Suspended Garage Floor

[507caddy]

Moving soon to a new house, garage is 33x23, three bay across.
Finally have a ceiling that is ~11.5' high....
But..
It is a suspended slab, great for storage below, accessed through the walk out basement.
I have always wanted a lift and am wondering if a 4 post would work for me.
Obviously I need to talk to the engineer but has this been done.
The slab has not been poured yet.
It is basically a plywood floor sitting on three walls resting on footings in the basement.

 

[danfromsyr]

I have no idea but a car on a lift is only as heavy as the car+lift weight
meaning that say a 4dr sedan+lift would weight similar to a 4dr 4x4 truck w/o the lift..
so can it support a F350 diesel ?
so what is the # sq ft/in rating of the floor deck?

 

[mike93lx]

I'm confused. You say it is a suspended slab, but it hasn't been poured and it is made out of plywood.

Usually a concrete slab that has space underneath is going to be a tensioned slab, afaik

With a lift, I would think you want to have it spec'd for the weight of the lift, plus two vehicles, not just one.

 

[m6z]

Seems unusual for residential construction, at least around here.

 

[FredWanaker]

makes me think of the show on TV where they were towing a car out of a basement that had a suspended slab, and it failed. Obviously it can be made to work because parking garages do it all the time, but boy would I want the engineer to go over those specs one more time.

Maybe place an I beam directly under where the lift will go and anchor the lift to it somehow thru some steel blocks or something. An engineer should be able to design what will work.

 

[mike93lx]

Seems unusual for residential construction, at least around here.

I have a buddy that used a tensioned slab for his garage as the house was built into a hill and the basement was a walkout. Great application for it

 

[K'ledgeBldr]

I’ve done two houses with this scenario.
Both were I-beam and pan like this-

Suspended Garage Slab from Design-Build Specialists | Steel Concepts

With a suspended garage slab you can have the extra space you need and increase the value of your home at a fraction of the cost, from a name you can trust.

steel-concepts.com

It was all engineered by a structural engineer we had on retainer. I don’t have the foggiest what size the beams were, how much rebar, how thick, etc. it was about a decade ago.

My suggestion is if there is a possibility of using a lift of any type, it should be run-by the engineer so the floor system can be calc’ed.

A more popular option today is precast/pretensioned slab sections that are placed on-site. This is when speed is essential, or site conditions make other means unfavorable.

 

[Renegade1LI]

I'm actually planning something similar, except it will be a supported slab poured in place, it sounds like the plywood the op is talking about is the formed deck. I would speak with the engineer before the new slab is poured, but no reason it can't be designed for what you want. We just built a bus depot all 8" slabs on metal deck supported by I beams, holds a lot of buses so no reason it can't be designed for your needs.

 

[507caddy]

appreciate all the replys

below the garage there are two walls dividing (red lines) the space into 3 "rooms"
these walls hold up rafters, above this is a plywood pan that the slab will be poured into,
no idea about tensioning or anything like that, it was a spec build

not sure on the thickness of the slab

I assume it will hold an F350 diesel so my chevelle + lift + snowmachines + four wheelers should be fine, maybe 8,000lbs

wonder what happens if i get that setup and put my wifes expedition under the car then we are looking at 12,500ish in one space

 

[Renegade1LI]

appreciate all the replys

below the garage there are two wall dividing (red lines) the space into 3 "rooms"
these walls hold up rafters, above this is a plywood pan that the slab will be poured into,
no idea about tensioning or anything like that, it was a spec build

not sure on the thickness of the slab

I assume it will hold an F350 diesel so my chevelle + lift + snowmachines + four wheelers should be fine, maybe 8,000lbs

wonder what happens if i get that setup and put my wifes expedition under the car then we are looking at 12,500ish in one space

Great layout, I always like extra basement storage, would need more info, can you speak to who designed it?

 

[strutaeng]

If this is spec. house, I'm guessing the slab (sounds like the plywood is the form for the slab?) was designed for 40 psf, since that what the code requires. There's also a special load case where there's a point load of like 3,000 lbs on an area of like 4.5"x4.5". IIRC this is simulating a vehicle lifted on a car jack. The special load case is not in addition to the 40 psf though.

I'm not sure if you could still talk to the builder to see if they (designer) can check to see if the slab can handle a lift. They'll probably ask for a lift spec., if they even want to help you out. Probably won't calc. out.

Otherwise, some steel beams can be retrofitted in later under the lift from the basement level. Beams spanning from basement wall to basement wall.

 

[507caddy]

It is still being built so we are talking on a regular basis, I will ask and see what they say, maybe they will be helpful

my realtor (lots of construction experience) suggested i have them pour footings in the basement so beams could be run up and brace directly below the lift pads, probably the simplest thing to do depending on where they hit, I am still trying to maximize the storage below so i do not have a bunch of infrequently used stuff in the garage.

 

[billconner]

so like 30' perpendicular to the walls below, and I'm guessing those are load bearing walls - block or poured? No problem for a reinforced slab poured in place to support your loads. As others have said, have an engineer look at it.

The IRC requires garages to support 50 psf with a footnote "Elevated garage floors shall be capable of supporting a 2,000-pound load applied over a 20-square-inch area." which would seem close to adequate for 4 post lift. I'd still have an engineer check it.

 

[507caddy]

thanks, that is great information,
the inside walls (red lines) are stick built on poured footings, not sure if there was anything else done to them, have not been inside for a while, they have also been completing double shear walls (for earthquake loads?), not sure if these walls were added onto

 

[billconner]

Steel or wood stud walls? No reason not to but have rarely seen slabs supported on wood framed walls.

 

[507caddy]

wood

 

[billconner]

engineer - or the designer to start

 

[walta]

It is still being built so we are talking on a regular basis.

Is the place still drawing on paper?

If not, it seems a little late to be asking now.

You need to ask your questions of the engineer long before the concrete was poured.

The only house I was ever in with a basement under the garage had salty water dripping from the ceiling. I am not saying it can’t be done correctly just that you need to be on top of the details from the start.



Walta

 

[507caddy]

Is the place still drawing on paper?

If not, it seems a little late to be asking now.

You need to ask your questions of the engineer long before the concrete was poured.

The only house I was ever in with a basement under the garage had salty water dripping from the ceiling. I am not saying it can’t be done correctly just that you need to be on top of the details from the start.



Walta

when we bought the place it was already framed, agree with you though
just assumed I would not be getting a lift, then started to think it might be possible.

 

[walta]

when we bought the place it was already framed, agree with you though
just assumed I would not be getting a lift, then started to think it might be possible.

This is starting to sound like a can of worms.

Seems like you need an engineer to inspect and write you a report about what you bought and his opinion of its useability. No not the contractor. No not the building inspector. No not the engineer that approved the plans. Someone without any conflicting interests. Yes it will cost a few thousand but may save you hundreds of thousands.

What was the “story” they told you about why someone walked away from there dream home losing tens of thousands of dollars by do so.

Walta

 

[cvairwerks]

F350 diesel is going to be around 7k pounds by itself. Even a cheap lift that will just pick it up a little is going to be over 1k pounds itself. Need to be a bit more realistic on weights.

 

[507caddy]

This is starting to sound like a can of worms.

Seems like you need an engineer to inspect and write you a report about what you bought and his opinion of its useability. No not the contractor. No not the building inspector. No not the engineer that approved the plans. Someone without any conflicting interests. Yes it will cost a few thousand but may save you hundreds of thousands.

What was the “story” they told you about why someone walked away from there dream home losing tens of thousands of dollars by do so.

Walta

no body walked away, builders here (and a lot of places) will buy a piece of land and subdivide, start building houses and sell as they go, this plan will be built dozens of times

 

[507caddy]

F350 diesel is going to be around 7k pounds by itself. Even a cheap lift that will just pick it up a little is going to be over 1k pounds itself. Need to be a bit more realistic on weights.

I was saying that my Chevelle and a lift will weigh less than a HD type truck....

 

[larry4406]

I’ve done two houses with this scenario.
Both were I-beam and pan like this-

Suspended Garage Slab from Design-Build Specialists | Steel Concepts

With a suspended garage slab you can have the extra space you need and increase the value of your home at a fraction of the cost, from a name you can trust.

steel-concepts.com

It was all engineered by a structural engineer we had on retainer. I don’t have the foggiest what size the beams were, how much rebar, how thick, etc. it was about a decade ago.

My suggestion is if there is a possibility of using a lift of any type, it should be run-by the engineer so the floor system can be calc’ed.

A more popular option today is precast/pretensioned slab sections that are placed on-site. This is when speed is essential, or site conditions make other means unfavorable.

The ones I have done were also metal pans on structural steel beams. The customer had these slabs designed for eventual use of a 4-post lift. These were quite a challenge.

40x40 hillside garage with mezzanine-in progress updates!

Update- this started as a seeking advice thread but the project is now underway and I'm posting updates as I can! Does anyone in VA have any recommendations? Im looking for someone willing and capable to form my garage foundation thats on a steep slope. I will be using Metwood beams and...

www.garagejournal.com

 

[kbs2244]

Have your engineer work out the numbers on a hole in the garage floor
you have a great big pit