Leveling the stand, hearth etc

[mrpbjnance]

I just poured and checked my slab and to no surprise it is not perfectly level.
Its not to bad, but not level.
Now, if I take the time to level out the first course of my bricks for my stand what will guarantee that when I pour the hearth it will be level? Can I just take the time and do whatever is required to level my hearth before I put the super isol on, or should I really take the time to level the stand and level again when I do the hearth?

[james]

My view is that the hearth is what really matters. If you are a little off level at the foundation slab (some builders put the foundation slab at a slight angle to control water runoff anyway), I would still go ahead and dry stack the concrete blocks, then make sure your forms are dead level when your pour the hearth.

Would everyone agree with that?
James

[Alan]

1/4" per foot is standard for assuring that water runs in the preferred direction. Something to help keep wood compartments dry seems like a good idea.

If you're worried about the finished structure being visibly crooked, you could choose to use mortar between the lower courses, making up, for example, 1/4 to 1/2" per course until you get it straight then dry stack the rest. You'd probably want to check with someone who knows regarding how thick and thin mortar joints can be and still cure properly.

You could also probably offset successive courses slightly in the horizontal direction. If you're off 1/4" per foot that's about 1/6" per 8" block horizontally. The offsets would be covered by your finish material. The horizontal surfaces of the blocks would still be a little off, but you can easily fix that when you pour the hearth slab.

[CanuckJim]

I've poured quite a few foundations over the years, and it's nice when they come out either dead level or sloped to the degree you want. In practice, this rarely happens right on the money. I'd lay out the first course of blocks, then use shims to bring them up to level. Measure how much you're off on this first course, memorize, then lay your mortar bed to make up the difference. I'd use Type S and brick sand, three to one. In reality, if the weather is with you and your mortar is not too sloppy, you will be able to make up, say, half to three-quarters of an inch in the first course. No worries, the mortar will still set up an cure at that thickness. You can even leave brick shims in place in strategic places, mortared down, not dry. As you go up, course by course, you can make up any small error until you reach level. This niggly method will save you a lot of time and hassle at the slab stage. Block is very forgiving in this way, unlike brick. Just make sure to use a block pointer once the mortar sets up but is not dry. This will ensure that your joints are full and tight.

If you don't have one, buy a line level at HD, line corner blocks (probably have to go to a masonry supply for those), and a good nylon line. Once you're above the first course, set your line level and work too it. Also, a four foot level is a good investment for this sort of work.

Jim