style) cap.

Getting the slab coated with commercially contractor applied epoxy next week.

Will add 6 inch driveways with somewhat smaller perimeter beams next year.

Without knowing your soil type, any filled areas, and compaction... we are guessing. Based on the 12x12 footer I would go with 3000 and fiber and 4" thick except where the tires will run and then 8"x 24" X 50' . I would run a single #5 rebar long ways under where the tires will run with 3' #4 rebar cross ways every 2-3'. You need to saw it down the middle and every 12.5' cross ways to control where it's going to crack.

They just poured my MH garage pad 6" and 12" around the edges. 25 by 50 ft. Fiber in concrete and re-bar. A little under $7k. Included grading and forming.

A lot depends on the soils in your area and the subgrade you use. 2500 psi concrete is more appropriate for sidewalks. I would use 3000 psi concrete. In some areas with expansive clay soils, rebar and wire mesh may not be enough and post-tensioning works better.

When I built my RV garage, they used a 4" slab with #3 rebar at 24" each way, which is pretty minimal. It's fine for this area even with a heavy coach like mine. It might not be right for your area, so it's worth getting with a contractor who has some experience in this type of work.

I've been in the rebar business since 1980, doing everything from small residential projects to huge projects with thousands of tons of steel. I should clarify that 6 x 6 mesh doesn't mean anything. That's the wire spacing. There is also the wire size or gauge. For example, 6x6-W2.9/W2.9 is a six inch spacing each way with 6 ga wire each way...a common size.

PastorCharlie wrote:
When I poured my shop floor I poured 6" with three courses of 5/8 rebar around the edges and 4" with wire and 5/8 rebar crisscrossed in the floor.

I agree, I poured an extension to our utility driveway and is 6". The rest of the driveway is 4" and just driving the MH on it cracked it in several places but no cracks in the 6" slab.

Probably as important as the concrete slab on grade is the compacted base below. I would use 6" thick compacted granular fill, with 6" thick reinforced concrete slab over.

A quick calculation for weight per tire would be: ~9"x9" footprint, which increases to 21"x21" with a 6" thick slab = 3.06 SF "footing" per wheel. Assuming 2,500 PSF soil bearing pressure, that would support ~7,656 LBS., which is just about what you are hoping for.

Edit: Oops, math correction

The footers are great and they do give additional support.....for the building. The footer is only on the perimeter and does nothing to support the weight of your coach. I would go with a 6" slab, reinforced with 6x6 mesh and using 3000 pound fibermesh concrete.
By the time they cut expansion cuts in the slab, you will need the additional thickness to prevent settling of the slab.
I would also specify that the slab is poured LEVEL, rather than having a slope towards the door. Even here in Florida, where we get a lot of rain, the level slab is much easier/safer when dealing with vehicles that will be worked on and on jack stands. Before the garage is built, a level slab will allow any water to run off just fine.

If you intend to park it for a long time put something under the tires between them and the concrete pad. Both Michelin and Goodyear say this needs to be done. Maybe there is something on their web sites. I remember a engineer from Michelin saying a piece of plywood is OK. Please check it out.

I'd go 6" and get a higher PSI concrete.