Brainstorms needed - Extending a shed addition on a slope.

[timb]

In the teach an old barn some new tricks category-

I've got a 16x24 outbuilding in "bank barn" style with a cement block wall foundation/lower level. The grade slopes two ways - left-to-right and front-to-rear. The grade comes to within 3 courses of the top of block at the left front but nearly 10 courses are exposed at the right rear. Have absolutely no idea how far below grade (expecially at the right rear) the wall goes or what kind of footer might be down there but the foundation seems solid enough and there's been no settling or shifting in at least the last 15-20 years or so.

On one end of this structure is attached a "3 sided" pole shed addition. One big post set at each of the front and rear outside corners with the roof tied into the rest of the barn. The floor (dirt/gravel) runs in at grade in the front, and "was" built up level inside. This addition is about 10x16 feet. This section needs some work (actually the whole barn does, but one bit at a time!) - and while I'm at it I'd like to extend it to the rear another 4 feet or so. However the grade slopes down that direction now - and the back end of the "floor" is already sliding out. (Aided by groundhogs).

I suppose the most solid, permanent solution would be to do it right and dig down below frost line, pour a perimeter footer attached to the existing foundation, and build back up with block. However this shed is supposed to be temporary storage. I've got plans to build a new, much larger barn elsewhere on the property maybe 5 years out so I'd like to keep this project low key.

I've got no problem sinking a pair of 6-by posts back there to mark new rear corners - but how do I build up a "retaining wall". I'm just not coming up with anything creative on this one.

The attached photo shows the barn from the front - the shed addition is on the left.

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Rear view (the low side) showing the back end of the shed addition (to the right).

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Front 3/4 view showing the shed addition end.

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And yeah, I know there's a lot of issues with this building (love the blocks holding down the roof metal!) [img]/forums/images/icons/tongue.gif[/img] but really it's more solid than it looks (would have to be to still be standing).

[Autotech]

2 methods come quickly to mind:

First would be to use one of the ready made retaining wall systems you can get from places like Home Depot. These prefab blocks work great because they interlock, and you don't need a really intesive foundation. Using gravel to backfill the area immediately behind the wall will allow it to drain and help prevent frost heave.

Second, and probably cheaper if you look hard enough, would be to sink I-beams at your corners, and then slide 6X6 or 8X8 pressure treated timbers into the I-beam channels. If you shop carefully you can come up with used I-beam reasonably cheap, and railroad ties work great, if you get them at the right price. I'd lean the I-beams in at the top just a bit to give you a head start against the wall bulging out, and again back fill behind the wall with gravel. And be sure to drill weep holes in the bottom tie for drainage, or space the ties apart about an in with shims.

Gregg

[timb]

Gregg - are you thinking of a "retaining wall" under the edges of the actual shed - or as a "perimeter" somewhat outside the corners (and corner poles) of the shed.

I've been trying to think of an efficient way to simply sink long poles (posslbly a pair of 16' 6x6) at the "new" rear corners. Down 4' below current grade - then build some type of retaining crib that uses those poles. I could then "fill up" the volumn inside to level the floor. (Not planning a cement slab-compacted soil with gravel/fines surface is just fine-it's dirt now.) However - every configuration I can think of like that has one issue or another.

Sinking the long 6-bys at the corners as described and then building up an independent retaining crib work outside of that seems to be the only way that might work. The only problem I have there is figuring out 1) how far outside of the poles I should go with the cribbing and 2) how much I want to narrow the gap between this building and a second outbuilding behind it. Right now there's about a 15' gap - with a pole gate between them. I'd like to retain enough room to easily drive a tractor through that slot, but a 4' building extension and 2' or 3' of retaining "terrace" starts to tighten that up a bit.

Tim

[Autotech]

If you substituted appropriately sized I-beam for your 6x6 corner timbers, and oriented them so the open channels faced each other, you could simply stack 6x6 or 8x8 (or whatever size) timbers in the pockets to the required height. Where you have a corner some angle of the correct size could be welded on the plain side of the I-beam to provide the required pocket. Also it may be possible to have I-beam driven into the soil saving the time and effort of excavating to install posts.

Gregg