Need ideas on this ADU pop top project.

[DoubleStud]

So the plan was to build a living space over the existing garage with lower roof carport. Then architect changed it to this graphic below where the addition is now over the carport, and you have low roof space over the garage for storage. But then it has been discovered that the existing garage was not built to frost depth. The architect talked to the building department and he said we should not put the floor framing on top of the garage. He suggested adding 3 more columns somehow rely on the existing garage to resist lateral. This is starting to not make sense and way different than what I bid on. Do you have any ideas what I could do?

 

[jayrod12]

Run? If the architect can't understand that the two building shouldn't be connected, then I'm not sure what else you can do.

You could talk him into bracing between the columns in one direction and maybe turning them into moment frames in the other, provide a movement joint between the garage and the living space.

 

[phamENG]

Gross.

How far above frost depth are the garage footings? Underpinning that and going back to the original design may make more sense and be less expensive in the long run.

Either way, be sure to inform the architect NOW that the architectural design has changed and you'll be providing a new proposal reflecting the additional work that will be required.

 

[KootK]

Long shot but could you do shallow frost protection on the garage? May not be cheap if you'll have to demo concrete flatwork in the area.

 

[DoubleStud]

Thanks everyone. We will know more about the existing foundation this weekend. This is the architect's property he just bought. He will dig this weekend. Building department told him it is more than likely not frost depth.

 

[JAE]

Yes yes - do what KootK suggests. I've done it several times before when frost depth was an issue (i.e. a client wanted to dig down next to their building to form a truck dock).

 

[XR250]

Doesn't that only work if the garage is heated?
Is there any signs that frost heave has ever occured? I imagine the slab would be cracked if it had.

 

[KootK]

Doesn't that only work if the garage is heated?

Yup. If the ADU will be heated, I think that it would be a good idea to heat the garage anyhow. Otherwise you'll just be hemorrhaging heat out the bottom of the ADU.