*
Being a do-it-yourselfer, but not a mason, I’m a little nervous about laying block for a frost footing for my 36×24 cabin. I need 40-48″ of depth, so I planned on laying a 8″x16″ solid concrete footing after the excavation and then 5 courses of block on top of that. Framing will be anchor bolted to the top course of block and the interior slab will be poured to just an inch or so below the top of the block. The outside ground level would be just a few inches below the interior slab.
My question is this; since the cabin only needs something solid to sit on and rigid to anchor to, would it be reasonable to lay the 5 courses of block dry and then fill the voids with concrete and a tie-rod? It seems to me this would be faster and less back-breaking for a rookie like me and should do its job well, barring an earthquake.
I’m sure you guys who can lay a block in 30 seconds flawlessly would think this approach is silly, but I forsee many backbreaking hours ahead and if my “quickie” method would provide the same basic frost footing protection, why not?
-RandyR
Replies
*
Randy,instead of laying block, how about drilling some holes for sonotubes and pour concrete.
*
I'm sorry to interrupt guys...but....
What is a frost footing?
Brewskie
*Randy - - You probably can stack and pour your frost wall,as you describe. I would be inclined to not go more than 2 courses high before I started filling cells, and remember for this to work at all, the lay-up needs to be running bond (verticle joints staggered 1/2 block). Also, your horizontal dimensions will get off as you proceed because the nominal size of block includes 3/8" mortar space top and side to space evenly. Be sure to use plenty of verticle rebar and if possible, a continuous one comming out of the footing at the points where your sill plate anchor bolts will be. The concrete should have a compressive strength of 4000 Psi to handle the expansive pressure of frost rapidly soaking into the ground and exerting lots of lateral pressure on your foundation wall. Don't know what your local is, but it may be a good idea to install 2" styrofoam board vertically around the inside face of the wall to help reduce frost wicking through and lifting the perimeter edges of your slab on grade. Might check code requirements in that area also. It could become an issue if you sell the property. Good Luck With IT. - - Paul M.Brewskie - - In cold climate areas, where the ground freezes solid for most of the winter, a solid footing with it's top below the frost zone and a structural wall on top of it (still down in the soil) is required to provide a solid foundation that won't heave or move structures of about 720 sq. ft. or more. In our area it is common for frost to penetrate into the ground about 45".
*Todd,That would be a great idea if I wanted a crawl space and a wood joist floor, but I like the stability of a slab, no place for critters to hide, and I was toying with in-floor heat. All-in-all, a slab seems preferable.Brewskie,Are you serious? Do you live in Mexico or something? :-)
*Paul,Thanks for the encouraging words. I really expected everyone to tell me I was nuts. Your suggestions made a lot of sense.-RandyR
*Randy,HA!Close.....Anaheim, Cal.....Now North Carolina....Just an ex-surfer dude ya know.....Brew
*You might consider using a preserved wood frost wall on a strip footing.
*Randy,have you considered ICFs (Insulated Concrete Forms)? This would easy for one man to install and you would have no concerns over the structual stability. Check out http://www.greenblock.com for more info or email me direct if you want.
*Randy, I think you got a good thing going. I plan on building an entire basement using the dry stack method. I'll be using a product generically called surface bonding cement, there are several different manufacturers of it . This is a fiber reinforced cement product that is troweled on both sides of the dry stacked block about 1/8" thick - alot like plaster. This gives you a wall that is actually stronger and more water proof than a mortared together wall (not that it matters for your application). You'll still have to put vertical rebar in every so often, code here is 4' and you'll still have to grout the cores. Your anchor bolts would then be tied into the rebar. I'll be putting a bond beam around the top of my basement, I don't know if that's really necessary for your application. The manufacturers recommend laying the first course in a bed of mortar or a bed of the surface bonding cement (none between the vertical joints). This is because the top of your footing will not be perfectly flat and you need to get the top of the first course level. If you get out of level as the block is laid (the blocks themselves may be off a bit) you can shim it. They also recommend mortaring the top course only to level off the top of the wall.I've done my homework on this stuff. I first heard about it in a letter written to the editor of FHM about a year ago.Also, my local block supplier does sell a true 8" high unit just for this purpose. I'd be interest to hear if anyone else has used it. Everyone I've talked to who's familiar with the stuff says it's great.
*RandyUp here in the Great White North I built a cottage in 1998 with footings that differ only nominally, 6/24/24 pad at 48 inch depth and then dry stacked blocks, filling with concrete and lots of rebar. Reasons were similar to yours, lack of Italian blood with no mason skills, plus the logistics problems inherent in a site with no electricity surrounded by water. I did 18 of these and there has not been the slightest movement or cracking. The interior has been drywalled and there has been no cracking there either. The top of only one of these is at ground level, the majority because of the site elevation are 4 and 5 blocks above. One problem I have is a septic tank which does indeed move(up to five inches). I have lived with this by installing a rubber coupling to the cottage plumbing and then removing the metal sleeve and clamps at closeup in the fall. PS When we did our winter check last weekend the temperature was minus 22 F.
*Randy Sorry about that - read 1988 rather than 1998. Time flies when you're having fun. Al
*
Being a do-it-yourselfer, but not a mason, I'm a little nervous about laying block for a frost footing for my 36x24 cabin. I need 40-48" of depth, so I planned on laying a 8"x16" solid concrete footing after the excavation and then 5 courses of block on top of that. Framing will be anchor bolted to the top course of block and the interior slab will be poured to just an inch or so below the top of the block. The outside ground level would be just a few inches below the interior slab.
My question is this; since the cabin only needs something solid to sit on and rigid to anchor to, would it be reasonable to lay the 5 courses of block dry and then fill the voids with concrete and a tie-rod? It seems to me this would be faster and less back-breaking for a rookie like me and should do its job well, barring an earthquake.
I'm sure you guys who can lay a block in 30 seconds flawlessly would think this approach is silly, but I forsee many backbreaking hours ahead and if my "quickie" method would provide the same basic frost footing protection, why not?
-RandyR