Hiding painted plywood butt jointed seams

[joe1086]

So I volunteered to make my daughter a built in for thier family room. She lives about three hours away, so I'll fabricate at home and bring the components to her house. Everything will be painted.

The configuration is that she has a large recessed alcove about 12' long, 8' high and 24" deep. There will be a bottom row of cabinets the entire length and 3' wide shelving units on each end. The upper center section will have the TV.

I've done a couple kitchen projects, so I'm fine with making the base cabs and shelving units. My question is about the countertop which will be about 16" deep, but the 12' length has me a bit perplexed. Fabricating a solid top would be difficult for several reasons (small shop, 13" planer, no way to haul a 12' top), so I was thinking fabricating the top from plywood in two or three sections. I'll need to assemble the top on site, add wood edging to the front, then prime and paint it.

We want a uniform, solid looking top. Are there techniques to hide the seams in the butted ply and edge banding so they don't telegraph when built and in the future? What type of glue? Should I depress/chamfer the joints and fill? Or other suggestions?

[FS7]

If you're painting, I would use a strap underneath (wood, if you have the room) and screw it from that side. If it's a clean edge and not chipped, you probably wouldn't need to do much of anything besides quick sanding. The seam will disappear.

[museumguy]

I'm doing a home office that has a 105" long top. I chose to make it out of MDF because it will be 1 piece, no seams, no edging. It is painted. I realize that you said that you have no way to haul a 12' top, however, what about renting a 1 way truck? Haul all of the cabinets and a 12' top. Just a thought.

[Cabinet Monkey]

Why not manage the clients’ expectations and put/the seam in an inconspicuous place? 

If they had chosen granite or marble as the top surface they’d have a seam(s) that would be visible and there’d be no discussion about it.  Well , there might be - but it wouldn’t change the fact that slabs don’t come 12’ long.

[joe1086]

Thanks all. I am leaning on making a three piece top with the seams lining up with inner sides of the upper shelf units. The seams should be visable for about five or six inches.

[Willyou]

Thanks all. I am leaning on making a three piece top with the seams lining up with inner sides of the upper shelf units. The seams should be visable for about five or six inches.

Good sensible plan.

[ianab]

Why not manage the clients’ expectations and put/the seam in an inconspicuous place? 

Or, put the seam where it's visible, but matches the rest of the design. Whether it's a painted to match cap strip. Visible but doesn't stand out, or a visible contrast, like a strip of walnut on a light background. Either way it's then part of the design, not a bodge up job trying to hide the fact that the material was too short, or you couldn't actually get the full length into the building. 

As you say. matching the seams to the sides of a shelf unit will work, just extend a strip of the verticals on the shelves down to cover the join. Call it a design feature and carry on. 

Trying to pretend a join doesn't exist usually goes bad over time.

[brianwelch]

We provided a series of A/C plywood display boxes for a 3 week exhibition at a local school of architecture. Boxes were 10', 12' and 14' long. All seams/joints were taped and spackled/prepped (all plywood was skim-coated) for paint. We used an electric hand planer to emulate the taper found in traditional GWB. Owner was pleased...
Granted this was only a limited lifespan, and in a dry environment. I'm sure there are products better suited than joint compound, should you consider this route...