Suspended Concrete floor with basement storage

[Mskgaragefan]

Thinking of having a two car garage built next to my house.
Ideally the garage would sit at the end of my driveway.
The property slops off as my driveway is elevated. This would provide me much needed shed storage below and a two car garage above...

Thoughts on what type of foundation and cost would be needed to build this?

 

[scottydosnntkno]

You can use standard poured walls and precast tensioned sections that sit on top that you pour your final floor on. We just did some at my friends house, 4car 28x50 garage, approximately 1450sq ft. The panels were about 15k, plus the cost of poured wall over trench footings so about another 5k

 

[05r50]

We recently moved and one of the homes we looked at had a huge garage (guess it could 6-8). Anyway that garage had a full basement under it.

The garage floor was held up with steel beams.

 

[KMinAF]

Google Spancrete

 

[GMCGarage]

Thinking of having a two car garage built next to my house.
Ideally the garage would sit at the end of my driveway.
The property slops off as my driveway is elevated. This would provide me much needed shed storage below and a two car garage above...

Thoughts on what type of foundation and cost would be needed to build this?

I would use a poured wall foundation, and have it provide the lip for your topping slab.

 

[Firebrick43]

Built my composite suspended slab for right at 6$ a square foot. It has in floor heat, the pex tubing is not in that figure.

Used icf walls (6") for the higher strength, insulation, and DIY ease. The only labor is for the finishers of the slab. Foundation cost is going to be dependent to on local soils.

 

[willymakeit]

Make sure you account for slab thickness on top of prestress spans. They have camber in them and can interfere with drains(floor) or slope needed. Communicate with the designer where penetrations are wanted to avoid cables.
Make sure your subs are familiar with these structures to avoid issues.

 

[joes169]

We work with pre-cast (Spancrete) panels on a regular basis, and they would be my first choice through my experiences. Cast in place is far more complicated, slower, and far more expensive if you're not going to DIY it, IMPO.

The one thing you have to keep in mind is that the upper floor is more than a floor, as it needs to be treated as a roof, if you want the whole system to work out in the end. W/o a decent rubber membrane or alternative water control option,you will be fighting an uphill battle for the remainder of the life of the structure.......

 

[ard]

The one thing you have to keep in mind is that the upper floor is more than a floor, as it needs to be treated as a roof, if you want the whole system to work out in the end. W/o a decent rubber membrane or alternative water control option,you will be fighting an uphill battle for the remainder of the life of the structure.......

So you mean controlling run off water from the garage floor into the storage area below??

 

[ishiboo]

Spancrete is one manufacturer, but you will need to find whoever is local to you. It's surprisingly affordable - the panels plus delivery/installation for my 3-car are only $16k.

 

[matt_i]

They built one of these 2 doors down from my brother's house and I thought it was the greatest thing I've ever seen.

But, with time gone by I think there are some tradeoffs.
- my opinion is it should be waterproofed as well as the best basement otherwise its going to be a forever source of moisture percolating in thru the soil.
- I think it needs to be insulated, ideally with ICF and eps under the slab, as the R=1 value all over thru concrete is going to **** loads of heat out of it. While it will self-maintain as non-freezing it could potentially have the thermal mass of a stone dungeon.
- water management from above is going to be very important. In a snowy climate parking cars inside I would be worried about chloride attack on the span-floor over long periods of time. It could affect any concrete, but the fact that its a "stressed ceiling" would concern me more.
- any kind of hydrocarbon leaks from above is going to go down. I would think a fresh-air exchanger would be helpful.
- I think it would be more expensive to wire, everything in conduit surface mounted...

I think in the end it would be more expensive from a square footage proposition, but might work on a lot or sub where there's no other way to build a separate building.

 

[850xpeps]

We would use a hollowcore precast floor that has pretentioned cable inside. Then pour a 2” topping and slope as you require to a drain. You can put a hole in one of the hollows and run your drain pipe to an edge from the center. But like said contact a concrete plant. They are usually the ones that engineer and make these panels.

 

[Northislander]

Here's a link to a suspended garage build i am currently working on.
Sorry i haven't been updating my progress
https://www.garagejournal.com/forum/showthread.php?t=374836

 

[joes169]

So you mean controlling run off water from the garage floor into the storage area below??

It's more than just controlling the floor water, you really need to ensure that the front of the planks are sealed off below grade as well. I've seen quite a few plank floors that were taking on water inside the cores, generally from the OH door side, where the driveway meets the garage floor.