Addition over partially submerged shed?

I have been brainstorming ideas for my backyard. My wife (and I) would like to add an addition to the back of the house off the back living room, maybe 19' x 16' or so. I also really need a shed to get my lawn equipment and some other stuff out of the 2-car garage.

We have an empty spot now next to our large deck and I got to thinking. What if I poured a partially submerged foundation there then built the addition on top of it.

The bottom of the 'shed' floor would be about 3' below ground level. The screenshot shows my yard flat but it actually pitches down away from the house toward a creek that is about 100' back, the creek never fills up. So the ramp going down to the shed door would be flatter then shown.

The addition starts even with my existing deck 3' above grade which gives me ~6' of height in the shed below.

I think this will work but how to I ensure the shed/crawlspace/whatever you want to call it stays drained and dry? Water would be able to enter from the shed door in the front, shouldn't be coming in the perimeter if I pour the foundation 10" or so above ground level all around.

Pitch the shed floor toward the door slightly, install a drain or french drain type deal in that edge then do a drain pipe buried down in my yard toward the creek?

Feasible? Am I crazy? let me hear it.

You could build a elevated roof over the top of the walk out part. Put a drain, sump basket and sump pump in the walk out floor. I would put a sump basket and sump pump in the inside of your basement storage area too. Easy and cheap to do in the beginning.

bigguns69 said:

You could build a elevated roof over the top of the walk out part. Put a drain, sump basket and sump pump in the walk out floor. I would put a sump basket and sump pump in the inside of your basement storage area too. Easy and cheap to do in the beginning.

Click to expand...

Yes definitely to the sump pump. It only takes one heavy rain and you wish you had a sump pump setup.

How about a bulkhead?

Dave in Mass said:

How about a bulkhead?

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Not familiar with the term?

I think I'd try something like this to keep the sump pump activity to a minimum. Pump is still necessary but the less it has to do the better. Doors could be made to match the addition's siding and perhaps be a bit steeper than the ones shown below.

https://www.pinterest.com/lasherpa/outdoor-exterior-basement-cellar-bulkhead-door-ide/?lp=true

https://www.google.com/search?q=bulkhead+cellar+doors&client=firefox-b-1&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj3wt7ryYPcAhUJM6wKHSvwBikQ_AUICygC&biw=1920&bih=938

Most of those shown are for stairs, so yours being over a ramp would need to be longer
and probably home made or contractor made, but it should keep out rain water to a large extent.

That is smart, like a bilco door basically is what you all are talking about, I like it.

Thank you guys, this does look much better I think, I guess since I will be storing wheeled stuff down there it will need to be a ramp still and not stairs, maybe a custom stringer with stairs down the middle 18" or so then flats on the outside or something. Would be a custom bulkhead but not too hard to construct I suppose.

I use sketchup online so I can store and access models from any browser, which limits textures and colors, I just mocked up the door.

ChaseDE said:

Thank you guys, this does look much better I think, I guess since I will be storing wheeled stuff down there it will need to be a ramp still and not stairs, maybe a custom stringer with stairs down the middle 18" or so then flats on the outside or something. Would be a custom bulkhead but not too hard to construct I suppose.

I use sketchup online so I can store and access models from any browser, which limits textures and colors, I just mocked up the door.

Click to expand...

That is a bulkhead

ChaseDE said:

We have an empty spot now next to our large deck and I got to thinking. What if I poured a partially submerged foundation there then built the addition on top of it.

The bottom of the 'shed' floor would be about 3' below ground level.
.
.
.
The addition starts even with my existing deck 3' above grade which gives me ~6' of height in the shed below.

Click to expand...

So what you really are building is an addition with a basement that has double walk out doors. Make the floor deeper so that you have at least 7' clearance under the joists. make sure the basement walls are properly waterproofed from the outside. Install drainage tile around the perimeter tied into a floor drain in front of that and then to a sump pit. Back fill with gravel (common practice for better drainage) to within 24' of the grade.