RV Garage Floor question

[RndmTraveler]

We just had a new garage build for our MH, and need some advice regarding the floor.

I have 2 quotes from 2 different companies:
Option 1: 4” concrete floor, 3” gravel base, fiber mesh reinforcement, saw cut joints.
Option 2: 5” concrete floor, 3-4” gravel base, rebar reinforcement, saw cut joints.

Option 2 is more than double the cost of opt. 1. Company 1 does this all the time, and claims that the fiber mesh reinforcement is more than enough. Company 2 has only done a few floors, and keeps telling me that you can never be too strong… however, the $5000+ price difference makes me think twice.

Our 35’ MH weighs 24K.

[LINADR]

What is the concrete strength to be used?

[Burgy]

we used 4000 psi mix 5 inches 24 by 24 footer under footer under the main door. Wire mesh rebar and microfiber

[RndmTraveler]

I don't know... its not specified

[FIRE UP]

Well,
I can tell you this. Our home is right at 18 months old. It came with a 16' wide by 53' long RV garaged attached. Out here on the west side of the planet, the builders pour the slabs FIRST before building on them. The RV section of the slab is 4" thick, 3000PSI, Fiber meshed concrete. Two weeks prior to our closing date on the home, I and the builder, authorized the application of two coats of industrial Sherman Williams Epoxy floor coating with two accent/guide stripes and, two coats of clear Epoxy.

Our 27,000 lb. 2004 Itasca Horizon 36GD with the C-7 330HP CAT has been sitting on that floor, on and off, (depending on traveling sequences) for the 18 month period. So far, not one micro-sign of any cracks or fatigue, anywhere. This particular builder installs 6" of compacted road base, under the RV slabs. Under that is standard DESERT dirt.

I just had another slab poured on the outside of the RV garage. It's 16' wide x 72' long and it also is fiber meshed, 4.5" thick, 3000 PSI colored/stamped concrete. That company put no road base under that slab, just graded the decomposed granite to the depth needed for the finished slab height. So far, that slab is 4 months old and, has some signs of small cracks, right where they're supposed to be, IN THE GROOVES installed while finishing the slab.
Scott

[jacwjames]

Probably the most important thing is the spacing of the cuts & size of the resulting slabs.

I would go with the fiber reinforced concrete, pretty much proven technology but you may want to ask them the amount of fiber they intend to use, may be lbs per cuyd or some other measurement. If it sounds reasonable go with it, or ask them to put more if in doubt.

[iRent2u]

Originally Posted by RndmTraveler

We just had a new garage build for our MH, and need some advice regarding the floor.

I have 2 quotes from 2 different companies:
Option 1: 4” concrete floor, 3” gravel base, fiber mesh reinforcement, saw cut joints.
Option 2: 5” concrete floor, 3-4” gravel base, rebar reinforcement, saw cut joints.

Option 2 is more than double the cost of opt. 1. Company 1 does this all the time, and claims that the fiber mesh reinforcement is more than enough. Company 2 has only done a few floors, and keeps telling me that you can never be too strong… however, the $5000+ price difference makes me think twice.

Our 35’ MH weighs 24K.

Just completed ours in June. We went with 5000 psi, road grade wire mesh and 6" thick. So far so good.

[Old Radios]

I went with 6" thick, Fiber mesh. On my 40'x30' it was $400 more than 5" thick.

[RndmTraveler]

Thanks for all the replies…
our shop/rv garage is 40’ x 45’. The middle section is for the mh (40’ x 18”, 16” high).

The architect suggested to go with opt.1 (4” fiber mesh reinforced concrete, 3” gravel base). He thinks it is sufficient.

I am inclined to follow his advice, especially after reading that others also have a 4” floor. The price difference is also considerable ($5000+).

[LINADR]

Just curious, did the architect say why a gravel base? Personally, I'd do a DG base. I think you'd get better compaction from it. I'd also do a minimum of 3000 lb compression strength concrete, 3500 I'd recommend... I'm not an architect, but I did stay at an RV Park last night..

[jfran304]

I would probably go with the thicker concrete in case I ever decided to buy a heavier coach.

Jon

[FIRE UP]

While having higher rated concrete and, other additions, i.e. steel, fiber mesh and more, the primary protection for any slab is a stout, stable base. If one has expansive soil, clay, or anything other than good DG, rock (small), road base, and a few others, it's advised to dig down quite a few inches of your expansive soil/clay etc. and replace it with gravel, road base, DG, etc. Than compact it as best as possible.

Then, even a minimal rated concrete slab will work just fine. As long as the base, below the slab is good and stable, you'll be fine.
Scott

[hayward3411]

Option #1- I have a 31,000 lb on slab over 3 years, no cracks, looks good.

[Gary RVRoamer]

I think Fire Up is on target. The base prep is critical, as is the drainage under the slab. If there is water draining through the area underneath the slab, some form of crushed stone or gravel is probably key to preventing erosion. If packed desert sand, that's not a worry. The base should be firm enough and sufficiently drained so that the slab is firmly supported and stays that way.

Next comes the wire mesh and/or rebar, which gives the concrete structural strength to withstand bending. Yes, concretes bends under stress. Fiber in the concrete helps too. Placing several thousand lb loads (the wheels) 20+ feet apart on a slab creates a lot of torque on the slab, so you really need all that structural strength as well as a firm base underneath.

The psi of the mix does not seem important to me. That refers to the compression strength of the concrete, and that's not much of concern. Figure out the lbs/sq inch of your RV tires (weight vs tire patch size) and you will see it is maybe hundred lbs, not thousands. Hint: the air pressure in your tire is the same number. 3000 psi is plenty if the rest of the construction is done right.

The cuts are expansion joints, designed to cope with temperature change. Cuts are in lieu of separate slabs butted together.

Concrete Basics in Construction from Construction Knowledge.net