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Old 05-20-2014, 09:25 AM   #1
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Motorhome Garage - Concrete thickness

I am considering building a garage to store my Monaco Dynasty during the searing summer heat and winter cold. I have searched the archives here on iRV2 but find no recommendations on concrete thickness for the floor of the garage or the or drive. Searching other on-line forums, I see a recommendation for either 5" or 4" floor thickness, 3500# minimum concrete with 1/2 " rebar on 24" centers. My Dynasty tag is standard weight. My soil is sand near my house, or clay near another property I own.

A related issue is anything else to consider when building, beyond the possibility of dumping, 50A full electrical service, water? I will build it large enough to easily handle any future bigger motor coach that I might buy. I will also most likely build it large enough to store a farm tractor and general storage of other rarely used items.

Experience and recommendations are welcome.


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Old 05-20-2014, 09:30 AM   #2
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Here's a previous thread that has some posts discussing thickness.

Motorhome Garage


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Old 05-20-2014, 10:03 AM   #3
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Gary when I built my shop, 40' x 50' it was in hopes of someday having the coach I now have. That was as big as my property would allow and I am thankful this coach fits. It was classified as a 43' and measures more in the 45' range. I knew I would have a heavy coach so the cement guys I used said a 5" thick floor with fiberglass strands throughout is what was the hot ticket 10 years ago. I thought I would have to have rebar as well, but they said not. I do have heat & A\C in the shop as well as excellent insulation. I didn't do water as I live in the country and if I put a floor drain in it would have required another septic system. The excellent insulation and heat and A\C were after thoughts and cost a lot more to add. I didn't think I would use it for anything other than indoor storage, but it has turned into a man cave and toy barn. Do it up right the first time and it will cost less in the long run. Randy
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Old 05-20-2014, 05:27 PM   #4
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MYy 40' wide X 60' deep X 15' sidewall RV garage has a 4" floor with rebar and woven-wire reinforcement. Nothing will prevent concrete from cracking, regardless of who is telling, rebar and wire prevent the cracks from jutting up or down, or pulling apart.
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Old 05-20-2014, 06:16 PM   #5
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I just finished the building today 48x24 with 15 foot ceiling. The door is 14x14. It will have 50amp service and sewer and water. Water will be off in winter because I don't think I will ever heat the building. I have another garage that is heated for everything but working on the motorhome. When they finished having the site prepared the contractor told me not to pour the concrete for 6 months. There was a lot of fill and they want it to settle.
The concrete man said he agreed. He also recommended that we pour 5 inches minimum with re-bar and fiber.
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Old 05-20-2014, 06:40 PM   #6
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You may consider doing a 5 in. reinforced and then where the coach sits, doing 6 inch, perhaps an 8'0 x 10'0 for the rear axels and 4'0 x 10'0 area for the front axels sit. Fiber filling as well.
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Old 05-20-2014, 09:25 PM   #7
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Interior walls. I covered the walls of my workshop with 1/4" thick 4x8 sheets of pegboard. Already primed so did not even have to paint. Looks good, store/hang stuff anywhere, and installed with screws so when I want to do an electrical change its easy to open up the wall.
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Old 05-20-2014, 09:53 PM   #8
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Several factors should be considered when building a concrete slab supporting heavy loads:
Quality of concrete mix, recommend at least 3000 psi, 6 sack mix.
Reinforce the slab with reinforcing bars, either #3 or #4 spaced 12" or 18" apart.
Thickness, either 4" or 6", recommend 6", but 4" will be OK if base is properly prepared.
Base, recommend a compacted base of aggregate 4" thick, AND compact to 90%. This is same aggregate base used by freeway and highway construction and is available at a very reasonable cost to the public.
Further remove ALL organic material at least 12" deep under the slab and compact original soil to 90%, and then install the aggregate base and then the concrete slab.
Install construction joints or deep tool joints at 20 ft. maximum in each direction.
You concrete will probably have some temperature cracks, but you will not have structural cracks.
I have designed many concrete slabs for service facilities, including truck shops and bus terminals.
Preparation of the original ground; installation and compaction of base and sub-base are the most important part of the construction process. Do not skimp on this part! If your base fails, the concrete will have structural or differential, offset cracks.
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Old 05-23-2014, 04:15 PM   #9
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Done correctly 4", 4000 psi mix is all you need. The thickness of the pour is just one factor. (40 years experience)
Also done correctly the concrete will not crack.
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Old 05-23-2014, 05:57 PM   #10
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X2 on the base spend the money for this wort every penny I've done dirt work for 25 years it's all in the prep...
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Old 05-23-2014, 06:17 PM   #11
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I built mine myself and used 8" crushed limestone for my base prep. I compacted it with a 84" vibratory compactor. I topped it with 2" of washed gravel to keep it from tracking until I pour the concrete this year in the Fall. I could get by with 4" concrete but for the meager cost difference, i will go with 6" and #4 on 18" center.
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Old 05-24-2014, 02:14 PM   #12
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I had mine done 6" minimum and 3500psi concrete. I did the driveway the same. Here, in Florida, they don't do crushed rock bases, in fact, they pour on the sand. They do the same with houses.

One thing to consider. If you will be putting your coach on jacks for service realized that with jacks alone the pressure on jack base far exceeds that displaced on your tires. This is especially true when putting a tag axle coach on jacks. One jack's floor space is far less than the 3 tires being lifted.
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Old 05-26-2014, 06:06 PM   #13
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I just needed shade and rain protection, so I had one of the steel carports installed. Gable roof with 12' legs. I put down about 3" of limestone rock (Florida sand base). It took about 12 yards to cover my 24X38 area. About $30 a yard delivered and I spread it with a shovel. Over the years, a few compression ruts have formed where I park, but nothing serious.
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Old 05-26-2014, 06:23 PM   #14
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There is gravel fill under my shop and present pad. My 24,000 pound MH cracked the 4 inch thick pad. I am presently building a MH garage on the same gravel base. They poured it 6 inches with fiber glass and rebar, 10 inch thick within 18 inches of edges.

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