I'm putting together my gameplan for building (actually rebuilding) a small
shed for the yard. It's going to be a 10' x 16' saltbox. I have a couple of
questions I was hoping someone could help me with. First, on of the 16'
walls will be partially below grade (the shed is going to be built into a
small slope) so I plan to use pressure treated sheathing on that part, as
well as applying an additional wood preservative (cuprinol or other
product?). Should I also apply another barrier such as plastic sheeting or
typar? And would I gain anything by also using pressure treated studs to
build the walls that are below grade? My initial thought was to build a 3 or
4' knee wall on the offending side and then build another wall section from
regular studs to attach to the top. The question that arrises with method
two, how do I frame the windows in. Assuming there would be a double
sill/header where the knee wall meets the upper wall section would I need
additional jack studs in the knee wall, under the window edges?
Second area of concern is the "foundation". The floor of the shed will be
crushed stone. I plan to dig a trench under footprint and put in 8" to 10"
of crushed stone with drain pipe just inside the walls, then lay 6x6 PT
timbers surrounded by crushed stone with the tops at grade of the finished
floor and then build on top of those (PT sill plates would be nailed to the
6x6 posts. Does this seem like a horrible idea? The current construction
(not my project) utilized 4x4 posts installed at the corners of the shed.
They were put in at least 2' into the ground (I haven't dug any further to
see just how deep they were) and they continued up the the top of the wall
of the shed (existing shed is gambrel style so the wall is only 4' above
ground before the roof angle). Does this seem like a better idea or even an
acceptable method? to be honest, despite all the problems with the current
shed, It does seem that the 4 corners are still square.
Thanks in advance for any help and advice.
All things being equal, seems the 2 side walls will also have some below
grade as well.
Some obvious landscaping, on the side where the high slope is, may prevent
or reduce eventual soil and plant debris buildup. Ideally, will cause
runoff to go around the shed.
Insects and other small varmints can be concern on such a floor you've
I wouldn't put any part of a wood framed or wood sided structure
below grade. Choices could include a retaining wall to keep the
high ground back away from the structure a few feet with plenty of
drainage under or around the structure or creating a concrete or
masonry stem wall.
Keep the whole world singing . . . .
If you're going to do it, why not do it right? Pour a footer below
frost line, lay a block wall to above grade and build on that w/
conventional framing and floor joists. Or a variety of the same or
level the area...
What you're talking of doing is simply silly to waste the effort and $$
unless you're 70+ and don't care that it will fail (which it will...)
Maybe I overlooked something. I saw no indication of location that would
indicate a frostline need regarding footers.
Irregardless, he could put the entire shed with a wooden floor on pier and
beam above ground level. Alleviating all the potential factors of soil
intrusion, insects, varmints, and ground freezing degradation.
" = inches
' = FEET
Why not work the land on the up-hill sides of the building?
2 1/2 inches shouldn't take a lot of work.
I would consider a curtain drain / french drain on three sides with
Pressure treated wood will still rot, it just takes longer.
If you want the shed to sit right in the slope of the land, you should
install a proper concrete (block or poured) foundation on the back and two
sides at least 6" taller than the high point of the slope. Then frame your
wood walls on top of the concrete walls. Be sure to apply a waterproofer to
the outside of the concrete and install a french drain before backfilling.
Another alternative, cut the hill back another two feet or so and install a
retaining wall behind the shed. This will keep the soil away from the wood
structure, and prevent rotting. You can find retaining wall blocks at any
home center to do this quickly and easily, but there are many other options
for retaining walls also.
By the time you pay for 6x6 PT timbers and all that crushed stone, you
could have just layed a plastic sheet for a moisture barrier and poured a
concrete slab. MUCH more durable, fewer moisture problems, easier to clean,
and it will keep out bugs and other critters.
Building a wood structure in contact with the soil is just asking for
trouble. Build a proper concrete foundation, cut the hill back so it's away
from the building, or raise the building up above the soil.
There are two methods...
1) No back fill - Since it's only 2 foot you can dig out an area larger than
you need and either slope the sides or build a retaining wall. Build the
shed in timber with no special treatment.
2) Backfill - Then you must build in block and tank the uphill side below
ground or you will have a shed full of water. Doing this in timber would be
Thanks to all for the responses. The general consensus seems to be that PT
is not a great idea but may be feasable. I think I'll aire on the side of
caution and build a small retaining wall just outside the footprint, and
build a full shed wall. We are in "snow country" so frost and heaving is a
potential issue, however, for a small shed such as this, digging and pouring
a frost wall is not going to happen and seldom does in these parts.
So beyond that, the floor to the shed will be dirt (crushed stone actually)
and this is a functional decision not me being cheap so no snide comments
please. What would be the best way to construct a sill for the shed. I was
thinking of laying 6x6 timbers in crushed rock with appropriate drainage and
then attaching the sills & walls to this. Perhaps a better method would
involve cement pads at the corners? or something else?
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