Out building foundation for compressor shack.

[600SL]

Hello

I have a question regarding building a shack outside my garage to house my air compressor. The shack will be against the exterior wall of the garage. It will touching the garage but according to the town it cannot be attached to the garage. So I would like to build a pad of some kind that hold this square to the building. The problem I have noticed is that the ground outside the building tends to breath. I notice my generator is perfectly level on some days and then slopes away from the garage on others. So I'm afraid that if I build this shack some days the top will be against the garage and some days it wont. I would like to minimize how much it moves without having to dig down 3 ft.

The shack will look like the picture below except I will not have a large concrete pad to place it on.

 

[mike93lx]

If you want it to stay aligned, the foundation needs to match the shop's depth

 

[600SL]

If you want it to stay aligned, the foundation needs to match the shop's depth

I was afraid of that. That's 42" down.

 

[jack stand]

It sounds like your breathing ground is actually freezing ground. There's no way around digging, at least some.
Investigate "frost protected shallow foundation" and the principles behind this.

 

[kaymccampbell]

Start digging now, you'll be done before the snow flies.

 

[kaymccampbell]

Maybe it'd be cheaper n easier to buy a scroll compressor.

 

[600SL]

It sounds like your breathing ground is actually freezing ground. There's no way around digging, at least some.
Investigate "frost protected shallow foundation" and the principles behind this.

I have never checked it in freezing weather so I don't know about that. I have checked it in the summer dry days vs just after raining and that's when I notice it. Have the same issue with an AC compressor on the house.

 

[carlaisle]

Could be frost heave, could just be expansive soil. The town said the shack couldn't be attached to the garage, but what about the foundation for the shack? Install footings and tie the shack foundation to the garage foundation. Build the shack on top of the shack foundation but leave a gap of X" between the two structures and you have complied with the town's requirement...if they're willing to play along.

 

[600SL]

Could be frost heave, could just be expansive soil. The town said the shack couldn't be attached to the garage, but what about the foundation for the shack? Install footings and tie the shack foundation to the garage foundation. Build the shack on top of the shack foundation but leave a gap of X" between the two structures and you have complied with the town's requirement...if they're willing to play along.

The idea is to not build a foundation, at least any more than a slab.

The idea I'm thinking of now is to put 4 post in the ground down to footing depth and build the enclosure on those 4 posts. Then place the compressor on the ground on top of a concrete pad that can go up and down with the surface. I would like to find some kind of composite post to put into the ground.

 

[mike93lx]

The idea is to not build a foundation, at least any more than a slab.

The idea I'm thinking of now is to put 4 post in the ground down to footing depth and build the enclosure on those 4 posts. Then place the compressor on the ground on top of a concrete pad that can go up and down with the surface. I would like to find some kind of composite post to put into the ground.

Why not just make a platform mounted to the 4x4's and put the compressor on that? Basically a little deck

 

[Ultradog MN]

Hello

I have a question regarding building a shack outside my garage to house my air compressor. The shack will be against the exterior wall of the garage. It will touching the garage but according to the town it cannot be attached to the garage. So I would like to build a pad of some kind that hold this square to the building. The problem I have noticed is that the ground outside the building tends to breath. I notice my generator is perfectly level on some days and then slopes away from the garage on others. So I'm afraid that if I build this shack some days the top will be against the garage and some days it wont. I would like to minimize how much it moves without having to dig down 3 ft.

The shack will look like the picture below except I will not have a large concrete pad to place it on.

Deep footings seem like Massive overkill to me. Compressor don't care if it's a few degrees out of level. I would pour a 4" concrete slab about a foot away from the garage and build your little shed on that.

 

[OccupantRJ]

You may need an open side shelter or good venting for the air compressor depending on the unit. I have an insulated rear shop room that is 8x20 and it gets so hot in there with my true 5 hp compressor running that I installed a through the wall vent fan and louvers controlled by an automatic thermostat to keep the heat down while using the bead blast cabinet.

 

[600SL]

Why not just make a platform mounted to the 4x4's and put the compressor on that? Basically a little deck

I did think about that but was concerned the compressor vibration would drive one or two post into the ground.

 

[mike93lx]

I did think about that but was concerned the compressor vibration would drive one or two post into the ground.

If that was the case, they weren't installed well.

If you go down to the depth you noted, they should be fine.

 

[600SL]

You may need an open side shelter or good venting for the air compressor depending on the unit. I have an insulated rear shop room that is 8x20 and it gets so hot in there with my true 5 hp compressor running that I installed a through the wall vent fan and louvers controlled by an automatic thermostat to keep the heat down while using the bead blast cabinet.

Notice the vent on the side in post #1. There is also soffit vents along the top above the door. That was all I needed. And that shack was insulated for noise. I was running a 3.7 HP lows compressor and doing sand blasting. But I do want to upgrade to a true 5HP.

 

[600SL]

If that was the case, they weren't installed well.

If you go down to the depth you noted, they should be fine.

I guess if I put them into concrete piers it would hold. But I am considering a fairly large compressor in the 900# range.

 

[Firebrick43]

Frost heave that you generator is experiencing is going to be in the top 20-24 inches in Connecticut most years. Dig down that far and fill the hole up with clean crushed stone tamping it as you go in layers. The stoned doesn't hold water like soil will and therefore freezing/thawing has much less effect on any lift.

A hole that size is only an enthusiastic 1 hour dig with a spade. Maybe 2 with lots of breaks for the

 

[carlaisle]

Put a 12" concrete stepping stone underneath each of your posts and they won't sink. You can get full composite posts, but they're pricey and not designed for structural use. I would be tempted to use something like this https://www.homedepot.com/p/4-in-x-...ditional-Fence-Post-Jacket-73003561/202084750 and just use it like a form and fill it with concrete. Build your slab on top. You could use standard concrete form tubes, too, but that's a lot more concrete to mix and major overkill for your application.