Support 1000lb Soapstone Overhang?

BrentMarch 5, 2012

Hi,

I'm looking for help here. We currently have a very large overhanging laminate countertop which is supported by two corbels attached to a pony wall. We want to replace it with a 3cm soapstone counter (~40 sqft = 1000lbs.) We don't think our current corbels will support the whole counter sufficiently and are looking for ideas on how to support this without adding legs, if possible. The widest part is overhanging the pony wall by about 38'. The overhang from the end of the corbels is about 13'. There is a large span (~ 44') between the corbels. Does anyone have any ideas how we could do this? We'd really like the soapstone on our upper counter.

Here are some pictures to hopefully give you a better idea of what we have.

Sorry for the size, don't know how to make them smaller.

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live_wire_oak

You need a steel fabricator to create a box beam support frame inset into the pony wall and bolted to it. And make sure the pony wall is well joined with lag bolts into the floor joists.

    Bookmark   March 5, 2012 at 4:57PM
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clarygrace

Most stone fabricators will not install overhang over 10", max 13" depending on the stone, without additional support. I believe that is the standard. Live_wire_oak is right, you will need addtitional support framing.

    Bookmark   March 5, 2012 at 5:29PM
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beekeeperswife

Here is a very informational thread from days gone by..

Here is a link that might be useful: Stone Thread

    Bookmark   March 5, 2012 at 5:57PM
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marcolo

I would never trust that overhang unless the pony wall were ripped open so you could examine its construction or rebuild it. There is no countervailing weight--all the stone is hanging on one side. It would kill anyone sitting there if it fell.

How about a beautiful wood top?

    Bookmark   March 5, 2012 at 6:01PM
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Angie_DIY

I am going to go LWO and Marcolo one step further. It obviously needs stout support, and I agree the pony wall needs to be looked at, but I think the services of a structural engineer are in order for this. As Marcolo points out, all the weight is hanging out to one side. There will be a tremendous torque on the members of the pony wall. Even stout support lagged to the joists may not be enough to resist this. And it is quite possible to twist the joists sideways if the cross-bracing is insufficient.

    Bookmark   March 5, 2012 at 6:23PM
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Dando

I'm sorry, I don't see 40sq/ft or 1000lbs.
You're just talking about the upper counter, correct?
If this idea was presented to me, I'd want two things.
1) Legs shaped like your corbels. You have two corbels supporting the top off of the pony wall. I'd want two more supporting the pony wall off of the floor. BUT, built as two legs...instead of four corbels.
2) 3/4" Plywood countertop underneath the stone. With a pretty edge, and, stopped 6" from the edge of the stone.

    Bookmark   March 5, 2012 at 6:35PM
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Angie_DIY

I'm sorry, I don't see 40sq/ft or 1000lbs.

Try counting the squares. (The ones evident in the picture are evidently 2.5" on a side.) I came very close to 40 sq. ft. I got about 38.7 ft^2, which should be about 850 lbs., give or take.

    Bookmark   March 5, 2012 at 7:53PM
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Brent

Thanks all for your quick responses, I really do appreciate them.

We have a contractor and a finishing guy coming over, at some time, with the stone fabricator to have a look at what we are wanting to do.

I will probably remove the drywall from this pony wall to see if it is indeed afixed into the floor joists, but I will wait for the opinions of you fine folks and the contractor's determinations. If he says that it is a no-go, that will be it for the soapstone on that overhang.

@live_wire_oak

Yes, I believe that I will require some kind of metal brackets. I've chased this idea all over the web with no luck. I've even E mailed Chemical Concepts, and they cannot help us with any of their brackets.

@ clarygrace,

The stone fabricators didn't seem that this slab would be a problem with the corbels in place; it just didn't seem right by me. I also didn't want a slab sitting on my kitchen floor looking for a make -do support after the fact.

@ beekeeperswife,

I have read that thread many times, before deciding on soapstone, but unfortunately, I'm dealing with a larger overhang.

@ marcolo,

I totally agree with you, that is why I'm approaching the experts here. That slab would probably just peel off the wooden corbels from that pony wall.

@ Angie_DIY,

A structional engineer is probably the go-to person, I'm not getting a good feeling about the amount of weight of this part of the overhang, or how I would overcome the forces in volved.

@ Dando,

The rounded part of the overhang (left on the diagram) is roughly 43" by 86" long, while the remaining area (above the stove along the 52" pony wall shown on the diagram) adds another 36" by 48" until it narrows to a 17" overhang (also shown on the diagram). The 17" part of the overhang will be dealt with separately

The 40 square feet (combines both those areas), @ 3 cm thick, @ (least 22 lbs/ft.). I figured it would be around the 800 lb. mark, the fabricator said 1000 lb; I don't know if there was a margin of error for someone standing on it, but a good safety margin is good by me.

My aim was to support this weight without anything touching the floor, but I would entertain something creative and decorative, as well as non-intrusive.

Thanks very much for further input and your help.

    Bookmark   March 5, 2012 at 8:26PM
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itsallaboutthefood

Our soapstone (3cm) overhang is supported by steel bars which are imbedded in the stone. The fabricator routed out the stone for the 1/4" thick steel bars and then "glued" them in. Here is a picture: From Soapstone

    Bookmark   March 5, 2012 at 9:14PM
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itsallaboutthefood

I just realized that your overhang is behind your stove. This is different than ours...the steel bars go across the cabinets in front of the overhang in our case.

    Bookmark   March 5, 2012 at 9:16PM
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Brent

@ itsallaboutthefood

It might not be evident, but the overhung countertop is higher then the countertop beside the stove by 5 1/2", all of the weight of the soapstone would be only on one side of the pony wall.
Although of note, we're also replacing the lower countertop with the same soapstone.

    Bookmark   March 5, 2012 at 9:28PM
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Dando

Count the squares?
That is one big stovetop.

ALTHOUGH, I don't see that as the problem.
400lbs or 1000lbs..either will put the hurt on that pony wall. Plus, a slab of stone that size will need underlayment out to 6" or so from the edge.
I think curved legs would look good.
With a 24" long foot (floor imprint length) on the leg. It would be way back under from the edge.

    Bookmark   March 5, 2012 at 9:30PM
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live_wire_oak

I just have to ask why you want such a large overhang? At bar height, you only need 12" of room for your feet. This isn't a 30" high table where you're going to sprawl out and lounge. You'll perch with your feet tucked under you on the bar stool rungs.

42" of overhang is complete and total overkill for any real world usage.

    Bookmark   March 5, 2012 at 9:45PM
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zartemis

We had overhang concerns in our install (but nowhere near as demanding scenario: 18 inch overhang on two sides, no corbels, but the center line was over cabinets). We considered tubular support, but couldn't find a local specialist to assist with design. We did find these folks in North Carolina who appear to have experience with tubular supports. Here is one of their projects:

We did contact them and at the time they were willing to consider remote design services to provide drawings we could give to a steel fabricator.

In the end, we decided on 1/2 inch steel plate from a fabricator who had lots of experience doing such installs (covering near the entire surface, not strips), bolted down through the cabinets with cables to the floor joists (we wanted to have extra protection in case of major accident: say someone heavy jumping on the overhang, making the center of balance no longer over the cabinets, possibly ripping the steel off the cabinets. With the cable, the countertop may fracture (steel plate can flex more than tube steel), cabinets may get damaged, but no one should be injured by 100s of lbs of tipping/falling stone and steel unless all 3 cables snap or major structural fail of the reinforced cabinet box). Because of the weight and cost of the steel, we also downgraded from 3cm soapstone to 2cm granite to save a little (in both weight and dollars).

Here's our install. And it's only a 4 foot by 6 foot peninsula and overhang is 18 inches on two sides:

Under counter view:

Top view:

Lack of legs or corbels was important to us because there are wheelchair users and friends with disabilities limiting the bending of their legs. Height is 34". We find 18 inch sufficient. There is an occasional light kick of the cabinet underneath -- I wouldn't want less overhang -- but otherwise it's adequately spacious. Those cables run in dedicated chaseways in the cabinets themselves and the entire cabinet is also bolted to extra framing in the peninsula wall. This may be overkill for our situation, but we wanted overkill for safety.

This was our solution for a less demanding scenario. Keep in mind you don't have vertical support anywhere near the center of balance, but you could if you gave up overhang depth.

    Bookmark   March 5, 2012 at 11:00PM
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Brent

@ Dando,

Yes, it's a large stovetop. The leg idea is a good one if we decide to go with feet, which we are trying to avoid at the present.

@ live_wire_oak,

What is laid out in the diagrams, is what we presently have, it's just out of laminate, instead of soapstone.
This is our "kitchen table". We eat most meals here; we also have a formal dining room away from this area.
If we can have it, then, why not?

@ zartemis,

Thanks for the link, we will check it out.

Thanks all for your replies and help.

R.

    Bookmark   March 6, 2012 at 1:20AM
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davidro1

from the floor to the metal support structure, you need a few L braces; don't rely on lag bolts alone.

    Bookmark   March 6, 2012 at 9:27AM
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Brent

If we get a final determination and go with the soap stone on the upper eating area, I will post it here (with pics, of course). The rest of the area is pretty much a standard stone project.

Note: I've been here for years, I usually post in the soap forum and some others when I can help.
Thanks all.

    Bookmark   March 6, 2012 at 10:25AM
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cloud_swift

That is a huge overhang (it will take quite a long reach to clean the center of it) - especially in a situation where the granite ends at the supporting wall so there is no counterbalancing weight like there would be on stone that extends over cabinets. A fabricator that thinks your corbels would be enough is scary.

In the picture with the chairs, it doesn't look to me like there is 36" of overhang like your diagram shows - are you sure of the measurement?

If there is 36" of overhang, you could put 12-18" deep cabinets under it - for things like holiday items that you don't need to get out that often - and still have a generous 18" overhang. If not, I think a structural engineer is a good idea.

    Bookmark   March 6, 2012 at 11:05AM
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davidro1

The base cubic structure will be subjected to a different set of stresses, compared to the norm. Stresses to which kitchen cabinet base cubes normally are subjected are not lopsided like this. For this fact alone, you must move to a metal structure, of the type defined by live wire oak. Key words for web search are box beam box girder. (Wikipedia: "Compared to an I-beam, the advantage of a box girder is that it better resists torsion.")

in the remodeling forum someone opened a thread about a situation similar to yours. The link to the wood subfloor will be the weak link. This is why I mentioned metal braces under the floor. Bolts are not reliable under the stress that this counter setup will create. Bolts will crack the wood. Braces will distribute the force appropriately.

But, take no one internet person's word for it. Double check elsewhere.

Here is a link that might be useful: L brace at floor level

    Bookmark   March 6, 2012 at 11:32AM
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Brent

davidro1,

Yes, this is along the line of thinking that we have to go.

Going with metal brackets, possibly some tubular pony wall enhancement, with some structural engineering involvement.
I had search the net for something on-line to buy, and I came up empty handed.

Fortunately, we do have some, although limited, to the underside of this area (not sure how much), so we might be able to have a look at the floor structure.
I appreciate all of the help.

    Bookmark   March 6, 2012 at 2:58PM
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tubeman

Try Federal Brace. They will design the supports for you as well.

    Bookmark   March 6, 2012 at 4:59PM
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GreenDesigns

Why not take down part of the pony wall so that the whole thing is one level. That would help a lot with the cantilever problem because then part of the counter would rest on the cabinets and act as a counterweight. Counter height seating is more comfortable than bar height. You can just cut your stools down. Also, 42" of overhang is about two feet more than is actually usable even if you have Shaq hanging out with you. Reduce the overhang. It's not adding any positives to the situation, only problems.

If you do both of those things, then conventional available support like the Counter Balance system are available off the shelf.

    Bookmark   March 6, 2012 at 5:51PM
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Brent

@ tubeman,

Thanks for the Federal Brace link, it didn't come up in my search for bracing links.

@ GreenDesigns,

We like the plan (and our present configuration) that we are seeking help for.
This is a large area, kitchen/family room is wide open, 20' by 28', having everything at or about the same level, counters/furniture/appliances/window ledges (we have about 28' long of floor to ceiling windows), would not be to my liking.

I would keep the laminate at present level before changing the upper countertop to a lower level with soapstone. This part is only part of the total upper overhang, the rest of it is straight forward as far as supporting it.
I understand the concept of support for the normal overhang construction, it is the tremendous slab weight and the engineering/anchoring of the pony wall that I had not found in my internet searches.

    Bookmark   March 6, 2012 at 11:11PM
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garyvp

I am building a 26" wide by 90" long x 36" tall island with a 3cm hard soapstone top supported by a 30" cabinet on one end and 4" steal pipe flanged at each end and which bolted to the floor. The 42" open span is supported by a 3" x 12" x 55" aluminum channel covered with a slightly larger 1/2" ply as a bed for the stone. The aluminum is vey strong and easy to work with and looks very good, and it does not interfere with seating either. The stone is cantilevered 7" on each side appears to float.

I think the use of structural metal is the way to go.

    Bookmark   March 8, 2012 at 10:41PM
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Brent

Update (if anyone is still reading),

The contractor and the stone fabricator determined that the corbels that we presently have will do the job, these did not flex at all under a test stress.

The soapstone will have the steel reinforcement spanning from and between the corbels; the 2 large ones we presently have and 3 more for the straight run (not shown) in our diagrams. This 9' x 17" straight run (also on adjoining pony wall), will assist in anchoring the weight of the eating area, as well as the cabinets on the other side of the overhung soapstone by the stovetop.

Note: Under this area we have 2 beams running parallel (4' each side of the pony wall) of the overhung area; it's well supported.

Templatting is scheduled for end of April.

R.

    Bookmark   March 11, 2012 at 2:34PM
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GreenDesigns

I'm curious as to what type of "stress test" was done? Also how was it determined that the pony wall was sufficiently connected to the floor joists?

I really fear that the salesmen here are setting you up for disaster.

    Bookmark   March 11, 2012 at 2:51PM
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Brent

GreenDesigns,

I have faith in these people, the stone fabricator is a well known fabricator who is fairly well known in the North American stone indrustry (I've learned this after our last meeting and checked what I could on the net), as well visiting some of their completed projects and talked with home owners, some also x-neighbours.
The contractor is a high end builder with many years under his belt and was a neighbour of ours.

I do understand your concerns, I did have some of the same when starting this project, after talking to them, I have complete confidence that they have my best interest.

    Bookmark   March 11, 2012 at 4:09PM
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garyvp

Nice thread, y'all. Very helpful.

Just finished a 26" x 90" island supported on one end by a reinforced 30" IKEA cabinet with the rest mounted on a 3x12 aluminum channel beam supported on a 4" pipe column. The stone cantilevers 7" on either side of the beam. It is rock solid and is not bolted to the floor.

See the pix

    Bookmark   May 23, 2012 at 2:34PM
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Brent

The soapstone is in. The corbels that we used on the eating area, is the large ones that were already in use by the laminated countertop that we had before.
For those interested; the corbels were on the horizontal 24" by 33" down the pony wall.
They were a 2" x 4", both on the horizontal and down the wall; these were sandwiched by chip board (on both sides) screwed into the 2" x 4", then covered on the 3 exposed sides by 1/2" drywall.
With the soapstone on it, it does not move at all.
On the long side 9'or so, the 3 wooden corbles that we made out of 2" red oak keeping the shape of the large corbels are rock solid as well.

    Bookmark   May 28, 2012 at 8:12PM
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Brent

OK Folks, here are some pictures of the completed kitchen.
This first one shows the bare corbels after we took the old laminate counter off. We used the same corbels to support the soapstone.

This is the eating area which extends 13" past each end of the two (2' long) corbels.

This is the 9' long raised bar.

This shows the undercounter LED lights which are inset into the soapstone overhang all along the pony wall on both sides (for a total of 33').

    Bookmark   June 29, 2012 at 10:50PM
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lwerner

That looks wonderful! I like the way you had the LEDs behind the cooktop recessed into the countertop above it. And the big, curved end of the peninsula is a great idea. It looks nice and gives you lots more counter space too.

What wood are the cabinets? Natural maple? That's probably my favorite wood for my woodworking hobby.

What type of soapstone is that? I haven't seen that one before. I think it's the first one I've seen that has dark veins in addition to light ones. And it appears to have a little bit of a greenish tinge, though that may just be my monitor. It looks like it might go really well with the cherry cabinets I'm considering.

Laura

    Bookmark   June 30, 2012 at 5:04PM
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Brent

Laura,

Yes, the cabinet fronts are solid maple, some of them are figured and some are flamed. The tops are all doors and the bottoms are mostly drawers.

The stone is called silver soap stone from Brazil, but it is really a dark green for the most part, and has no silver in it.

    Bookmark   July 1, 2012 at 1:47AM
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