Garage addition stumbles - No footings

[jav]

I'm in the process of trying to improve my existing garage by adding a second story to it. It's an older garage that's an "existing non-conforming use"- which basically means I'm limited with what I can do to it because of zoning laws. I can "add-on", as long as it doesn't increase the conformity and going "up" is OK .

I've run into a snag and I'm hoping someone may have some ideas. The garage is in Massachusetts -so it is a freezing climate. My plan to go up required investigating the foundation and I learned that the garage was built on a shallow monolithic slab which means there's no foundation or footings below the frost line. I'm concerned that putting a second story on this is not going to be allowed.

Any thoughts? And no- tearing it down and rebuilding isn't an option. once it's down- it can't be rebuilt where it is.

 

[Thumper68]

Need to know the particulars of the slab to make a informed suggestion.

 

[LB-1911]

I'm in the process of trying to improve my existing garage by adding a second story to it. It's an older garage that's an "existing non-conforming use"- which basically means I'm limited with what I can do to it because of zoning laws. I can "add-on", as long as it doesn't increase the conformity and going "up" is OK .

I've run into a snag and I'm hoping someone may have some ideas. The garage is in Massachusetts -so it is a freezing climate. My plan to go up required investigating the foundation and I learned that the garage was built on a shallow monolithic slab which means there's no foundation or footings below the frost line. I'm concerned that putting a second story on this is not going to be allowed.

Any thoughts? And no- tearing it down and rebuilding isn't an option. once it's down- it can't be rebuilt where it is.

This might give you an idea
Ron Quinn lifting a 2 car garage to replace the footer.

Jack it up - excavate - form & pour a foundation to properly support the proposed structure.

 

[tlmartin84]

Any signs of settlement over the years?

How thick is the slab?

If it was sufficiently thick, I would just dig out all the way around it, and add the frost protection insulation needed. Here are the requirements.........http://api.viglink.com/api/click?fo...ww.toolbase.org/PDF/DesignGu...dFPSFguide.pdf

This is becoming an accepted way of eliminating deep foundation depths. It would be something discussing with your inspector and or engineer.

 

[tlmartin84]

Another option I would propose would be digging piers at multiple locations under the edges of your slab (to frost depth), placing post in your existing walls to transfer any second story loads down.

Just some thoughts.....

 

[sublimate]

This might give you an idea
Ron Quinn lifting a 2 car garage to replace the footer.

I liked the: "Oops, my fault. I hope nothing crashes. If it does I'm screwed, but I'm insured."

 

[Showkey]

Garage on a slab is normal in many areas ( even in cold weather) when it is not attached to the house.

The added second story ?

 

[iajonesy]

My garage is a 26 x 36 and is 2 stories built on a collard slab. The slab has a 12" x 12" ring all the way around the perimeter and through the center of the slab and the floor is 6" thick. It was all rebared and poured as one slab. Does that make sense? If not give me a shout on a PM.

Mike

 

[Kevin54]

jav....welcome to Garage Journal. I'm assuming the username is for a Javelin possibly? If so....post up the pics.

As far as your garage, without knowing how it was built, other than a slab, is just a crapshoot. How old is the garage, and do you know any of the history of it? Did you have it built, or is it an existing garage that you bought the house and garage?

If you want to add a second story, what about cutting out areas of the existing floor and dropping post in for support. I'm assuming that the outside size is maximum you can go, but going inside, and dropping post down, would you be permitted to do that, then add a second story using the post AND existing garage for support. THat way, neither one nor the other would be bearing the full weight of a second story.

Also around here in Ohio, if you go over 10', it is required to have 2x6 walls. I don't know how your existing garage is built. Do you have any idea as to the slab, and walls, or any pics? We need a tad bit more of info.

 

[volleyball]

This might give you an idea
Ron Quinn lifting a 2 car garage to replace the footer.

Jack it up - excavate - form & pour a foundation to properly support the proposed structure.

That guy did the lifting the hard way. Since he was doing the whole perimeter, he should of just cribbed, braced and lifted the garage on the inside slab.

My friend had a much more modern garage and because it was on slab, he was only allowed a partial second story.
Putting a new below frostline footing should be allowed. Just build it to support two stories.
To keep a garage grandfathered in, you need to keep at least one side. The jurisdiction may not only allow you to build two stories, you may be able to stretch the footprint a little bit.

 

[jav]

Wow- lots of responses. I'll fill in some gaps and sorry to say JAV is not for javelin although I'm a fan and I'd love an AMX some day.

The garage age is unknown. I've known the property for over 40 years and it's always been there. The house was built the 1920's but since the house is field stone foundation, I presume the garage was built later.

The slab appears to be 14-16" thick around the perimeter. I've had occasion to drill the center for some anchors and it's at least 4-5" thick as I didn't break through- but highly doubt it's as thick as the perimeter. The slab is prefect. Not a single crack anywhere. The walls are typical 8x8x16 block (could be cinder??? drills dark grey??) and the blocks are set on top of the slab. I don't know if any are filled. Not a hint of settling or frost heave anywhere.

lifting and digging a full foundation don't seem reasonable and may not be allowed. I checked frost protected slab construction but I think because the garage is unheated - it requires Insulation under the slab... not just vertically on the sides, to be compliant so I think that's out. Sono-tube piers maybe an option. I'll do some research.

 

[CNGsaves]

+1 for Piers and steel I-beams to hold up 2nd story. If you plan it out just right, you might get gantry crane for portion of your lower floor !!

 

[tlmartin84]

What size it?

 

[jav]

the garage is 22x22 and it has a shed attached that is 20x12. I was hoping to widen the sheds 12' width to match the garages 22' and then add the second story above both making the whole structure 42x22- 2 levels

 

[Daniel Dudley]

In MA you will need engineered drawings to build anything like this.

 

[dirttracker18]

I cannot speak to the ability to build a second story in your specific situation but I can tell you that here (much deeper frost than you) a mono slab is common with 18" depths at the exterior. I looked into a second story when I built mine and was able to do so with the same mono slab. I did not end up doing that but the option was there.

So frost issue should not be a worry, especially if the slab is in good shape after this long.

 

[Jlbc212]

Considering that the structure is relatively old and hasn't moved or settled, my guess is the foundation would be adequate to support a second floor. However, you will need to consult with a structural engineer to satisfy the building inspector.

 

[larry4406]

Underpin the critical load bearing locations for the 2nd floor structure.

 

[Apex Structures]

I would build you a new two story building right on top of that slab if it were free from horizontal cracks. Most of the new loads would be all vertical pressure and most local governments will want the slab certified for every ones protection. A typical modern monolithic slab would be very close to the measurements you have listed with steel running horizontal. I would be more concerned with the structural integrity of the first floor walls than I would be with the slab. Wall designs change as well based on what they are supporting.