Planning to build a 3-season cabin in northern WI (sandy soil, 100' from a
lake, weather extremes but no earthquakes). To spread the costs I'll get
by with a sand point well and a privy at first, add indoor plumbing a few
One option is to contract with a company that builds garages and cabins.
They frame the walls in their factory, erect on a reinforced concrete slab
over 12" sand buildup. They've been doing these for 20 years
Here come the questions. When it comes time for water and septic, I can
think of 3 options:
1) Break up the floor and somehow run plumbing underneath. Is this the
usual practice? Is this even practical?
The other options would mean putting up a small addition (I may be able do
this myself) to hold the pressure tank, water heater and bathroom, route
supply and drain lines through the wall for the kitchen sink.
2) Build this on another slab. Do I need to tie the 2 slabs together and
how is it done?
3) Build it over a crawl space (to hold the tank and heater). Is it even
possible to tie the 2 structures together -- one on a slab, one with frost
footers -- and how?
And what else am I missing here?
place the sewer line under the slab before its poured..... ....along
with a water line.
everything else can be added later.
cost to add sewer line at time of pour very cheap you must decide just
where it belongs in advance.
incidently its cheaper and easier to go larger now than add a addition
A concrete slab on a foot of sand buildup doesn't sound very good. I hope
that you are planning on a concrete stiffener wall with reinforcement,
around the edge of the slab down into the soil. This will stop little
critters from tunneling under the slab and removing the sand.
Hard to say what they mean. You should check it out. It gets cold up there,
the footing should extend down below the frost depth. A floating foundation
must be strong enough to move as one piece as frost pushes it up. This may
be OK for small buildings but larger ones will have problems with severe
cracking. I would prefer a solid foundation with footings below frost. Set
the plumbing into the concrete at the outset and pour it large enough for
the addition to avoid the problems in bonding the two slabs together. You
may want to add foam insulation and a moisture barrier under the concrete to
help keep the cabin warm and comfortable in cooler weather.
Sounds about right, as long as that foot-wide by 10" thick footer beam
(with suitable rebar) is down below the frostline, in undisturbed soil.
Don't forget suitable rebar coming up out of it to tie into the poured
or block walls that lead up to your slab.
Nobody else said it so I will- I'd price it out as slab, and as a floor
over an insulated crawlspace, even if you have to have somebody else
build the floor and this company just drops their prefab cabin on it. If
the place is really remote, getting the crew and redi-mix truck up there
a second time to pour the slab may be around the same price as adding a
conventional floor system to the plans. A wood floor will be warmer, and
plumbing is a lot easier to fix if it isn't buried in a slab.
Of course, none of this applies if they were going to do it as a
monolithic pour, which would be pretty rare below frostline. Listen to
the others- you don't want a glorified garage floor under your cabin.
You want a small house. Personally, if I couldn't do a proper
traditional foundation, I'd do piers before I did a slab. (rebarred
concrete poured in sonotube forms lasts a long time, if done properly.)
Piers are the traditional way to do a cabin anyway, and if the ground
moves (like on a slope), you can always just jack things back into level
and redo the piers as needed. Can't do that with a slab. If your heart
is set on a slab, like most of the others said, rough in your plumbing
feeds and cap them on both ends. It'll be easy to tie into them later.
Rather than a privy, look into incinerating toilets. Propane fired, they
reduce everything to a fine ash.
As for the rest, you may want to look at putting the lines in place now to
avoid ripping up the floor later.
When we had our first house built, we had the builders finish one
bath, but leave the other one unfinished (plywood floor, etc.) and
just used it as a storeroom, figuring we'd finish it later ourselves.
I think they put in stubs for water supply but not the DWV. So later
on indeed I painted the walls, tiled the floor, installed the
plumbing, toilet and sink, etc. and voila another bath. So you could
do something similar perhaps. But a cautionary note: I only did all
the work to finish the bath when we were putting the house on the
market! Naturally when it was all done I stood around thinking, why
the heck didn't I do this before? -- H
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