Foundation Question

[Archena]

In most the references/pic here I've seen folks have used a full slab as a founfation. Is it possible to use a footing (i.e. the slab is only slightly wider than the blocks and is contoured to the stand's shape) instead? I've seen that done for houses (on TV - here we don't do basements often) and was thinking it might be more managable (more of a hassle with the forms, granted) and a bit less expensive (even if I contract out the pour I'll do the forms myself so I'd still think it would cost less).

To keep from having a bare earth floor I was thinking of using brick pavers laid and mortared in sand (like a patio).

[wlively]

Considering they use footings for Insulated Concrete Form houses and buildings, I would think it would not be a problem. But depending on soil conditions and load your footing would probably be a minimum of 2ft wide. With 2 footing per side you are already at least 4 ft across, so you would only save 3 ft of concrete. Concrete is way cheaper than pavers and you would use more lumber. Of course, all these figures are estimates and depend on oven size and other variables.

[Archena]

Okay.


Actually, the pavers are really cheap - there's a place I can scavenge them from. Which wouldn't matter if it really has to be that big.



Edit:

Wait - the footings I've seen on houses aren't that wide. Apron looks to be 2 in on either side.

Soil here is usually clay - pretty solid which is why so many pier houses are still standing 100 years later.

[milehighwoody]

Archena,
I have been wondering the same thing. It seems to me that it would work fine. 16" wide by 8" deep is standard and should be more than enough for an oven. If you are mixing the concrete yourself then it would probably be worth it for the labor savings is the way I see it. If the concrete is being delivered then a slab makes more sense.

Woody

[Archena]

Thanks!

I'd like to do as much of the labor as I can (I'm cheap!) but a full slab is probably out of my capability. Footings I might stand a chance of doing myself.

[DrakeRemoray]

Hi Archena,
I did not use block walls, but poured concrete walls into forms and dug 4 sonotubes for foundation support. I have heavy clay soil and a freeze thaw cycle here. All friends involved (including 1 home builder) say this is overengineered, time will tell...

Discussion of this is located here:
http://www.fornobravo.com/forum/f6/m....html#post2598 (From Mailbox to Pompeii in Colorado)

Drake

[Archena]

Coolness!

We don't have much of a freeze/thaw cycle here - three inches of snow will shut down the whole state because it snows so rarely. Block walls are probably more reasonable for me - that and I want to avoid concrete trucks as much as possible. I plan on moving to a rural setting and a septic system will not be optional. Big heavy things are not good for field lines so unless I'm really sure the truck can easily avoid them, wheel barrows rule.

This is exactly what I had in mind for the floor of the stand. Looks really good, too! Great job there!

Thanks much!

[wg_bent]

Seems to me that pouring a slab is serious overkill. Thus I'm asking if I'm way off base here. How about this thought: Excavate the site (to remove the grass) and put a layer of sand down similar to that prior to pavers. Then use cinderblocks with a flat side down to form the "slab". Add cinderblocks on top of that until the desired height is achieved. Place a sheet of durock on top of the cinderblock pile, and pour the vermiculite concrete directly on top of the durock.
If needed the cinder blocks could be mortered together or use the "fill the holes" technique. Once the weight of the oven is there, I'd suspect nothing is going to move at all. At about a buck 50 a cinderblock plus the labor savings, wouldn't this be sufficient?

What am I missing?

[wlively]

I am sure the professional engineers could chime in here, but I would have reservations.

IMHO: Footings are fine. In my case a whole slab was cheaper and easier than footings and pavers ($100 for a dump trailer filled with 1 yard of concrete). I have a paver patio. But you are talking a serious amount of weight. Too much to be resting on individual blocks that are not structurally tied together. Even well done pavers with no weight but humans and furniture sometimes shift a bit. Rough guess 200 bricks (8lbs * 200 = 1600) plus 23 bags of concrete (23*80 = 1840 lbs) plus rebar (30 lbs) plus 3 50 lb mortar (150) plus roof, framing, and walls ( 640 lbs) , which adds up to 4,260 lbs and I know I am missing something.

Durock is fine for the floor of the hearth form, I used it myself. If you mean solid square of cinder blocks with no opening, then that would probably be OK. The insulation concrete is very brittle and crumbly and is OK only in straight compression. You would need at least a ring of conrete around it to hold it together.

[dmun]

Originally Posted by wg_bent

Seems to me that pouring a slab is serious overkill. Thus I'm asking if I'm way off base here. How about this thought: Excavate the site (to remove the grass) and put a layer of sand down similar to that prior to pavers. Then use cinderblocks with a flat side down to form the "slab". Add cinderblocks on top of that until the desired height is achieved. Place a sheet of durock on top of the cinderblock pile, and pour the vermiculite concrete directly on top of the durock.
If needed the cinder blocks could be mortered together or use the "fill the holes" technique. Once the weight of the oven is there, I'd suspect nothing is going to move at all. At about a buck 50 a cinderblock plus the labor savings, wouldn't this be sufficient?

What am I missing?

OK, lets see. You're in New York, so you have a frost heave situation. There's two ways to deal with frost heave, and easy way and a hard way. The hard way is to dig down to below the frost line, which would be (guessing) 36 inches in long island and fourty two inches in buffalo. Then you pour a one foot thick footing six inches bigger in every direction than your structure. This is the way you need to go if your oven is built into a structure, like mine.

There is an easier way if your oven is free standing. You avoid the frost situation by laying down six inches of compacted crushed stone. This drains off standing water, and frost doesn't accumulate in the absence of water. You need to have a well drained area for this to work, and a significant slab to even out small changes in the soil.

So the bad news is that the slab is the easier way. Methods of supporting ovens, without significant masonry structures, depend on significant welded steel structures, not a single sheet of wonderboard, which cracks when you look at it. Ovens are heavy, and rigid, and hot, subject to thermal changes in dimension and cracking. Any time and money spent in preparation is well spent, in my opinion.