36+ Pompeii in St. Louis

[merk]

Re: 36+ Pompeii in St. Louis

Concrete forms work today (contractor)

[Bookemdanno]

Re: 36+ Pompeii in St. Louis

If the Concrete slab is your finished surface, then i'd set a fall outwards from the centre to all sides.

[merk]

Re: 36+ Pompeii in St. Louis

LOL. Contractor arrived about 30 minutes after my previous post. Hearth might be poured this afternoon.

[merk]

Re: 36+ Pompeii in St. Louis

Not too much progress over the weekend. We mostly worked on landscaping before winter hits. The larger patio requires us to transplant a bunch of plants.

The HardieBacker thing was bugging me so I popped it out and went with plywood. It came right out with a few taps of the sledgehammer. The whole thing took me about 2 hours so I'm happy and won't worry about. In STL I'm sure that board would experience the full range of temps and humidity. I'd rather have it right and move on. [Note: you can see the glue that was holding the backer board. that is not caulking]

Next, the contractor/neighbor is pouring the hearth slab. I gave him the green light this morning and he acts fast.

Question: Should we do a slope/grade on the hearth slab? Being in STL this oven will see some weather. As I said before, I want to avoid doing an enclosure/roof so should we do a 1% grade? if so, which direction etc? Any input is appreciated!

Matt

[stonecutter]

Re: 36+ Pompeii in St. Louis

Just cut it with an angle grinder after you brace it from the bottom...then remove it afteryou pour the slab.

[merk]

Re: 36+ Pompeii in St. Louis

I used cement board under my slab. I didn't feel like messing with the plywood. It seemed a lot easier to place the board and just leave it there. I have a divided base, but I still used a little shoring under the cement board.

My problem is that i used HardieBacker and not something intended for exterior use. I see your photos and I did it the same way (laid the board on TOP of block wall with room for concrete to surround the edges as it is poured).

I don't want this stuff to disintegrate under the hearth in 5 years so I'm leaning toward busting it out.

[bobmurphy]

Re: 36+ Pompeii in St. Louis

I used cement board under my slab. I didn't feel like messing with the plywood. It seemed a lot easier to place the board and just leave it there. I have a divided base, but I still used a little shoring under the cement board.

[stonecutter]

Re: 36+ Pompeii in St. Louis

I meant that hardiebacker was the lazy route. Just pour and leave it there.

I don't know about lazy...it is less work but not in a bad way IMO. Nothing wrong with doing that way, just that the material (HardiBacker) is not appropriate for an application like that.

[stonecutter]

Re: 36+ Pompeii in St. Louis

I meant to say, don't trash the HardieBacker....since you have it already. Use it for the form, but break it out afterward, and don't encapsulate it on your block beam. Cut it to the inside, as recommended for plywood or osb sheathing.

[merk]

Re: 36+ Pompeii in St. Louis

What's lazy...plywood? That is just standard form material, and you don't need permanent sheathing like Durock under the slab.

Cut the plwood or osb to fit to the inside of your block so it doesn't get jammed when you drop it out.

I meant that hardiebacker was the lazy route. Just pour and leave it there.

[stonecutter]

Re: 36+ Pompeii in St. Louis

What's lazy...plywood? That is just standard form material, and you don't need permanent sheathing like Durock under the slab.

Cut the plwood or osb to fit to the inside of your block so it doesn't get jammed when you drop it out.

[merk]

Re: 36+ Pompeii in St. Louis

You should not use HardieBacker for exterior applications, it is an interior product. Use Durock or a plywood form instead. Consider perimeter support for the pour, around the center column. A central support is not enough and you will get a bow in the slab.

Should I trash the hardiebacker and go with a standard plywood? Somewhere on this forum I saw that idea and thought it was smart (lazy).

[stonecutter]

Re: 36+ Pompeii in St. Louis

You should not use HardieBacker for exterior applications, it is an interior product. Use Durock or a plywood form instead. Consider perimeter support for the pour, around the center column. A central support is not enough and you will get a bow in the slab.

[merk]

Re: 36+ Pompeii in St. Louis

I decided to go with a center support column and 1/2" HardieBacker. The board seam is centered on the column. I glued everything excessively.

If anyone sees a problem here please let me know. I'm assuming the concrete load with not exceed the limits of the board/column.

[merk]

Re: 36+ Pompeii in St. Louis

Thanks! I was just researching FB board and blanket. Will check out Hi-Temp