Putting a basement under my garage (& back yard) ?

[someguy11]

We have a large, newish (2008) house on a 50x120 inner city corner lot.

In the back yard, facing the alley, is a 22x31 garage with 9 foot ceiling, 5/12 roof. I've added storage in the loft. Stucco exterior.

I have a lot of tools. I'm constantly building things. I need more "man" space.

I'm thinking about (early planning stages) putting a basement under the garage and probably the whole back yard, thus connecting it to the house.

The back of our house is 37 feet wide. The house is about 22 feet from the garage. I could add about 1400 square feet (35 x 40) of man cave, maybe more. I'd probably use some of the space for "fun", but the rest would be solely used for shop purposes.

I'm thinking 9 foot ceiling, ICF construction. I think we'd still want grass over the top of the underground portion of the basement. I'd put a lift between the basement and the garage main floor so that I could move things (table saw, small lathe, etc.), between floors as needed.

I just came back from a planning meeting with the city. They've seen several of these built and they don't have a problem with it, subject to meeting some of their building codes.

Thoughts, ideas, advice ?

 

[Vegaman_Dan]

Ground water, heating and cooling, and huge massive costs.

Is it worth it? If you are hard set on living there and are willing to spend the money, then yes.

If you want to do this affordably, it would be far simpler and cheaper to build all new with that in mind from the start.

It will be a unique property to sell later, though I'm not sure it will have much more property value and many would see it as a liability. This may affect the resale value.

Is it a cool idea? Hell yeah. I wish I could dig a hole in my back yard and just add storage like that.

 

[someguy11]

Ground water: is not a problem, though the floor may actually be below the elevation of the sewer line and thus I may need a sewage lift pump. I'm working with a designer and he says it not a big deal.

Heating: the house has boiler heat and we like it. Actually, we love it, especially in the basement. I think I'd put hydronic heating pipe (PEX hose) in the basement floor and heat it that way. Not sure I would heat the garage main floor. Could always run a simple natgas force air furnace. Pretty simple, efficient and relatively cheap.

Cooling: not sure it would need it. We live far enough north that our summers are shorter and not extremely hot. Actually, I think the basement would stay very nice and cool.

Huge massive costs: Not sure about this. I'm still running the numbers. I'd be the general contractor and manage most or all of the work myself.

Resale value: I've discussed it with several realtors and they love the idea. Our house is pretty high end. They said there are lots of guys that want or need to live inner city but also want lots of man cave room. The basement could be used for just about anything. It would make it a very unique property.

We aren't going to move for the next 20 years anyway. Famous last words ?

 

[joes169]

How do you plan to support the garage in the mean time?

I've been involved in a number of underpin's in my career, as well as garages with basements under them, and your biggest challenges are going to be the small lot size you're dealing with, and your existing garage "being in the way".....

 

[oldearthworm]

I LOVE this concept .. basements simply need ventilation as they are cool in the winter and cool in the summer .. without any added heat ! This will be rather expensive .. building on a sloped properly sized lot would be much easier and far less expensive ..but the lot price could be a killer ..

 

[tatra]

I like your thinking. Thought of doing the same thing myself as I have a similar lot , etc.

 

[thewatusi]

I suggest that you definitely do it.

Take lots of pictures and post them.

 

[someguy11]

How do you plan to support the garage in the mean time?

I've been involved in a number of underpin's in my career, as well as garages with basements under them, and your biggest challenges are going to be the small lot size you're dealing with, and your existing garage "being in the way".....

You are exactly right. I think this is the hardest part of the project. I've been planning it in my mind since we bought the house, 2 years ago.

I thought about selling the garage, but 1) I can't get much for it 2) its impossible to get out the back alley, 3) the replacement cost is surprisingly high, especially when one considers its demolition cost.

To do the project, we'll dig a ramp alongside the garage and then excavate between the house and the garage. We'll have to do this with a skid steer, taking each bucketful right out OR back a trailer down the ramp and load it in the hole. Once the area between the garage and the house is down to level, we'll prop up the garage and excavate under it.

It would obviously be WAY easier to excavate the hole with an excavator if the garage wasn't there. But I just can't justify demolishing the garage and rebuilding it to save money on the excavation. Excavating with the skid steer will be slow, but it will save money in the long run.

It helps that the garage isn't insulated or sheetrocked. Its not as heavy.

Lifting the garage and propping it will be the biggest chore.

We'll use ICF for the foundation because if we go close to the property line, there won't be much room to work outside the foundation.

We'll need to use a cement pump to fill the forms.

Cribbing and pouring the suspended floor will be fun. I have a structural engineer starting to work on the details for me.

I'd use precast floor panels, but I can't figure out a way to put them in place. A crane would have to reach right over the garage.

There will be a beam and posts down the middle of the space. I can live with that.

This is a dynamic project. The details are changing as I learn and go. I'm hoping to do lots of planning and have the project go well when I do it.

I'd like to do the project in the fall of 2015, but that is contingent on a business deal going through, getting enough time and getting the building permit in place before then. I don't want to do it in the spring, so if I don't make the fall 2015 deadline, it will be fall 2016.

 

[someguy11]

As far as cost goes, one can break down the process like this.

1) excavation
2) pouring the footings and walls
3) pouring the basement floor
4) pouring the suspended floor (4 and 5 may be reversed)
5) setting the garage back down in place
6) finishing its interior
7) re landscaping

The only component that is any different from doing a house foundation is the suspended floor. I'm hoping we can pour it in sections so that we can reuse cribbing.

I'm not sure why people keep saying it will be expensive or what expensive would be.

The excavation would be expensive if I hired a contractor, but if I buy a skid steer and run it myself, we should be able to keep the costs down. If I can get a 1 minute cycle time and the skid steer bucket gets out 3/4 of a banked yard, that would be under 900 cycles or 15 hours. Even if it was 40 hours, it wouldn't be bad.

Forming footings is pretty straight forward. As is setting up and pouring ICF walls. I know a couple guys who just did a 2 story house in ICF.

Pouring the basement floor is pretty straight forward.

Thus far everything is a lot of work, but do able. My structural engineer will oversee our work from time to time to make sure we don't screw anything up.

Cribbing and pouring the suspended floor is going to be a huge undertaking. This is the big unknown as far as I am concerned.

 

[readhead]

I recently a worked on a new house built this way. The house is on a small in town lot. By building the house with a detached garage they were able to meet the lot coverage requirements. The basement extends from completely under the garage to under the house. The garage is about fifteen feet away from the house. The basement actually has more square footage than the rest of the house.

The construction is pretty typical with the only main difference being that we put a system of beams and steel decking for the garage floor and connecting section to the house. On the section between the garage and the house a 4" slab was poured then water proofed then a second 4" slab was poured on top. That slab was exposed but could be covered with dirt and grass.

The house turned out great and had way more footage than would have been allowed normally. Plus you could go from the house to the detached garage and never go outside.

 

[Kaizen]

can t imagine it would be worth the cost. yeah it can be done but what 100grand? a lot easier to rent space someplace. cool idea but pretty much a bomb shelter. sorry the costs and complexity just don't warrant it. have you drilled test holes yet? where are you located? ledge? sounds like your dead set on doing it

 

[Radix2]

what kind of a foundation is under the garage presently ?

slab/full frostwall?

I'm not really picturing how you can safely excavate under the building while supporting it far enough out not to be a collapse hazard - is there any space at all such that you could temporarily move the garage, and then move it back ?

 

[someguy11]

can t imagine it would be worth the cost. yeah it can be done but what 100grand? a lot easier to rent space someplace.

Nope, it absolutely isn't cheaper to rent space somewhere.

I was renting 2 10x20 storage bays for storing business stuff. Cost me $700 a month, insurance wouldn't cover the contents, stuff got dusty, there was very limited lighting in the space if you needed to get at something at night and its a PIA to have to drive somewhere every time you need something. Plus you can't work in storage space.

And real, commercial use space costs twice or 3x psf what storage bays cost.

Over the years of running businesses I could have paid for a basement under a garage many times over from what I paid for renting storage space. I should have done something like this many years ago.

 

[someguy11]

I recently a worked on a new house built this way. The house is on a small in town lot. By building the house with a detached garage they were able to meet the lot coverage requirements. The basement extends from completely under the garage to under the house. The garage is about fifteen feet away from the house. The basement actually has more square footage than the rest of the house.

The construction is pretty typical with the only main difference being that we put a system of beams and steel decking for the garage floor and connecting section to the house. On the section between the garage and the house a 4" slab was poured then water proofed then a second 4" slab was poured on top. That slab was exposed but could be covered with dirt and grass.

The house turned out great and had way more footage than would have been allowed normally. Plus you could go from the house to the detached garage and never go outside.

Do you have any pictures of this under construction ?

 

[someguy11]

what kind of a foundation is under the garage presently ?

slab/full frostwall?

Yes.

I'm not really picturing how you can safely excavate under the building while supporting it far enough out not to be a collapse hazard - is there any space at all such that you could temporarily move the garage, and then move it back ?

No space to temporarily move it, unless we moved it back tight against the house and did 1/2 the basement and then moved it on that and did the other half, and even then we would be working under the garage some of the time.

 

[little d]

My Dad, Brother and I have been involved in a coupla projects like this, the first was digging a cellar under an existing house and the second was a fire re-mod on a restaurant.

On the digging part, unless you are doing it yourself and have all the time in the world, move the shop so you can get the equipment in there to get the job done. Working under a building can be done but is a HUGE pain in the ***.

On the suspended floor, you can use pre-cast panels but wouldn't it be easier to pump the concrete over the garage then lift the panels over? When we did the floor on the restaurant (the first time I had done a self supporting concrete floor), I was as nervous as a ***** in church. The Engineer on the project sensing this came up to me and said, don't worry, I do parking garages all the time and that floor would support it's self with out the supports you have under it, I hadn't even thought of them when we were setting everything for the pour and he was right, after it set up and we sat the equipment in there (and we are talking heavy equipment), that floor was as solid as if it was a slab on the ground .

Please do a build and post up lots of pics, I love challenging projects like this,
D

 

[readhead]

No pictures. We do steel and concrete garage floors in new construction quite often. A lot of times it is cheaper to do a suspended floor and have useable space underneath than backfilling ten feet just to pour a slab. As for digging under the garage, when I lived in Telluride this was a common occurrence. The lots are very small. A house mover was brought in to jack up the house. The excavation and foundation was done, then the house was lowered back down. Lifting a garage without a floor is a little more work but totally doable.

 

[BDAZSVT]

I like the idea but cannot imagine the cost. Here is a similar concept. http://www.garagejournal.com/forum/showthread.php?t=12234

 

[someguy11]

Thanks for the replies.

Lets say this project did cost $100K. Lets say it yields 1500 ft^2 of usable space. That is $66/ft^2, including land cost.

An insulated garage without land costs $40-$50K for 6-700 ft^2, so the costs aren't much different.

 

[Mxrcr]

Don't rule out the prestressed panels for the garage. If you coordinate the cribbing to allow the panels to go in from the alley side you could use a lull to place the panels instead of a crane, thus keeping them under the cribbed garage. You may have to set and slide a few panels depending on panel weight and lull size, but with the proper logistics easily accomplished. Panels would eliminate a ton of work and should eliminate the support beam. Not sure if this would work for you, but just a thought. A few pics of the lot layout would definitely help us get a visual of your plans. This sounds like an awesome project.

 

[CNGsaves]

Sounds like "perfect" garage !! It's how ALL garages s/b built !! I'd love for my garage to have a full basement under it, and tunnel walkway the short 10 ft to the house. The breezeway between would be great place for elevator as right next to driveway.

OP . . Curious where the "elevator" can be and still meet code for any potential flammable vapors that might seep into the underground "live-able" space??

Also, where is "north" . . . is that north Canada, north Florida, or north USA !!

Update GJ Profile with location.

Looking forward to this build . . . sounds awesome.

 

[tfi racing]

I like it,if you can pay for it,why not?Since you have back alley access,why not jack up the garage and support it,break out the existing slab and footings,then dig out all the way from the alley to the house with a mini-hoe and bobcat?Looks like the excavating with the existing garage in the way will be your biggest challenge,once that is done the rest is relatively simple.

 

[James-W]

Personally, I wouldn't do it, but if you feel it is something you really want to do, then I say do it and I wish you all the best with the project.

 

[softailgarage]

Why not just do the shop underground? A couple of years ago a member did exactly that but it cost him a buttload, somewhere around 500k if I remember right.

EDIT: I just saw the post regarding the "Bunker Garage" , that was the thread. You'll notice he had deleted alot of his replys, this because somebody was trying to figure out where he lived by his replys, which made the OP paranoid, so he deleted them ( I don't blame him, I would have done the same)

 

[someguy11]

I think pre stressed panels are out because there is no way to place them.

On one side is the neighbors yard. On the other side is a row of 30-40' evergreen trees. On another side is the house. The easiest way to place them would be over the garage from the alley. Its 15ish feet tall to the peak. But a crane large enough to hoist a panel over the garage won't fit in the alley and the alley has a power line on the other side from the garage entrance. Its tight.

But we can get a concrete pumper truck in there.

 

[bczygan]

You are way, way ahead of yourself.

Your first step is finding out your zoning and looking at all the zoning regulations.

Have you done that yet?

 

[ez-duzit]

...I have a lot of tools. I'm constantly building things...

...I'd be the general contractor and manage most or all of the work myself...

Wondering if you are aware of the difference between "I'm constantly building things." and "I'd be the general contractor (on a complex and costly construction project I've never done before)."

Then there's the whole basement-under-a-garage-with-a-lift. And all those shenanigans necessary to work around the existing garage while excavating UNDER it! Come on!

Duck said $200k. Bet he's close.

 

[Cobra5150]

...

Duck said $200k. Bet he's close.

If not low. I'd say over $200K.

 

[James-W]

Obviously, the final cost will be determined by how much he can do himself and by how much he has to hire out. But I suspect that in any case the final cost is going to be very high.

 

[nickelmore]

Great idea...I have always wanted to do something like it but have never had the opportunity.

My plan is to use pre stress panels and have a "drive out basement" for all my wheeled yard toys.

Most oil change places use pre stress panels for the floor. You need to have them made according to plans so you can have raceways and acess panels for stairs.

 

[DC73]

You are way, way ahead of yourself.

Your first step is finding out your zoning and looking at all the zoning regulations.

Have you done that yet?

From Post #1:

I just came back from a planning meeting with the city. They've seen several of these built and they don't have a problem with it, subject to meeting some of their building codes.

Someguy11 - don't let the naysayers get to you. This is a great project and you're going about it the right way. The more you can do yourself, the less it will cost. Document everything about the project and post all the cool photos when its done.

Good luck.

DC

 

[someguy11]

You are way, way ahead of yourself.

Your first step is finding out your zoning and looking at all the zoning regulations.

Have you done that yet?

Yep. Read the OP.

 

[fourjeepin]

Can you post up pics of the lot? Sounds like a super cool build

 

[nick2010tundra]

Fun post to watch, half the guys begging him to do it, the other half screaming at him to not do it. Hey its your money and it sounds like you have an expensive lot and it may be worth it.

They put a man on the moon, I'm pretty sure you can build a basement garage, although I would price the difference of just tearing down the old garage and starting over. By the time you support the structure and all the bull of trying to work around it, it may be cheaper to tear it down, do all the work and build your new dream garage.

Also have you thought about going up, maybe a lift to a second floor, if your spending all the money I would be looking into doing a 2 story with that basement

 

[readhead]

Lifting a building and putting a new foundation under it is nothing new. It's being done every day all around the country. Would it be possible to move the garage and store it untill the work is done and then bring it back?

 

[theoldwizard1]

An out of the box approach, that may not be do-able.

Dig the "side" foundation for the new basement (in front of the garage), but do NOT remove the dirt in the middle. Once the foundation is built and poured (good decision to use ICFs), move the garage forward and temporarily locate over the new new basement.

Remove the garage floor and an existing foundation. As you dig the new basement under where the garage was, an excavator and a skid steering can excavate under where the garage is temporarily located.



I have lived in a tri-level home for over 35 year. Dozens and dozens of times I have dreamed about digging a basement under the front half of the house (concrete crawl space). Cost killed it every time. Digging a basement under is not uncommon in SE MI. They are sometimes called a "Michigan Basement".

 

[someguy11]

Fun post to watch, half the guys begging him to do it, the other half screaming at him to not do it. Hey its your money and it sounds like you have an expensive lot and it may be worth it.

They put a man on the moon, I'm pretty sure you can build a basement garage, although I would price the difference of just tearing down the old garage and starting over. By the time you support the structure and all the bull of trying to work around it, it may be cheaper to tear it down, do all the work and build your new dream garage.

I've looked at it. The material package isn't too bad for a basic garage, but its the labor to put it up, especially when stucco is involved. My garage is a bit fancy, it has stone work on the exterior and a fancier roof. I could salvage the stone work, but its quite a bit of work to re install it.

There is no way to get my garage out the back alley. If it comes out, it would have to be demolished and hauled away and that costs $$$$.

The total cost of reusing the garage is that of lifting it up and working around it. Its a bit more work to excavate around it, but its do able.

Also have you thought about going up, maybe a lift to a second floor, if your spending all the money I would be looking into doing a 2 story with that basement

I'd need a "relaxation" to get a permit for a second floor on an "accessory building" in my area. I know this because i looked into it when we were looking at purchasing a different house. They are hard to get and we have a bit of a view from the bedroom window/balcony over the garage right now. I don't want to make the garage any larger or more imposing than it is right now. I love the idea of hiding everything under ground.

 

[someguy11]

An out of the box approach, that may not be do-able.

Dig the "side" foundation for the new basement (in front of the garage), but do NOT remove the dirt in the middle. Once the foundation is built and poured (good decision to use ICFs), move the garage forward and temporarily locate over the new new basement.

Remove the garage floor and an existing foundation. As you dig the new basement under where the garage was, an excavator and a skid steering can excavate under where the garage is temporarily located.

I've thought about leaving the middle dirt in while building the foundation. Much easier to support the garage while working in the basement. If we can lift the garage and work under it, we can probably do the wall pour in one go. That may be necessary, I'm not sure at this point.

I have lived in a tri-level home for over 35 year. Dozens and dozens of times I have dreamed about digging a basement under the front half of the house (concrete crawl space). Cost killed it every time. Digging a basement under is not uncommon in SE MI. They are sometimes called a "Michigan Basement".

We own a 1913 revenue property, it's a house. The basement was put in after the fact, so it can be done. The house next to our rental property has no basement, only a hole that the furnace sits in. The entire house sits on timbers. Very creepy down there.

 

[someguy11]

Lifting a building and putting a new foundation under it is nothing new. It's being done every day all around the country. Would it be possible to move the garage and store it untill the work is done and then bring it back?

Nope. Can't get it out the back alley. Not really enough room in the back yard.

 

[someguy11]

Miscellaneous Ramblings

Let me emphasize that this project is in the early phases. I'll make a go/no go decision for the fall of 2015 in early July. Excavation would start in September. In the mean time I'm working on it casually, learning all I can, planning, pricing, etc. The permitting phase will take about 8 weeks. My designer has some of the plans done, but they need to be refreshed.

We need to tie in the landscape design of the back yard with the bunker build. The back yard will be different if we put grass on top of the bunker roof versus have a mostly concrete (tile) backyard. One idea is to build a mock European courtyard in the back yard. This has to be decided prior to the build, as it affects the height of the roof and floor.

We will also be tying the landscaping of the front yard with the bunker build. The yard in the front of the house is relatively unused and has a 6 foot slope down to the street. We want to use some of the dirt excavated from the basement hole to fill in the front yard, probably with terraced retaining walls down to the street. That will allow us to put a sitting area/patio on the front of the house.

I'm going to buy a used skid steer loader for the project and do all the earth work myself. I landscaped the side yard last summer and it turned out very well. We get lots of comments on it. We worked with an experienced landscape designer on that project.

We also need to tie the finishing of the basement into the bunker. Right now the basement is finished to a high standard with 2 bedrooms, a large bathroom, fitness room and an "unfinished" media room. Right now the plan is to flip the bathroom, which sits between the two bedrooms, creating a 4 foot hallway to get to the bunker door in the house foundation.

The media room is "unfinished" because the house is open concept and sound travels very easily from the media room to the main floor via the staircase. We need to close off the media room from the open area, something we'll do once we figure out exactly how we'd use the space in the bunker. One thought is to move (and enlarge) the fitness room another is to move the media room into the bunker, but that would create a big room for which we have not much use in the basement... lots to think about here.

I mainly want to use the bunker for shop space and free up the entire garage for parking vehicles. I don't want to do any smelly work in the bunker. I might store dirt bikes down there, but I won't service them or start them up down there. I'd do all my welding on the main floor of the garage as well. I might do wood working in the basement and maybe a bit of machining. I have a lathe and mill.

Having said that I want the bunker space for storage, I DO NOT want to become a pack rat. Its not to be junk storage space. If I don't use something regularly or have a specific project with a timeline planned for something, I try to sell it.

I find that its fairly easy to do these sorts of projects if you hire an experienced designer. We renovated the interior of the house and used an experienced interior/structural designer. It turned out great, at a fraction of the cost of hiring someone to do a turn key renovation. Lots of work though. It takes some balls to tear apart a recently built house (2008), but the results were totally worth it.

I don't need to finish the bunker space right away. It might be bare concrete until I finish the landscaping and tying in the basement. I'd probably tie in the basement during the winter of 2015/2016, finish the landscaping in the spring of 2016 and finish the bunker interior in the winter of 2016/2017.

Having said that, I'm not sure what exactly I would finish in the bunker, other than to finish it like a garage. Obviously if we moved the fitness room into the bunker, that would be divided out from the shop space, but not sure what else would require its own space.

FWIW, we are presently planning to put 2 large windows in window wells in the house side of the bunker. I want them for ventilation, to allow a bit of light into the bunker and for emergency egress, should it be necessary.

This whole project might never be realized. For now its interesting to have this discussion and work on the details. We have the funds to build this thing, but I can't justify it as a necessity. If my business deal comes through, we'll have a surplus that I would feel much better about spending on a "nice to have", which is what I consider this project. I'm a bit conservative when it comes to spending money.

We intend to stay in this house for the next 20-25 years. It can't really be beat for location, comfort, etc. Adding the bunker and the rest of the work would take it from a "B+" house in our minds to an "A+" house.