Hi Everybody,
I need some help with the foundation and insulation of the ground floor system. I live in Northern Canada. It can really cold up here almost -49 ºF and also really hot in the summer 95 ºF. I plan on using Pier Beam Foundation.
I recently purchased the 20x34 classic 2-story and will more or less build it to spec, except for the foundation. I want to over engineer the foundation in order to ensure that is durable and can withstand earthquakes and hurricanes, and that I never have to worry about it again for as long as live!!! :) Maybe it is too much overkill? Please tell me. The frost line is 5 ft, and 6ft if unheated according to city building codes.
My plan is to use bigfoot concrete forms. The concrete piers will be 6ft below ground and 18 inches above ground. 16 inch sonotubes will be used.
http://www.bigfootsystems.com/include/bf36.htm
I'm going to use 6 or 7 piers along the 34 ft sides and 5 piers in the middle for my girder. (i'm not using engineered floors).
Similar to this:
http://www.countryplans.com/images/gr-piers-1.jpg
I also want to use an 6x8 or 8x8 PT beam. The fellow used a smaller beam like so:
http://www.countryplans.com/images/gr-floor-1.jpg
Questions:
1. What kind of bracing/bracket do I need? If you can provide a link that would be awesome.
- How deep should the bracing be submerged into the concrete?
2. Do I need to fill the concrete piers with rebar and wire mesh for additional support? I assume yes.
3. I assume the PT wood can sit right on the concrete?
In terms of insulation of the floor system. I'm using 2x10 joists and using pink fiberglass at R-30. Underneath the floor system I will glue/nail foamboard. I will also put a sheath of rocks around the house to prevent any critters making a home for themselves in the insulation.
Questions:
1. Can I do any better? Probably :) But what? :)
2. Should I glue/nail some plywood over the foam board to protect it and keep critters out?
3. Should I use PT wood for rim-joists and floor joists and floor plywood sheathing? (even though it is insulated underneath)?
Thanks in advance for all of your help!!!
Regards,
Cono
Hi Cono w* to the forum;
You've hit a topic I'm not shy about.
QuoteI want to over engineer the foundation in order to ensure that is durable and can withstand earthquakes and hurricanes, and that I never have to worry about it again for as long as live!!! Maybe it is too much overkill?
I don't know Canadian codes but you aren't even on the radar in the US with that type of foundation without engineering. Write Bigfoot and ask for code compliant residential foundation design help. I do know what the response will be for here.
Wind and seismic loads are lateral, sideways. Foundation walls resist this type of motion,
(https://i180.photobucket.com/albums/x109/windyhilll/crawlspace.jpg)
piers simply topple.
(https://i180.photobucket.com/albums/x109/windyhilll/unbracedpiers.jpg)
An engineer is qualified and capable of producing a safe pier type foundation. The rest of us are simply guessing and not very well. You don't need to over engineer it but you do need to engineer it if you go this route.
A conventional reinforced continuous footing distributes the loads uniformly to the ground with little pressure, a big snowshoe. Piers individually act on the soil with different loads and far greater pressure. This often results in differential settling of the structure.
Quote from: Cono on June 25, 2012, 06:34:18 PM
I recently purchased the 20x34 classic 2-story and will more or less build it to spec, except for the foundation. I want to over engineer the foundation in order to ensure that is durable and can withstand earthquakes and hurricanes, and that I never have to worry about it again for as long as live!!! :) Maybe it is too much overkill? Please tell me. The frost line is 5 ft, and 6ft if unheated according to city building codes.
w*
I don't know the Canadian equivalent, but down here we have the Federal Emergency Management Agency (FEMA). On their website they have special regulations and designs for areas, such as coastal areas, prone to that type of weather. You can use the search function here and probably find the link.
Almost every pier design for traditional piers has a full continuous footing with continuous rebar columns coming up from those. The only type that doesn't is a driven pile foundation. They go about 30ft into the ground.
My other concern is that in Northern Canada you probably have one of the highest snow load requirements on the planet. With a 2 story house in addition to this, this is a lot more weight than you think it is. There have been many topics on how to calculate load on the forum. Tracing all that weight to the ground and putting it on concentrated points (piers) might exceed soil bearing capacity. I would be willing to bet the current beam/headers design may have to be sized up and probably the rafters.
Did the city approve a pier foundation? It is not prescriptive in most codes.
The snow load may not be as heavy as you would think in many parts of Northern Canada. Snowfall is high on the west coast, and much less in the western interior and central areas. Some places are even an 'Arctic Desert' with very little snow accumulation. Maritimes see heavy snow loads I think.
It's interesting to see old Canadian cabins built 50-100 years ago without proper foundation in areas of permafrost. Most are serioulsy atilt due to melting of the substrate. Foundation construction techniques in places like Inuvik are unique to say the least.
Maybe it would be worth some local professional engineering advice for a proper foundation for conditions in your area?
Hey Guys,
Thanks for your responses. A basement in my area with walls below the frost line is about $16,000. Because of building codes, footings need to be 8"x20" and 6ft deep. They also have to backfill with sand. If I just build a crawlspace it won't be much cheaper than a full basement because of the depth. I can't afford that. I spoke to an engineer and the cost to draw it up would be $1500 to $2000.
Regards,
Cono
my cabin is on wooden log posts from the 60s with nothing under it but ground!!
im thinking about jacking it up and at least putting a concrete block under it.
I built a full crawlspace out of block with a 5 ft depth on a 20x30. Cost about $3100. Fully code compliant. The only thing stronger would have been a solid concrete pour.
Weekend Mini-excavator rental $600 delivered. Really easy to learn. Took about 10 minutes. If you grew up with video games it is just two joysticks.
Footing Forms and rebar $150.
3 yards of concrete delivered $300.
Concrete block and Mortar delivered $1500.
Sill plates and J bolts $150.
Center beam $150
Weekend rental of walk behind loader to backfill inside and out $250.
Although it is a single story, I built it able to handle a two story load in case I wanted extra space later.
http://countryplans.com/smf/index.php?topic=10998.msg140857#msg140857
If your code requires a minimum 8x20 continuous footing, I can't imagine they would allow a pier foundation. On a wood framed house, that size footing is larger than required for a 2 story house on the worst soils. The only reason I could deduce for that is extreme snow load.
http://publicecodes.citation.com/icod/irc/2012/icod_irc_2012_4_sec003.htm
Stronger and probably costs a few thousand less than the piers if you need the engineer.
Cono:
The stated requirements for your footings are pretty unusual. Eastern Canada can have some pretty nasty soils. Ice lensing (http://en.wikipedia.org/wiki/Ice_lens) may be one of the things you have to deal with (it can tear concrete basement walls apart if they aren't surrounded with a drainage plane and exterior foam insulation).
I think if you want what you say - "I want to over engineer the foundation in order to ensure that is durable and can withstand earthquakes and hurricanes, and that I never have to worry about it again for as long as live!!!" Then you are probably going to have to invest in a basement foundation or deep crawlspace. A pier foundation is not likely to work unless you did deep piers tied into a concrete grade beam. I suppose you might be able to do that with Big Foot piers but that would likely have to be engineered as well. I think your best bet is to talk to local foundation contractors who work with the local building department and then use some thing that has been well proven to last and can be easily permitted in you area.
(https://i1009.photobucket.com/albums/af219/countryplans/super_foundation.jpg)
In case someone wants to know what it takes to build a well insulated long lasting basement foundation that can withstand the worst Canada can throw at it.
I will place my comments in blue.
Hi Everybody,
I need some help with the foundation and insulation of the ground floor system. I live in Northern Canada. It can really cold up here almost -49 ºF and also really hot in the summer 95 ºF. I plan on using Pier Beam Foundation.
I recently purchased the 20x34 classic 2-story and will more or less build it to spec, except for the foundation. I want to over engineer the foundation in order to ensure that is durable and can withstand earthquakes and hurricanes, and that I never have to worry about it again for as long as live!!! :) Maybe it is too much overkill? Please tell me. The frost line is 5 ft, and 6ft if unheated according to city building codes.
My plan is to use bigfoot concrete forms. The concrete piers will be 6ft below ground and 18 inches above ground. 16 inch sonotubes will be used.
http://www.bigfootsystems.com/include/bf36.htm
These require almost as much concrete for the footings as a full foundation. At 36" wide you will probably need some heavy equipment anyway to install them. Why not just go with the full foundation?
I'm going to use 6 or 7 piers along the 34 ft sides and 5 piers in the middle for my girder. (i'm not using engineered floors).
Similar to this:
http://www.countryplans.com/images/gr-piers-1.jpg
I also want to use an 6x8 or 8x8 PT beam. The fellow used a smaller beam like so:
http://www.countryplans.com/images/gr-floor-1.jpg
Piers and girder sizing and spacing are dependent upon each other and ground snow load. You can view the charts here.
http://publicecodes.citation.com/icod/irc/2012/icod_irc_2012_5_sec002_par015.htm
If you have difficulty reading the chart, I wrote a walkthrough here:
http://countryplans.com/smf/index.php?topic=10511.0
I believe your plans should have the sizing in them. If you have a ground snow load of 70 p.s.f. or greater, which is high in the U.S but can be higher in regions near the Canadian border, then an 8x8 would be slightly under recommendations if you had 6 piers. As you can see in the chart spans, taller is better than wider (think I-beam).
Questions:
1. What kind of bracing/bracket do I need? If you can provide a link that would be awesome.
- How deep should the bracing be submerged into the concrete?
2. Do I need to fill the concrete piers with rebar and wire mesh for additional support? I assume yes.
Yes. Rebar.
3. I assume the PT wood can sit right on the concrete?
Yes.
In terms of insulation of the floor system. I'm using 2x10 joists and using pink fiberglass at R-30. Underneath the floor system I will glue/nail foamboard. I will also put a sheath of rocks around the house to prevent any critters making a home for themselves in the insulation.
Questions:
1. Can I do any better? Probably :) But what? :)
A full length foundation wall. There are half of a dozen different kinds prescriptive in most codes. You can backfill both sides if you want and not have to worry about the lateral force of the soil on the walls.
2. Should I glue/nail some plywood over the foam board to protect it and keep critters out?
Galvanized hardware cloth would be better.
3. Should I use PT wood for rim-joists and floor joists and floor plywood sheathing? (even though it is insulated underneath)?
PT wood is only usually required for wood in contact with concrete, the ground, or within 18" of the ground. I generally try to avoid using it as much as possible. It tends to warp, bend, twist, cup, and shrink so severely it can ruin my day. I would prefer one of the new weather exposure panels if I was going to take a while to get it dried in. They are both cheaper and will give you less problems than PT plywood.
Thanks in advance for all of your help!!!
Anytime. We love this stuff.
Regards,
Cono
Hey All:
Thanks for your responses!! I decided to bite the bullet and go for a full basement. It will be 5' 1/4" walls sitting on 8"x20" footings. I will add 4'-6" knee walls.
Cheers,
Cono