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Homeowner Forum / Construction / February 2005foundation
Hello, I'm planning on building a house this summer and I started looking at foundation. I'm currently getting the 2 types (regular and foam blocks). What would be the big difference if I was to do a regular foundation with form and add 2" foam on the outside (like cladmate for example)?? I know I cant just slap on the sheetrock on the inside walls and that I will have to build some walls... but what else? how would the insulation compare? Thanks Christian > Hello, > [quoted text clipped - 9 lines] > > Christian All depends on where you're located... Atlantic provinces in Canada, weather is -30 to +30 deg celcuis. Christian >> Hello, >> [quoted text clipped - 12 lines] > > All depends on where you're located... > Atlantic provinces in Canada, weather is -30 to +30 deg celcuis. > > Christian The Canadian Housing Authority (I think that's it) has got lots of great information about building science & technology. I'd do some research on line for their stuff. It'll be better than anything you could get in this NG. The other great site is http://www.buildingscience.com. Check out the "Technical Resources" and "Homeowner Resources." > Hello, > [quoted text clipped - 9 lines] > > Christian Well, let's see...around here a "regular foundation" is a concrete slab either post tensioned or steel reinforced or both. If you added a couple of inches of insulation around the exterior, you would have a floor with 2" of insulation on it, so you would definitely need to build some walls. Maybe you need to be more specific.  SignatureRobert Allison Rimshot, Inc. Georgetown, TX > Well, let's see...around here a "regular foundation" is a concrete > slab either post tensioned or steel reinforced or both. If you added a [quoted text clipped - 3 lines] > > Maybe you need to be more specific. ok it would be a 12" footing and a 8'x8" wall all arround and the foam would be added on the outside of the wall ans under the floor. Christian > > Well, let's see...around here a "regular foundation" is a concrete > > slab either post tensioned or steel reinforced or both. If you added a [quoted text clipped - 6 lines] > ok it would be a 12" footing and a 8'x8" wall all arround and the foam would > be added on the outside of the wall ans under the floor. As a wild guess I think you need to get the footing deeper than 12" ...the bottom of that has to be below the frost line. Unless that 8' wall is below grade, then the 12" footing would be fine as you describe it if thats what a civil engineer, or the city has defined as OK for the soil conditions.. the 2" foam on the perimeter is thin imho. You should imho have a crushed rock drainage below to the bottom of the footer though...you cant depend on any kind of water barrier or the wall not cracking.. you install the water barrier but you count on only for a water shed to the crushed rock drain below it on the perimeter of the slab. and you dont count on the wall not to crack and leak in time..so you need the drain. at 30 below zero I think you might want to look at 4" of urethane for the first 3' below grade at least... then you could go to 2" 2" at grade is going to let your basement wall get below the dew point or even freeze. Im no expert on putting foam under the floor as well... my guess is that you will not need it and it may screw up the slab if you do...since you have the perimeter insulated, there should be no need for foam under the floor at all.. if you want better insulation for heat loss though the floor simply insulate the 8' below grade wall better. Btw I dont understand the 8' wall if there is going to be no basement. If there is a basement you wouldnt be having a slab floor, you would have joists supporting a wood floor in most cases..THEN you would insulate the wood floor. with a slab and the perimeter insulated the ground under the floor will stay at room temperature since the only way it can loose heat is through the perimeter... (straight down you have the heat from the core of the earth keeping ground temps typically at 68 F or so... (with no heat loss from the perimeter).... in your climate though with only 2" foam on the perimeter you will have heat loss from the earth below the slab. thats why I am recommending 4" urethane at least ( 4" styrofoam might work but its dicy) Urethane has approx twice the R factor. It has to be *closed cell though, and rated for underground use. Phil Scott > Christian > Btw I dont understand the 8' wall if there is going to be no > basement. If there is a basement you wouldnt be having a [quoted text clipped - 12 lines] > the R factor. It has to be *closed cell though, and rated for > underground use. Yes ther will be a finished basement at some point, most basement foundation around here dont have any foan at all on the outside, they are simply insulated with a R20 bat. This is why I started looking at the new foam block. these have 3" on both side. Christian Look around & see if you can find a newer beef processing plant that cuts-wraps-freezes-ships beef. (one example) The design is/can be a 3 temperature building. 1 section being cold (above 32), the 2nd section being a freezer (below32) & the 3rd section being a blast freezer (below -25). These buildings utilize a design in the slabs & walls, with respect to foam insulation, that you could model after. You'd need to confer w/ the designer of the bldg. They obviously go beyond your needs but the principal design is there for your review. IF memory serves me right, the slabs were taken down to a certain grade, then they placed around 8 inches of compacted 3/8's minus gravel, then placed a +/-6mil vapor barrier, then placed 8 inches of that pink rigid foam in 4'x8' sheets(2 layers of 4" thick), then placed 6" of sand (to lay the cooling tubes into the refrigerated slab), then placed #4 rebar on 12" centers and poured a 6" concrete slab. Obviously more than you would require, but design wise, it's something you could model after. The walls on this building were 8" thick foam SIP metal panels. 22ga face-then 8" foam-then 22ga interior skin. Dan > Hello, > [quoted text clipped - 9 lines] > > Christian > Look around & see if you can find a newer beef processing plant that > cuts-wraps-freezes-ships beef. (one example) The design is/can be a 3 [quoted text clipped - 16 lines] > > Dan They typically dont insulate the slab floors on the above 32 degree areas, since mother earth is a great insulator once its cooled. below 32 there is sometimes insulation in the slab, 2" of urethane or so in a grid pattern so there are ribs of concrete to support the slab...closed cell insulation so it doesnt absorb water. Below freezing you can build a pyramid of ice with the wide base at floor level and the point going down 10' or more..that will buckle the floor if its not only insulated but the area under the insulation heated to prevent the earth from freezing. The earth will freeze even with 12" of urethane foam since water freezes at 32 and the mean temp difference between inside the box and the farthest point of ice formation, 15' down maybe is exactly half of the delta T. insulation just slows heat transfer it doesnt prevent it. Whats done in those cases depending on soil conditons (clays expand with water 40% or so) depends... Ive ventilated under some of the tougher cases... hot water heating has been used under some. others use nothing and they buckle up in the center.. but the client lives with it..if its a narrow box thats not much buckling. or you can make the slab a lot stronger so the slab stays in tact...and hope the ice pyramid doesnt shove the entire building up, wich it can but usually doesnt. depends on a lot of things. for this basement Id forget insulating the slab entirely since its so far below grade it will run at about 68 degrees regardless the outside weather conditions at 8' (there are regional charts that show prevailing ground temp. in various regions at different depth...go deep enough and you can boil water for instance) Phil Scott mech engr. > > Hello, > > [quoted text clipped - 10 lines] > > > > Christian |
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