When they make concrete countertops they use a different formula for the cement than bag cement. It has a smaller aggregate and more portland. The next question is did you put rebar or some wire mesh in the cement too? If the top ever cracked it could suddenly collapse with no metal in it.

Your construction is sufficient so long as the joints are glued and nobody tries to move the table without putting air under it.

 

I don't see any triangulation of the legs and skirt to prevent racking, i.e., the collapse of the legs into a parallelogram.

The 2X4 skirt even with bolts won't be up to keeping the legs from leaning. A much deeper skirt, or a complete boxing in of the base with plywood, or at least some diagonal cross braces are going to be necessary.

 

I think that mortise and tenon joinery with a drawbore would do a much better job of keeping it from getting loose and racking. I am doing a through tusk tenon with a drawbore on my workbench. Granted, at about 350 lbs, it is only about 1/2 the weight of yours, but there is no possible way that the legs are going to come loose.

For reference, my bench top is 5" thick SPF, 2' wide and 8' long. The legs are 5"x4 1/2".

If I were doing it, I'd laminate three 2x4s together building in mortises and tenons ... something along these lines. It's a good bit of work, but it would be more than strong enough, and steady as a rock.

 

Thanks for the replies..

I used the concrete made for counter-tops (Sakrete 5000) and put re-bar inside of it. The top should be good and solid.

So for the bottom of the base, how about if I put turnbuckles going diagonally from the end cross-members up to the bottom center of the table? Kind of like the image attached? Or should I use 2x4's from the end cross-members to the center of the table instead of turnbuckles?

Thanks!

 

For what it's worth, this is how I designed mine ...

 

Thanks Chris.
Like the design, but the bottom two trestles would be in the way of the chairs and people feet. Which is why I moved the trestle to the center. What if I used two bottom 2x4 trestles in the center spaced about 3" apart?

 

Also, do you all think Redwood or Cedar would be a strong enough wood type for this? Or should I go with Pine or Douglas Fir?
Thanks!

 

Given the weight you would be better off using yellow pine. Douglas Fir would be next followed by whitewood pine. I wouldn't use cedar and I especially wouldn't use redwood. Structurally redwood is very poor. It breaks and splinters very easily.

 

Ok. Good to know about wood. However, would 6x6 legs from cedar be okay due to the thickness?

Thank you.

 

The thickness of the legs isn't so important since the table is less than 3' tall. The issue is lateral movement. if the joints are solid enough 4x4 cedar legs would be more than sufficient. What 6" legs would help is to give more surface area to fasten the skirts to in order to straighten the joints. Still I don't think there would ever be a problem unless someone attempted to scoot the table. That would put all the weight of the top against the joints.

 

I see. So if I'm going to notch the legs for the trestles, I should go with a 6x6. If I'm going to straddle the legs, I should go with a 4x4.

 

All that matters is the joints stay together. When using 6x6 posts on an outside structure such as an arbor the issue isn't the vertical weight it's wind blowing at the structure. If it wasn't for the issue of wind the structure could be made with 4x4's for the posts. It's the same with your table. You don't have a care in the world about the vertical weight, it's someone leaning on the table or someone trying to push the table. As long as the joints are solid you could use 2x4's for legs.

 

Great way to describe it. That is why I was recommending a mortise and tenon type of joinery. M/T joints have a mechanical resistance to slipping under side pressure. Even M/T joints at just the top (with 2x6s) would never give way to side pressure.

 

Oh I see. That makes sense. Thank you for the info. Think I'll go with 4x4's to save space.

 

Just curious about how you are going to get it in the house? 700 lbs is quite a bit of weight, better make sure your foundation will handle it LOL

 

I am estimating about 700lbs since I used 8 bags of 80lb mix. I am hoping 700lbs spread over 8 ft will make it more manageable. I will have 4 strong guys helping me.

 

I will use the upper version of M/T. But the lower part I will need to redesign to accommodate leg/foot room.