Canadian house on piers
jarf
| Posted in Mechanicals on
Planning on constructing a house on piers over bedrock- is it feasible/practical/permitable to run water supply & drain under the exposed floor, bundled in an insulated conduit of sorts? I’’m picturing the pipes wrapped in heat tape etc, then spray-foamed and boxed in with wood…. any thoughts on this approach would be appreciated. Also great thanks to Martin, Joe et all for their generosity and unbiased discussions- what a great space and resource you guys have here.
-Jeff from Muskoka
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Replies
City water and sewer or are you getting it from a well and running a septic field?
thanks for reply- should have mentioned this is a rural build with well and septic
Jarf,
Are you going to do some blasting?
Where is the septic field? How far does this bedrock extend?
How far away from your house is the drilled well?
You're going to need some trenches. Sounds like a job for explosives.
Once you get your trenches established, you can bring your water pipes and drain pipes up to your bathroom or mechanical room through a small, very well insulated airtight room that extends from the bedrock to your subfloor. That room will require heat tape. The "room" can be as small as 12 inches by 12 inches.
Hi Martin! The site we have chosen is at the foot of an exposed bedrock slope which emerges out of a sandy flat zone, in which we plan to locate septic&wellhead. proposed main living space would sit about 10’ above sandy plain... our rough sketchup plan shows the essential idea:
Also, I should have stated that the specific idea I’m on is to run the pipes along the bottom of the floor to service different areas of the house, in order to simplify the plumbing.. Is it worth the energy cost of heating the external supply lines? Thanks.
Jeff,
As Martin alludes to, the bigger problem may be getting the services to the house, not up into it. Once you are under the house, I've had good luck with a variant of Martin's "room". I build an insulated "core" about 3 feet square, open at the top to the house above. It relies on heat from the house to stay warm, as opposed to another source which might fail.
Thanks Malcom, some such system seems economical compared to icf etc.
If you have a well, you may be using this "room" to hold your pump in addition to being the transition point between above-ground and below-ground piping. Given that, you may consider making it physically separate from the house (no shared physical wood that can carry vibrations and definitely no shared air) to isolate the pump noise and that would call for it to be heated independently.
interesting! and goes along with the general aversion to mechanical noise pollution.... was thinking about these issues while staying in the inlaws basement over the holidays and listening to the drains in the walls haha
Part of your question which seems unanswered is what to do with the plumbing under the floor (not just at the gap between the floor and the ground.) Presumably you will want to insulate the floor very well. Supply lines seem easy - you could run them close to the bottom of the floor (the top/warm side of the insulated floor cavity. It would also be reasonable enough to run those through your walls.
Your drain pipes might be more challenging. You are going to need to maintain a slope and that may introduce some challenges. If you have a toilet at one end of the house , that drain pipe may need to be touching the bottom of your floor cavity (the cold side) by the time it reaches the area where you exit the drain pipe out of the house so how are you going to stop that pipe from freezing up in a cold Ontario winter? Have you run the numbers to see how much drop you will have from your furthest drain to the edge of the the house where the drain will exit?
Thanks again. I guess the question becomes: is heat tape on external drain an unwise or uneconomical proposal. plumbing is not consoldidated in our plan which has bedrooms at opposite ends, but we do have elevation under the main floor to merge drains at grade...
I'm not sure I follow.
You will have an insulated cavity below the floor right? Are you convinced that the drain can not fit inside that cavity?
thats the idea- an insulated cavity hung from the bottom of the floor to accomodate drain and/or supply, running to mechanical room, where everything goes underground. seems plausible unless OBC somehow conflicts. trouble with external wellhead/pumpspace is water still needs to be heated
Why not bring all the underground pipes from the well and going to the septic up through a slab on grade and into a heated mechanical room attached to the side of the house (looking like a lean-to shed)? Then you can route the pipes into the house through the connecting wall and underneath an interior false floor to the bathroom and kitchen. That way the pipes are never exposed to outside air and freezing temperatures.
thanks, i dont think i could fit the drains in a false floor given the long runs required. also would add cost + construction time significantly, no?
Well.. at 1/4" per foot, you are looking at around only 1 foot for a run of 48 feet.
How much distance do you anticipate having between the tiles in your bathroom to the bottom of your floor joists? In other words, how large of an insulated cavity do you anticipate having beneath the surface you are going to walk on.
You may actually have a larger problem with the rapid drop at the local it leaves the house to get to the ground. That type of a drop may serve to evacuate the pipe of liquids and leave the solids behind. Have you talked to a septic company yet?
Ive been planning on 2*10 joists spanning girders spaced at 10’. but even with 2*12, i don’t see enough depth to facilitate the drains merging, elbows, etc. cutting into the floor structure so extensively could likely be problematic or prohibited, no? thanks
Jeff,
Consider using parallel-chord trusses as your floor system. You will get longer spans, need less piers & beams, and they will provide a deep enough cavity you can keep the drains warm without additional heat.
A lot of the older houses around here have pipes susceptible to the infrequent freezing we get in the PNW, and rely on a mixture of insulation and heat tape. It works, but is a very second-best alternative to having them within the conditioned enclosure of the house.
malcom, i’ll have to do some significant number crunching to process this intriguing suggestion.... i lived for years in a cabin on footings at grade, in the northern rockies. the waterline popped out of the ground and entered the bathroom wall. it was enclosed in a crude shed stuffed with pink batts, and wrapped in heat tape. it never froze on me unless the power went out, through many -40 coldsnaps. so while not an elegant solution architecturally speaking, i’m still attracted to the simplicity, quiet, floodsafety(in the event of a burst line), and economy of the “conduit” approach. Though have yet to calculate long-term energy usage of an admittedly great length of heat tape. Thanks so much.
Jeff,
In some ways the best solution is the one you are most familiar and comfortable with. If you do make a "conduit" think about how to build it so you can access the pipes if necessary. One of my clients insulated their pipes on bedrock and then encased them in a concrete sleeve. You can imagine what happened next.
yikes, thanks for your advice, it’s given me cause for consideration for sure.
Well, it depends on the depth of the false floor and where on the main building you attach the mechanical shed. If you place it in the middle of a long wall (probably the north wall) you'll have much shorter runs than if it is at one end of the house and the bathrooms are at the other. Otherwise your option is to run the drains in the main floor system which increases the risk of the pipes freezing.