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Question DetailsAsked on 3/14/2013

Need to increase RV door height from 10 feet to 11 feet. Floor slab is currently same level as car garage floor. Can floor slab be lower?

My Motorhome garage ceiling is about 18 inches about the door opening. The door opener takes up most of this space. Because the outside foundation of the motorhome bay & the foundation between the car garage and the motorhome bay is cinderblock, I feel excavating down and pouring new slab would be the way to go. What you say?

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2 Answers


Call a structural engineer for an opinion. Without seeing it firsthand it's all speculation. Even seeing it myself I'd have an engineer called in. You don't want to destroy the integrity of the structure by demolishing a portion of it. It may be cheaper to build a new, separate structure by the time all of the modifications and reinforcements are made.

Answered 7 years ago by Todd's Home Services


Came across this looking at other driveway issues - here is two bits in case you have not come to a decision on this.

To do it economically, it all comes down to your concrete foundation depth. If the top of the concrete footing (not the cinder block) is more than about 18-20 inches (12 inch floor lowering plus 6-8 inch slab thickness) below the current top of slab elevation, you have a shot at it.

To get a first feeling for this, try digging down outside the garage as close to the RV bay slab as you reasonably can, and see if you have cinder block or concrete 18-20" below slab level. If concrete, then a major structural modification - doable but probably more than you want to spend (thousands PLUS slab remove/replace cost). If cinder block, you have a chance, but it will depend on what your house slab situation is - if there is not a foundation wall between the house and the garage (under the slabs) then that would be a MAJOR modification, and as Todd said, tacking on another RV bay might be cheaper (especially if it could just be a carport, without deep foundation). If there is a footing under the joint between house and garage slabs, then dropping the garage slab might be a go.

You still need to see a structural engineer, and a small piece of slab along the house side and possibly at the garage door may have to be jackhammered out and a test pit dug to be sure it will work.

Either way, remove and replace garage slab could cost (assuming 12x30' bay) probably $3-5,000 depending on structural concrete mods needed, and whether furnace or hot water heater has to be retained and a concrete pedestal built for them to stay where they are.

Answered 6 years ago by LCD

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