Underground garage extension

[oldcrewcoach9102]

Hi All: This is my first post and I am looking for some advice. I am not a builder or really handy at all, just looking to improve my home. Right now we have a 2 car garage under the house (basement level). I am wondering if we could make this a bigger garage by excavating thru the back wall and under the front patio area of the house. The roof of the garage would be underground and below the front entrance of the house. (It is a ranch built on a slope with full exposure on the side where the garage door is.) Has anyone done something like this? Thoughts....I am not sure if this is clear enough....

 

[bczygan]

Sure. Welcome to GJ.

What is the basement wall structure? Block with steel reinforcing? Poured concrete with steel reinforcing? A bit of work to demolish. And new work will need excavation, drainage, new reinforced basement walls with footings, waterproofing, insulation and slab, back-fill and a load bearing roof, designed to support the patio. Is there access for heavy excavation equipment? If you want a large opening between existing and new spaces you will need substantial beams to support the loads, especially from the new engineered roof that supports the patio.

What is the elevation of the ceiling in the basement? And the clear basement height? Typically, the ceiling of the basement will be above grade, so an extension will be above grade.

 

[rburke65]

Welcome from Ohio!

 

[oldcrewcoach9102]

Oh...you are good! Lots to think about here. The garage wall/basement foundation is poured concrete. ANd yes, there is easy access for heavy equipment. The opening would need to be only a one car garage size, but would need a big beam for sure. What would the ceiling be made of? Concrete? Do you have ANY idea how much something like this would cost ....in Wisconsin?

 

[Hawk]

My advice would run toward saying, Check with an engineer.

 

[Always_Thinkin]

Do you have pictures of the entrance to the garage and the lay of the land around you house? There is a home here in my town that has a two car garage out the rear of the house. Then the roof of the garage is a reinforced concrete slab that the first story walks out on and serves as a nice big elevated patio.

 

[bigbubba]

Do you have pictures of the entrance to the garage and the lay of the land around you house? There is a home here in my town that has a two car garage out the rear of the house. Then the roof of the garage is a reinforced concrete slab that the firdt dtory walks out on and serves as a nice big elevated patio.

One built like that a few houses over from me as well.Pretty slick setup!

 

[bczygan]

Oh...you are good! Lots to think about here. The garage wall/basement foundation is poured concrete. ANd yes, there is easy access for heavy equipment. The opening would need to be only a one car garage size, but would need a big beam for sure. What would the ceiling be made of? Concrete? Do you have ANY idea how much something like this would cost ....in Wisconsin?

Typically, basement space is the cheapest space built in a house. But demo and excavation for an existing house and providing a load bearing roof will make this more expensive space. Do you have space to add on to the existing garage to one side or out the front? That will be less expensive space to add. What is your lot and house layout, setbacks etc.? What use will this extra space be for?

And for pricing...you can't price until you define what you are doing. The better the definition, the more accurate the pricing.

 

[Justanoldguy]

A few pictures would make things a bit clearer if good advise is required.

Welcome aboard by the way.

 

[wssix99]

make this a bigger garage by excavating thru the back wall

This is really expensive. You'd have to shore up the wall, probably install a steel beam across the span to hold up the house above.

and under the front patio area of the house.

This is even more expensive. If its a stoop, you'd have to remove that part of the foundation that supports it and come up with a new structure over the garage to keep it up.

The roof of the garage would be underground and below the front entrance of the house.

This is super expensive. Underground roofs (that keep water out reliably) are heavy duty things.


You might be better off hiring an Architect to come up with some other conceptual solutions to the problem for your particular site. A few hundred dollars invested in an architect to come up with conceptual designs could save you tens of thousands of dollars building something like the underground garage.

 

[sberry]

Lets get right to the point, how much money do you have and how bad do you want it?

 

[geotek]

It's a mini "Bunker Garage" in the making! I like the idea and agree to check with an architect or engineer. I think that will mostly be for supporing the opening, the rest should be relatively easy once the house is supported over the opening. A concrete saw will make short work of your basement wall once you've moved all the dirt and have the house supported.

 

[rsanter]

You can do it
You will use either block or poured concrete for the walls. I recommend you use poured concrete ICF walls. You will use concrete for the roof/ceiling and may need a couple steel beams depending on a couple of factors.
You will use a waterproof membrane on top of the concrete roof or water will seep through
Cost...I have no idea

What about going to the back of the house?
What about a separate garage?

Bob

 

[KMinAF]

Google spancrete

 

[CNGsaves]

Gotta SEE what you are starting with now . . . . let's see pics !!