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Concrete foundation thickness (any pros?)
Posted on 3/9/25 at 5:44 pm
Posted on 3/9/25 at 5:44 pm
How thick would a concrete foundation base for a 5,000 pound fireplace need to be? Houston with heavy clay soil.
5
Posted on 3/9/25 at 6:17 pm to DukeSilver
thickness, 5" would be enough with WWF or rebar. (a contractor will probably pour thicker, but that's not really necessary. the 5000 lb won't be a point load or dynamic)
that's not the question though, it's the area of the footing you need to address. heavy clay may have a capacity of 2000 lbs per sq foot or greater. so in theory, a 4 x 4 foot pad could carry 32, 000 lbs.
assuming the clay is undisturbed and or compacted if needed.
that's not the question though, it's the area of the footing you need to address. heavy clay may have a capacity of 2000 lbs per sq foot or greater. so in theory, a 4 x 4 foot pad could carry 32, 000 lbs.
assuming the clay is undisturbed and or compacted if needed.
This post was edited on 3/9/25 at 6:25 pm
Posted on 3/10/25 at 7:39 am to Jmcc64
Please don't put WWF or rebar in 5-in. concrete.
Posted on 3/10/25 at 9:05 am to CWS91
quote:
Please don't put WWF or rebar in 5-in. concrete.
Don't as in it's not necessary?
So a 5" slab is enough, how about the footer?
Posted on 3/10/25 at 10:27 am to DukeSilver
the bucket on a mini excavator is 24" wide.
two scoops makes a 24" deep trench. if it were mine i would plan on a 24" deep foundation for the fireplace/chimney, extended 6" min around the perimeter of the masonry
you are assembling structural concrete not a patio
two scoops makes a 24" deep trench. if it were mine i would plan on a 24" deep foundation for the fireplace/chimney, extended 6" min around the perimeter of the masonry
you are assembling structural concrete not a patio
Posted on 3/10/25 at 10:40 am to DukeSilver
why are you not getting an engineer to stamp your foundation plans?
at minimum, you want a footer into the existing compacted ground around the perimeter...
at minimum, you want a footer into the existing compacted ground around the perimeter...
Posted on 3/10/25 at 11:02 am to Randall Savauge
quote:
why are you not getting an engineer to stamp your foundation plans?
at minimum, you want a footer into the existing compacted ground around the perimeter...
For clarification.
This is an outdoor free standing fireplace with that will be incorporated into an outdoor patio/grill area.
I plan on DIYing it with the occasional help from buddies/neighbors with these plans with minor midifications. Backyardflare
This post was edited on 3/10/25 at 11:20 am
Posted on 3/10/25 at 11:05 am to DukeSilver
gotcha, then i would go with what the poster above said and add a 24" grade beam all the way around. if the rest of the outdoor paving isn't supported by grade beams, also consider installing an expansion joint between the non-structural concrete and the fireplace foundation in case they settle at different rates.
Posted on 3/10/25 at 11:55 am to DukeSilver
I have a 4” thick slab. But concrete cinder blocks were placed in the fill around what would be the area of the stone fireplace to carry its weight. I also have a large great room. Cinder blocks in the fill were also used under what would be the load bearing walls.
Posted on 3/10/25 at 12:45 pm to Jmcc64
5-6” thick will support a car. So you’re probably good there.
Posted on 3/10/25 at 2:51 pm to DukeSilver
For a 5000lb fireplace you don't need grade beams or a "footer" (hate that word)...your focus needs to be more so on ensuring you have a wide mat to support this fireplace that is bearing evening on soil (assuming your yard is pretty flat).
A rectangular foundation that keeps your loads centered, about 5-6" inches on the thickness, at least one layer of welded wire mesh or rebar not laid on the ground but mid depth, and properly compacted soil beneath will be plenty for this DIY project to keep cracking to a minimum.
Edit: Is this to be anchored into the concrete or unanchored?
A rectangular foundation that keeps your loads centered, about 5-6" inches on the thickness, at least one layer of welded wire mesh or rebar not laid on the ground but mid depth, and properly compacted soil beneath will be plenty for this DIY project to keep cracking to a minimum.
Edit: Is this to be anchored into the concrete or unanchored?
This post was edited on 3/10/25 at 2:52 pm
Posted on 3/10/25 at 3:16 pm to Adam4848
quote:
Is this to be anchored into the concrete or unanchored?
I am just doing the initial research, so which ever is better.
I have an existing patio. Was planning on pouring this foundation right up to the current one but separated by an expansion joint. It's going to be an L shape with an attached grill and counter top.
It will look different than this, but the below is close enough for an idea of what I'm going for.
I'm actually going for the same look as Matt Risinger's backyard. I can't find a still but if you pause this youtube video at 25:43 that's pretty much what I'm going for.
This post was edited on 3/10/25 at 3:18 pm
Posted on 3/10/25 at 3:48 pm to DukeSilver
you can pour 24” on something like that and still not use 3 yards. Cheap insurance. Form guys won’t care they’ll be out there the same amount of time
Posted on 3/10/25 at 5:01 pm to DukeSilver
quote:
I am just doing the initial research, so which ever is better.
There's going to be enough self weight that you don't necessarily need to anchor.
Posted on 3/12/25 at 2:31 pm to DukeSilver
If the fireplace is not laterally supported above grade (at least half the overall height) you will need a wide enough matt to resist overturning from wind loads.
Posted on 3/12/25 at 3:05 pm to junkfunky
quote:
If the fireplace is not laterally supported above grade (at least half the overall height) you will need a wide enough matt to resist overturning from wind loads.
Interesting, hadn't though of that.
Do you think the side that is "touching" the existing slab is supported by the existing slab? And therefore just need to make sure the "back side" of the slab that the fireplace will sit on is a foot or 2 wider than the fireplace itself?
Posted on 3/13/25 at 3:04 pm to DukeSilver
Whatever concrete the fireplace is sitting on will help distribute the load.
What he was referring to is don't have the fireplace flush against the edge or concrete, allow for 1-2' feet overhang on all sides at least.
What he was referring to is don't have the fireplace flush against the edge or concrete, allow for 1-2' feet overhang on all sides at least.
Posted on 3/13/25 at 3:16 pm to Adam4848
quote:
What he was referring to is don't have the fireplace flush against the edge or concrete, allow for 1-2' feet overhang on all sides at least.
Gotcha
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