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Basement options: SIP panels – concrete walls – or abandon for slab on grade?

YukonBuild2020 | Posted in General Questions on

Hello.
My wife and I are planning to build a SIP house near Whitehorse, Yukon (zone 7, 60degN lat.) this summer.  I can provide more details if anyone is interested but the advice I am seeking now are opinions on my foundation options:

1) SIP panel basement foundation (quoted at ~$14000): 24’x40’x8’ tall, 8.25” thick, R33, pressure treated 1/2” ply on outside, untreated 7/16” OSB inside, pressure treated internal studs (to be placed on a concrete footing); this will take around 1 day to assemble.

2) concrete basement 24’x40’x8’ tall: for the concrete only (no forms/insulation/labour/etc.) for an 8’ tall concrete wall comes out to around $5500 (not including concrete footing); ICFs are an option too.

3) slab on grade, make the house bigger to accommodate a mechanical room, not sure on the cost of this, but a 4” concrete pad ~24×40 is around $2200 for concrete only; seems like this might be a challenge to build myself since I have no experience with these.

Here are some considerations:
– the foundation will be backfilled within 1’ of grade.
– it is very difficult to find any contractors, businessses are working flat out during the spring/summer, so I am planning to hire some skilled labourers and complete all of the work myself.  Also, I am doing all of the design/procurement/budgeting/decisions making/etc. myself (the SIP provider supplies engineered stamped drawings for permitting).  
– the house will be on water deliveries and the 8’ basement will allow us to have 3×1000 gallon water storage tanks, along with work space, storage space and mechanical room.
– it was -40 degrees and colder multiple days this winter, Whitehorse is the driest city in Canada with around 10” of rain per year.

Which would you choose?
Any advice/guidance is appreciated.

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Replies

  1. Expert Member
    Rick Evans | | #1

    YukonBuild,

    Tough call...

    Slab on grade usually entails Frost Walls- which I suspect are 6+ feet in your climate. A 4th option might be an Alaskan or Raft slab with ample wing insulation. This not only saves on excavation and frost walls/insulation, but can also save on flooring, subfloor panels, and floor joists (compared to basement). Yes, you will need extra space for mechanicals on main floor, but with a basement, you will need extra space for stairs on the main floor.

    Unless you have some concrete experience, there is no way that I would attempt a slab or pour of any kind on my own. A slab that serves as finished floor in particular seems to be as much art as science.

    In your climate, where there is little moisture and no termites the SIP option actually sounds pretty good. I would really be careful about drainage (lots of washed/crushed stone, filter fabric) just to be safe to keep those buried walls dry. If you store water in basement, I might also include some kind of interior drain in the event that one of your tanks floods the basement. That would destroy the SIP's interior OSB and create some structural issues. An engineer would also certainly be needed to address those repairs.

    1. YukonBuild2020 | | #2

      Hello Rick.
      Great advice, especially regarding the basement sump.
      Indeed, I have no experience with concrete slabs and I just don’t have time to learn techniques so I will most certainly skip this option as well at the raft.
      I agree the dry climate will support wood below grade wood and givin rapid/ease of installation I will be going with the SIP foundation.
      I think I will build a short concrete wall (1’ or so tall) on the concrete footer and place the SIP on this which will provide containment for any potential water tank leaks and further protect the SIPs.
      Thanks again.

  2. Yukonlass | | #3

    Hello, my partner and I are planning a build in Whitehorse this summer (2021). Which company quoted you for your SIP foundation?
    Thanks!
    Shannon and Mike

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