Tool for new Outbuilding foundation dig

[eclipse860]

I just had a 40x36 post building erected. Concrete is not poured yet. I am stubbing in Conduit and other utilities. I would like to dig around the inside of the perimeter to lay 2-3" of foam board for insulation.

The base layer is about 8-12 inches of VERY dense, rocky material. They had compacted it down with a large machine in prep for the concrete. I just dug a hole by hand to stub in conduit for electric. It was back breaking work with a pickaxe and misc. shovels. It took me about an hour to dig a 1 foot wide, 2 foot deep hole from inside to outside. I cannot image digging 18" down around the entire perimeter so I can slot in the foam board.

Does anyone have tools suggestion or methods that might make this easier? I feel that I may need to abandon the idea :-(

 

[GeoBruin]

SDS Max rotary hammer with a clay spade?

 

[signcrafter]

SDS Max rotary hammer with a clay spade?

This

 

[metaldad]

you're going to excavate, next to the base layer just put in?

 

[coldh2o]

SDS Max rotary hammer with a clay spade?

Ugh, I wouldn't want to do 152' of trench with this.

I'd say best option is a mini-ex. Wider excavation, but it will be easier to backfill and compact with a jumping jack or plate tamper.

 

[sparky 1971]

Rent one of these.

 

[jdl25]

Is 3" of foam below the dirt worth all of that? I'd spend time and money elsewhere. But it is your building and you should do it however makes you the happiest.

 

[billconner]

I think Hansen Buildings recommends a ditch witch trencher or similar, but when just posts are set, no walls.

If you're in a cold climate and heating building it makes a lot of sense to me.

 

[GeoBruin]

I think Hansen Buildings recommends a ditch witch trencher or similar, but when just posts are set, no walls.

If you're in a cold climate and heating building it makes a lot of sense to me.

That's a good idea.

 

[mike93lx]

A trencher is my thought too.

Get a tracked unit. Don't settle for a wheeled one

 

[billconner]

But not if walls are up based on what I read. Hit a big rock or pipe or something and you might tear a hole in sideling. No personal experience in this one.

 

[mike93lx]

But not if walls are up based on what I read. Hit a big rock or pipe or something and you might tear a hole in sideling. No personal experience in this one.

With the big ride on, tracked units, I have found they don't jump around. They get stuck and shudder, but they are quite heavy

 

[RPH]

I have an older articulated Vermeer trencher unit. Weighs in at 9000#’s. If you hits something big enough it will jump and buck around. One time it pulled an old stump from two foot down. That was a ride! But it’s one way to trench it.

 

[RTM]

I wouldn't want to use my Bosch demo hammer to dig more than about 5' of trench. If you use a trencher, pay attention to the direction of the exhaust pipe. Buddy stained his stucco with a dark stripe.