To All:
I have had great luck with responses so far, so I am back at the FHB “well†again.
We are building a new house (although most of the “building†has been done on paper so far).
As you may recall from previous posts, we are building in No. MN (cold!). Our house site has been excavated to ledge rock. The depth from grade to ledge rock varies between 12†to 22â€, and we don’t want to gain too much height, or the house will “loom†over the site. I have been doing some preliminary courting of builders, and they all have a different approach to what I should do for the first floor & foundation.
We want hydronic radiant floor heat.
Here are the options I have been given:
1. Shallow frost protected slab with Wirsbo PEX tubing. They would truck in “good†dirt (gravel/sand) to form the compacted base (which would be placed on the excavated ledge rock), and the slab would be formed up with 2†foam around and under, vapor barrier & PEX placed, and floor poured.
2. 8†deep footers pinned and poured to ledge, with 3-4 courses of block laid on top, this “hole†would then be filled with a compacted base, 2†foam under slab, and an 8†strip of 2†foam glued to the top course of block, and then a slab with the PEX would be poured level with the top course of block.
3. Footers and block combination as above, but conventionally frame the floor, and use a RFH system such as “Warm Boardâ€. Insulate between joists. Insulate block walls. Place a couple of electric baseboard heaters to keep crawl space just above freezing. Place vapor barrier over ledge.
4. Footers and block combination as above, conventionally frame the floor, install 2†“sleepers†and install PEX and put a “special†concrete pour between the sleepers (not gypcrete). Do not insulate between the floor joists, but insulate the walls of the crawl space with 2†foam. Maybe pour a “rat slab†over the ledge rock to make it easier/cleaner to move about the crawl space.
5. Blast and make a basement.
The SFPS guy tells me this will be the cheapest option, and I will not have any settling / moving problems.
The footer/block wall/slab guy says this is the “right†way to do a slab floor (I will never have any settling / moving problems).
The crawl space guys tell me that someday you will want a crawl space to repair / change your mechanicals. Yea, you have to heat a space you will never use and can barely “crawl†in, but such is life.
Now I am looking for opinions. Of course we want the best value, a mix of cost effectiveness, ease of construction, and effectiveness of the RFH. We plan on being in the house for years, so this is not a “build and move on” deal.
Help me land on an option that I can explore further with one of the builders…..This is hard stuff…..
Oh, the house footprint is a simple rectangle.
As always – thanks!
Pinemarten
Replies
I am not at all familiar with building on ledge. I will say that I like the heat I have gotten out of our RFH in a slab with ceramic on top. Placed to pick up the suns passive heat and mass that has been economical to operate for the last 12 winters. I wouldn't put wood over it, I wouldn't put carpet over it. You can spill your redwine anywhere and dump the mop bucket cleaning it up. The slab should be isolated properly from the foundation wall and from the fill below. Downside? No quick heat, a good masonry heater solves this, uses little wood and retains heat a long time. We will eventually be burning a log bag of wood to keep the home comfortable each evening. Not much more will be necessary as the shading trees lose their leaves. Last year, though a mild winter, we didn't turn on our main floors until December. If you plan on it as your only source of heat, no back up, then remember the start up costs associated with hose in a slab. Evening chill, floor goes on, but takes a couple hours of "boiling" to warm up. Stays at temp all nite, then on the sunny fall/spring day the sun comes out and your house receives all that passive energy, floor shuts off and cools down. That nite the cycle repeats. This is alot of reheating of a slab. Now, if you're up above Chisholm, hell it gets cold early and doesn't really warm up till spring, if then. I still recommend some alternate or back up quick recovery system if you can. Now to the building on that tough base, Best of luck.
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Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
latter choices would be problematic.
#1 or 2 is right. I lean toward #2 as best with #1 aas acceptable.
Primary deciding factors would be budget and weight of structure. A large house would more likely require the foundation to ledge. The Slab on grade would be less expensive but it is absolutely essential the the fill be compacted well in lifts and that adequate steel be used.
Excellence is its own reward!
I live in MN too, not much experience with building in the NE part of the state though. I would go with #2. I like the fact that it has a solid attachment to the ledge, (think BWCAW blowdown). I think the thermal mass you get with the slab makes more sense there too. Gives you more "cush" time in a power outage. How are you going to fuel your boiler? Make sure the tubing is tested before you pour, and use glycol, or similar in your boiler to frost protect. It's too expensive not to.
Steve
I'm no foundation expert, so maybe this is as moch of a question as a suggestion.
Assuming you go with option 2 - Would it be better to go with ICFs than setting concrete blocks and then trying to insulate them?
To the welfare state another person means another mouth; to the capitalist economy it means another mind. [William McGurn]
For what it is worth - after seeing all the problems my mother had digging up her concrete floor in CA to repair leaks when the "earth shiffted", I swore that I would never embed piping in a slab. I have a similar site in NH. I have choosen to blast 4 feet into the ledge and build with an ICF basement and potentially use radiant floor heat via geothermal. In that manner I have access to all the utilities.
Ron