Pour two slabs at once?

[Tomweb]

Hi all,

I'm hoping to pour here in the next few weeks, thanks all for participation on this forum, it's invaluable!

Here's a thought. I'm considering a truck pour in a few weeks. How outrageous would it be to have the foundation slab _and_ hearth base poured at the same time?

I'm planning to frame the hearth base, resting it on 4 x 4s on the ground nearby, where I'll screed, finish, level and cure......A couple (?) weeks later I'll use my front end loader to web sling it onto my block supports?

It'd be a gentle operation but I feel it could be done properly and safely with a few extra bodies....

I see a possible savings of several hours and it takes advantage of having the truck in place.....once....., as a newbie I should ask: ."...what am I missing here?"

[lwood]

Re: Pour two slabs at once?

The perlcrete mix is a little strange to work with but it may be possible. Better have the first slab well supported.

[GianniFocaccia]

Re: Pour two slabs at once?

As long as you have the lift, it sounds like a practical project. I would pour the support slab with 90 degree bends in the rebar (pointing down) around the perimeter. This way when you lower your slab onto your blocks the rebar drops into the top-most concrete-filled course.

[lwood]

Re: Pour two slabs at once?

Why not pour it in place?

[brickie in oz]

Re: Pour two slabs at once?

I see a possible savings of several hours
...what am I missing here?"

Your going to risk your build for a couple of hours?
What am I missing here?

[Tomweb]

Re: Pour two slabs at once?

Iwood, My reasoning has to do with efficiency. I figure while the truck's here I'll go ahead and double pour.
You also bring up a point of discussion regarding your perlcrete comment

The perlcrete mix is a little strange to work with

My approach was going to be hearth slab followed by insulation layer, I better drop back and review suggested techniques.

John, thanks for the bent rebar suggestion, I like that idea!

[jeeppiper]

Re: Pour two slabs at once?

sounds ambitious!

1. Did you estimate the weight?

2. Once you drop the slab on top of the foundation, how will you get the slings out from underneath?

3. Is your hearth slap just the pearlite mixture? Doesn't seem structural even with the rebar. Or will you have a structural slab supporting a pearlite mix?

4. Can your front end loader "reach" far enough to center the slab over top of your foundation base?

Gut reaction is not to rush it and do it in two pours.

I had a truck pour my foundation...and I used bags for the hearth.

[Gulf]

Re: Pour two slabs at once?

I'm planning to frame the hearth base, resting it on 4 x 4s on the ground nearby, where I'll screed, finish, level and cure......A couple (?) weeks later I'll use my front end loader to web sling it onto my block supports? "

I would form 4 pad eyes out of rebar and wait at least 28 days before placing it. The hearth slab will be much stronger then and considerably lighter. After placement, the pad eyes could be cut off even with the slab.

[Tomweb]

Re: Pour two slabs at once?

Bricke- Iwood- Gulf- Jeepiper!

All good questions…..here’s what I figure.

With _great_respect and admiration for all who have completed the task and are enjoying the fruits of their labors……I don’t think I’m risking my project to save two hours. If, after discussion and serious consideration this idea is flawed, I’ll drop back and make two separate pours. Don’t we all look at our tasks and projects with an eye towards efficiency whenever possible?….If I can have the hearth slab in place, ready for an insulating layer and firebrick after a month, I’ll be stoked! (Pun intended...)

First, my plan is to pour a concrete hearth slab with an insulating layer over that, either a perlcrete mix or appropriate foil faced foam boards

Second, regarding weight: I have calculated the following: My 6 x6 x 4” hearth slab measures out at about 12 cubic ft and will run about 1700 lbs ( Yes, my loader will handle load and reach…but very good questions)

Here are my weight calculations, based on SakreteWould not a poured mix be very close in weight?...I'll call the delivery guys and ask that one...) 80# bag of Sakrete is .6 cu ft… 12 cu ft would require.20 bags = 1600 lbs + rebar…. I’m thinking 5/8”, probably 5- 6ft pieces and 5 -7’ pcs for a total of 65 ft @ 1+ lb / linear ft = 70 #
Gulf - good thought on curing time. I knew it could use a good, damp couple of weeks. Of all the caution I exercise, letting the slab cure properly is my best bet to avoid a fracture on sling day…….btw your album is awesome, I’ve been through it a number of times to try and know what I think I know….. and will return again, I’m sure!

Once you drop the slab on top of the foundation, how will you get the slings out from underneath?)

...............Jeepiper. I hope I don’t “drop” the slab at all!!! I figure load slings in two places that’ll allow me to set it in place, supported by the extended rebar….right? As this slab is gently set in place I plan to pull the straps out from around the slab. I’ll lower the bucket and the web slack will allow me to pull the straps, as there will be approximately a 1” gap between hearth slab and supporting block.

You all are great….Thank you for helping me work through this again in my head. I’ll keep you posted and stay in touch! Many thanx!

[brickie in oz]

Re: Pour two slabs at once?

appropriate foil faced foam boards

It'll melt.

[Bacterium]

Re: Pour two slabs at once?

Tricky but you will probably hear our loud applause if you pull it off

[mrchipster]

Re: Pour two slabs at once?

As to slinging the load why not bend some rebar into loops and hook around the internal rebar. Extend the loops above the slab and put straps through the loops to move the slab.

After the move cut off the rebar loops.

Chip

[Tomweb]

Re: Pour two slabs at once?

Maybe a poor choice......

[david s]

Re: Pour two slabs at once?

sounds to me like your plan is a whole lot easier than building formwork around the top of the stand. When you pour the supporting slab it is a good idea to slope it slightly downwards towards the corners ie a hump about 1/4" higher in the middle, to avoid water penetrating between the supporting slab and the insulating slab.

[Tomweb]

Re: Pour two slabs at once?

Sorry guys...The 'Poor Choice' comment was in response to brickie's very concise..."it'll melt" regarding my mention of possibly using foam below the hearth....oughta know better, I've been lurking long enough!

Thanks Al..!