Joining plywood or hardwood for long countertop

[Greg Bieg]

Currently I am working on a part of our finished basement for a play area for our kids. I am repurposing some shelves and cabinets for storage.

Along one wall there will be cabinets and I want to put a long wood countertop across all the cabinets. The length is about 13 feet and the width would be around 16 inches. The whole unit will be painted white.

I’ve joined some boards before but with varying success of hiding the seam to give it one long continuous look.

Any suggestions? Thanks! First time poster.

[Mike Henderson]

Welcome to the forum, Greg. I'm afraid I'm not much help because when I join boards end-to-end I always wind up with a seam that shows, even under paint. Especially over time. It may look good when I put the paint on, but later the seam telegraphs through.

Maybe someone else will have some good ideas.

Mike

[Edwin Santos]

Counter bolts are the standard choice for jobs like this. I like the Fastcap flipbolts. Rout the recesses so that the bolts are at or near the center of the material thickness. Not hard to make your own template, but Fastcap sells one if you prefer.

[Bill Dufour]

Buy a premade laminated kitchen countertop from the borg. If their max length is too short, join two with the special bolts+ hardware sold next to the counters.
Bill D.

[Edwin Santos]

Pre-made IKEA kitchen countertops are a good value too. But at 13ft, you'll still need to make a joint.

[Patrick Walsh]

Dominos and pipe clamps.

We do it all the time at work to join plywood panels.

Lamello also sells some pretty nifty connectors for such applications.

I think eleven festool is selling some kind of insert Allen key thing for the domino xl now?

Regardless the seam will telegraph through at some point so just try and put is somewhere inconspicuous..

[Wayne Lomman]

Joint whatever way as the other guys suggest but glue with epoxy. When you sand the joint, leave a transparent but visible blush of epoxy across the joint and the line will not telegraph. Oversanding and lower class glue are the causes of visible joints under paint. Cheers

[Bill Adamsen]

For painted finishes, I have used lamellos and aliphatic glue and surprisingly the seam is not visible after painting and holds up over the years. I'd think dominos/lamellos with epoxy might be a good solution for a clear finish. Alternatively, consider solid wood which is readily available in those lengths though wood require considerations for cross grain expansion/contraction.

[Greg Bieg]

Thanks guys, a lot of good suggestions.

I had read before about using an epoxy glue and carefully sanding the joint to leave almost a small subtle bead of glue showing.

I may run some random tests on some scrap pieces I have lying around. I had batted around the idea of a good glue job with biscuits for guide and alignment and then a few pocket screws underneath to hold while glue dries.

Although this might be a good excuse to tell my wife I am buying a festool joiner. Hahaha.

[Bill Dufour]

I think the glue line showing has to do with water in the glue swelling the wood. You really should wait about one year after glueup to sand the joint flat. If you sand before it has completely equalized the wood will shrink down as it dries.
I think the lack of water is the reason epoxy works well. Not that epoxy is really any better as a glue then standard water based wood glue.
Bill D

[James Biddle]

How about using a strip of hardwood between them set just above the plywood and painting/staining it a contrasting color to make it a design feature? You could also cap the ends this way.

[Wayne Lomman]

I think the glue line showing has to do with water in the glue swelling the wood. You really should wait about one year after glueup to sand the joint flat. If you sand before it has completely equalized the wood will shrink down as it dries.
I think the lack of water is the reason epoxy works well. Not that epoxy is really any better as a glue then standard water based wood glue.
Bill D

Most standard wood glues react with finishes which is why they show a line. Epoxy and resorcinol do not react so don't show a line. Cheers

[Rick Alexander]

Thanks guys, a lot of good suggestions.

I had read before about using an epoxy glue and carefully sanding the joint to leave almost a small subtle bead of glue showing.

I may run some random tests on some scrap pieces I have lying around. I had batted around the idea of a good glue job with biscuits for guide and alignment and then a few pocket screws underneath to hold while glue dries.

Although this might be a good excuse to tell my wife I am buying a festool joiner. Hahaha.

Unfortunately you will need the DF700 XL to use their fasteners and for what that thing plus the fasteners costs it's best to keep it on the down-low. Better to get forgiveness than permission on that beast for sure. I got mine last year and she still doesn't know how much I paid. Unfortunately come tax time she's gunna have a tizzy - and it's gunna cost me at the jewelry store - again. On the upside - well worth the investment.

[Curt Harms]

Thanks guys, a lot of good suggestions.

I had read before about using an epoxy glue and carefully sanding the joint to leave almost a small subtle bead of glue showing.

I may run some random tests on some scrap pieces I have lying around. I had batted around the idea of a good glue job with biscuits for guide and alignment and then a few pocket screws underneath to hold while glue dries.

Although this might be a good excuse to tell my wife I am buying a festool joiner. Hahaha.

I wonder if a router and slot cutting bit with spline would serve to reinforce the joint. Feathering epoxy sort of like drywall joint compound is an interesting idea.

[andy bessette]

Biscuits or spline and Formica.

[johnny means]

First join the boards like your Momma's life depended on it. Doesn't matter how as long as you know they will absolutely never move in relation to each other. Next take a grinder or an aggresive sander like a Rotex and grind a 1/4" trough down the seam. Go about 3" wide on either side. You want the sides to slope as gently as possible. Fill the void with Bondo, filling slightly above the surface. Sand flush with a block sander that spans the void. This works particularly well with MDF or maple ply as they paint up to a smooth finish. Personally, i reserve this level of hardship for top end commercial exhibits with huge budgets, kids playrooms get a glueline.

[Gene Takae]

I suggest using MDO. Waterproof and excellent for painting but will need to order from a plywood supplier

[Mike Cutler]

First join the boards like your Momma's life depended on it. Doesn't matter how as long as you know they will absolutely never move in relation to each other. Next take a grinder or an aggresive sander like a Rotex and grind a 1/4" trough down the seam. Go about 3" wide on either side. You want the sides to slope as gently as possible. Fill the void with Bondo, filling slightly above the surface. Sand flush with a block sander that spans the void. This works particularly well with MDF or maple ply as they paint up to a smooth finish. Personally, i reserve this level of hardship for top end commercial exhibits with huge budgets, kids playrooms get a glueline.


This is the way I would do it also. Although I might not feather it in as much for a kids playroom counter top. Good practice though.
If you have a router, buy a finger joint bit to make the edge joints. Slam them together, and you have more than enough glue surface area.
Of course, you can always use the project as an opportunity to invest in a Domino if you'd like.;),:D

[Al Launier]

The question I have, considering the difficulty in getting whatever material you want for such a long counter top, is do you really need to make it 13' long? If you could design it for a 12' length that would solve your seam problem as there are a host of materials obtainable in 12' lengths. Without knowing of your design intent, would shortening it 6" on either end, or simply an open section in the center be acceptable?
It seems like this is an example of where one should design around available materials rather than the other way around.