Building a Custom Countertop

[Dennis Putnam]

I am going to be building a custom countertop that will be topped with stainless. The company that will apply the stainless requires I provide the unfinished countertop. That raises a few questions.

1) Should I use 3/4" MDF or plywood (this is for a trailer so weight is a consideration)?
2) I would like to apply bullnose to the front edge but it seems unfinished countertop bullnose is not easy to find (at least not in the big box stores). Where might I look for a local source for this?
3) Is there a similar source for a preformed, unfinished backsplash?
4) What is the strongest method for butt joints (there will be 1 if I use 4'X8' sheets) based on the recommendation for #1? Obviously this will need to be carried around a bit to get the stainless.

P.S. While I have decent basic woodworking tools I don't have Norm's workshop and do not want to spend money on buying special tools that will be used once.

TIA.

[Jerome Stanek]

I would look into Trupan or light weight MDF

[Jim Andrew]

A biscuit joiner works great for butt joints in countertop material. Also the 2nd layer should be offset to support the joint.

[Dennis Putnam]

Thanks for the replies. I never heard of Trupan or light weight MDF. Thanks for that suggestion. As for a biscuit joiner, that is an expensive tool for something I will likely never use again. I don't know what you mean by 2nd layer. Perhaps I need some countertop building instructions. I thought it was just a single layer of 3/4" material.

[Sam Murdoch]

Typically counter tops that will have a covering such as formica or metal are manufactured with some particle board substrate.
The underside perimeter and perhaps on either side of a sink cut out and /or at the location of each cabinet wall underneath (if this info is available) is usually built up with 3" rips of the same material as the substrate. This build up allows for securing safely from underneath without blowing through the finished top with screws and also add to the structural integrity of the c-top. You can move it without it collapsing if you glue and screw the build up strips to the main top. If you must have seams you can use counter top connector bolts (do the google) available through most lumber yard etc.

I guess you could use plywood as a substrate but choose your sheet carefully for flatness. MDF and particle board will come flat and remain flat compared to cheap plywood. FYI - 3/4" thick 4x8 MDF and particleboard weigh in at about - 96 lbs - compared to 66 lbs for the Ultra Light.

[Dennis Putnam]

Ah, perimeter strips. That is what I am missing in my thoughts. Thanks. If I use the same material as a joining block at the seam, only wider, do I really need connector bolts?

What about bullnose and backsplash?

BTW: I found Trupan and interestingly it is 4'X8' plus 1" extra on each side. I wonder why.

[Frank Pratt]

MDF is sold in sheets 1" oversize in both dimensions. It's to allow for kerf waste.

[Sam Murdoch]

Ah, perimeter strips. That is what I am missing in my thoughts. Thanks. If I use the same material as a joining block at the seam, only wider, do I really need connector bolts?

What about bullnose and backsplash?

BTW: I found Trupan and interestingly it is 4'X8' plus 1" extra on each side. I wonder why.

NO - the undermounted blocking will hold it all together - 1- 1/2" min to each side of the joint - attached with glue and screws.

As for the back splash - if this will be a "wet" counter top (a sink installed) I would stay away from MDF. Even particle board will potentially have issues. If the back splash is to be clad with metal it is not likely that the back and bottom edge will have metal surfaces. Even applying to the c- top with a good bead of caulking will not insure that the substrate won't take up water. Wouldn't need much to explode a section of MDF backsplash - a bit more for particle board and quite a soaking to compromise exterior glue plywood that is bedded in caulking.

The bullnose is usually accomplished by the application of the surface material. I would think - BUT DON'T TAKE MY WORD FOR IT - that you only need provide the built up front edge (1-1/2" thick) and the surface material will be formed over that built up front edge.

[John Lankers]

Ultralight MDF is the way to go, I wouldn't touch the regular stuff. For joining panels seamlessly and to attach the bullnose edging I use dowels, I have a Jessem dowelling jig. You could seal the underside and exposed edges with a good coat of shellac.

[Bradley Gray]

Seems like the firm applying the stainless would have specs for this.

I would make certain what their needs are to apply the metal.

[Wayne Lomman]

1. I have always used plywood for stainless substrate. Obviouslychoose the straightest sheets possible.
2. Form your bullnose on the top with a router. Much better than buying something to add on.
3. Same with your splash back. Connect the top to the splash back with a square section timber strip with a Cove routered on one edge.
4. If the top is to stay 3/4 thick, join your sheets with a wide half lap joint or else buy double the quantity of 3/8 sheets and glue it up with staggered joints. This also fixes bowed sheets - glue them with the bows opposing and you end up with a straight board.

If you are going to build up the thickness to say 1 1/2, just glue and screw a 6" strip across the joint. Cheers