Installing seamed countertops

      Fitting p-lam countertops in the field, due to size and shape. September 23, 2003

How do people deal with PLAM countertops that have to be installed in two pieces due to the size? Commonly I'll have an "L" countertop and have to fit the two legs together in the field. I haven't really got a system for this that I like.

Forum Responses
(Laminate and Solid Surface Forum)
When I join two sections together in the field, I usually screw and glue about an 8 inch splice block of 3/4 particleboard under the seam. It holds pretty well and levels up the joint pretty good too. Most of my large tops are laminated in the field after the top is put on, so only the laminate joint has to be real good. If you're talking about joining tops that are already laminated, you can put cleats on both sides of the joint, leaving gaps in the cleat so that you can put draw bolts or "dog bones" in to clamp the joint tight.

From contributor R:
When I join decks in the field, I use a 1/4 spline. I leave one old router set up all the time with a spline bit. A biscuit jointer works well too. I never actually join tops together that are already laminated. I'll make a long section or do it on site. The preparation to make a decent joint and putting it together will easily negate any savings in time, plus the joint will be second rate.

From contributor V:
I often make up countertops that are large L-shaped or U-shaped and require a field seam. I fabricate the tops in the shop and make up the seamed joints as follows: The flakeboard is cut to size on a vertical panel saw. Edge build-ups are installed if it is a self edge top. The areas to be seamed are laminated on each edge with V32 laminate and trimmed. I then cut biscuit slots on 6" centers along the seamed joint on each side. I then install a 3/4" flakeboard cleat that overlaps the seam approximately 8" on each side, on the underside of one of the pieces to be jointed and glue and staple in place. I then dry fit no. 20 biscuits in place and assemble the top and clamp it tight (seam area). From the underside I pre-drill and countersink and screw the cleat to the other top with two rows of 1 1/4" coarse thread screws, usually 8 to 10 depending on the depth of the top. Then belt sand the seam area on top to make sure it is level and smooth. Remove the screws and disassemble the tops. Then laminate the self edges and countertop deck as usual. When trimming the seamed edge I use a bearing piloted laminate trimming bit to get a smooth cut. The V32 edge will trim smoother than trimming with the bearing against the flakeboard. When cutting the flakeboard for the seamed area, it is important that the seam fit tight prior to laminating with V32. I will clean up the glue after trimming the seam with reducer, but will leave the laminate a little long. The tops can then be dry fitted together in the shop and if necessary, the seam can be worked with a laminate file on edge or block plane.

I have made up countertops over 40' long in this manner and then fit them together on the job site and have gotten a good seam. Finally, after the countertop is installed on site, I like to fill the seam with Kampel SeamFil. This puts the finishing touch on the seam. A lot of times, I have a tough time finding the seam after it has been filled properly, and I know where it is.

From contributor R:
That's a similar method to what I've done in the past on commercial work that was impossible to do on site. It works reasonably well. The joints are never quite as good as if you staggered substrate and laminate, though. But as a laminate man versus someone who does laminate part time, with the extra work in preparation of the tops, the shop space required, and the potential for shipping damage, I find it easier to do on site unless it's a small top with no joints.

From contributor V:
Whenever possible, I make up tops to eliminate any seams. I agree that the staggered seams are stronger, but on most of the jobs I do, it is not possible to laminate the tops on site. I also use spray contact adhesive and on the job site the odor and flammability are an issue. Most of the tops I do with a field seam are tops that are too large to safely transport or are too large to move into the installation area of the job site in one piece. This is especially true of large U-shaped tops. I just completed (2) L-shaped tops that each required field seams because they are being shipped to MA, about six hours away from my shop. Using the method I indicated in my post, I was able to get very tight hairline seams on both of the tops.

I think contibutor V's method is a lot of overkill, and the use of Seamfill is for an average/bad seam. You should never have to use Seamfill with a good seam. I like to rout both pieces of laminate together so I get a mirror image seam, and never need seam fill.

From contributor V:
I also will mirror image rout the laminate when doing a staggered seam, but I was referring to tops shipped as two separate pieces already laminated and then assembled on site. Are you mirror image routing the laminate, substrate and build up after the tops have been completed?

From contributor S:
I will join a two-piece top together before laminating, and after laminating pull tops apart and protect seams for shipping.

From contributor P:
I agree, the best way to get a perfect field seam, with no Seamfil, is to have the top built in a shop that builds the top complete, does a mirror cut on the top, and then puts mitre bolt hole in the top for the installer. The tops are then test fitted together to make sure the fit is correct. The ends are protected, crated and shipped. We have had great luck building tops this way. And it is a lot easier for the installer to unwrap the top, scribe, and install.

From contributor R:
A perfect miter has the laminate staggered from the substrate at least 6" - that way any movement of the substrate is not telegraphed through to the laminate. To make my joints I have a straight edge of MDF I clamp on to the laminate. I use a router with a 1.25" top bearing trim bit to trim laminate. This works really well with very little filing. The joints end up invisible from a few feet away and they stay that way.

From the original questioner:
Just to help me understand... you build the tops, bolt the pieces together before laminating. Then laminate, lining the laminate seam up with the substrate seam. Then take it apart. Is that how it works?

From contributor S:
I usually try to get a 2mm lip on one side, and join the top together in the field with loads of yellow glue and a small bead of silicone along the top edge.

All this makes me wonder if it's really worth the effort? Is the reward worth it to the fabricator? Is the benefit worth anything extra for the client? If they ordered from a high end office furniture manufacturer, wouldn't they be perfectly pleased with well executed butt joints?

From contributor R:
I figure out where my laminate joints are going to be and build my decks so the joints in the deck and laminate don't line up, then I install the decks on site, then laminate them. It's just as quick to do the laminate on site as to do it in the shop. Probably less if you figure prep time for the joint and the extra care involved with shipping large finished decks and the subsequent scribing and the inevitable replacement of screwed up counters. This of course relies on the job not being halfway across the country with the boss unwilling to spring for travel time for a counterguy.

From contributor C:
I'm with you, contributor P. We laminate 'em, cut 'em, route the bolt holes, cardboard 'em, and ship 'em. Are the rest of you guys making tops for a living or just a few tops to go along with your cabinets?

From the original questioner:
Contributor C, sounds like you've got a system that works. Do you build the countertop slightly oversized, and do a mirror cut on it at the break? How do you do the mirror cut? Where do you typically seam the counter?

From contributor C:
Yes, the top will have to be slightly oversized. Mirror cut? We cut both edges on either a Midwest beam saw or an EdgeTech beam saw. The EdgeTech works great for "square" miters, standard butt joints, etc. If you need an out of square miter, the old Midwest can't be beat. "Where" is really dictated by the top, cabinets (if any), sink(s), material sizes, whether the top is postformed or selfedge, etc.

I can't believe that in this entire thread, only one person mentions dog bones, butterfly fasteners, Tite-joint fasteners, miter bolts, whatever you want to call them and glue.

From contributor R:
I assumed we were talking about flatlay for commercial work, etc, but what we were really talking about is making butt joints in covetop. My apologies. I'm a flatlay installer and I do not get involved in cove top at all. My last thoughts on this… I have found in 23 years experience that it's easier to do flatlay on site, conditions permitting. I can do two large homes in a day and I don't have to worry about walls out of square, etc. but you guys are right - if it's a situation where the counters are really simple or smell, dust, noise are an issue.

From the original questioner:
I do primarily build cabinets, though I have done quite a few countertops to go along with them. Typically I have built the larger ones in place but clearly this is inefficient, which is why I wrote the original post.

From contributor C:
Contributor R, it doesn't matter - flat work, PF, commercial, residential. We just finished a small school project. Two science rooms had U-shaped tops, left leg 24', center leg 45', and the right leg 27'. These were flat decks with Wilsonart Chem-Surf. You mean it's faster to lay those up in the field, than to make up the decks in the shop, cut the ends, ship them and bolt them together on the jobsite? I'm sorry, I can't buy it. When you have a shop with the equipment needed to produce tops, spray booth, pinch roller, all the various trim routers, cutout machine, beam saws, bolt hole machine, 14' ceilings, etc., I can't believe that it's faster to produce them in the field. I have no idea how many kitchens we produce in a given day. If we're using two as the yardstick, I'd be willing check our production for the next week, go through the orders, and see how many kitchens there are, divide by the employees and let you know.

I don't care whether you build a top a year, or 20 a day. It is the fastest, easiest, most efficient way to put two pieces of countertops together. It doesn't require any clamps, it's gives you some flexibility as far as aligning your joint, and in the end, all your doing is using the bolts to hold the joint together and in place until the glue dries. And we're talking about joining two pieces of countertop, not two pieces of substrate.

From the original questioner:
Contributor C, your method does seem valid. I have used drawbolts in the past and they do work well, as this is what they are made for. Though I do have plenty of equipment, I don't have a beam saw, and am trying to find a way to cut the countertops so that I have a tight seam when tying the two pieces back together in the field.

From contributor T:
There's a big difference here, it appears, that's being overlooked. Contributor C, you look to be a pretty good sized shop, while I think the original questioner has a smaller shop, like mine (two guys). We occasionally do lami tops. I sub out my postformed stuff to a great fabricator nearby (I'm in LA). We do all our fabrication using a table saw and hand tools.

For straight tops in line we laminate the butting ends (after checking the raw substrates for fit). Same for a butted corner. I use a surface-mounted connector that draws the pieces together and has a vertical adjusting screw to fine-tune the surface.

Same thing applies if you miter into a corner, as with a wood grain pattern. I sometimes use a corbel coming at 45 degrees out of such a corner rather than drawbolts (this of course assumes it's a desk surface rather than a kitchen).

(Note: I *always* template corners before fabricating. It's much easier to prep as you go in the shop than to have to scribe a 94-degree corner in the field.)

Now I have a related question for the group, or specifically for very small shops who fabricate as I do, using only hand tools:

In building tops by hand, where the splash is a separate piece attached after laminating or even in the field, what have you found gives you the best fit of splash to top? I've tried several things, including silicone and color caulks, but haven't found anything I'm totally satisfied with. Any methods you guys use that you really like?

We are a two-man shop with limited tools as you are. We lay up the splashes oversize, rip on the table saw, and use 2" screws around 6" on center to attach to decks. Color matched caulk where the match is really good, or clear caulk the rest of the time works for us. The key seems to be a good cut on the splash edges - if you rip the splash net, laminate, then rout the laminate to the splash width, then the joints aren't going to be as good as ripping pre-laminated pieces.

From contributor T:
You're absolutely right. I've been laminating my splashes after cutting them. I can see, now that you point it out, that your method will give a better result.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor Y:
I have built cabinets for 16 years. Now I'm installing countertops everyday - solid surface, laminate, and cultured marble. The way we do a plam joint is to cut the top in a 19 in. mitersaw on whatever angle it's supposed to be. Butt the two peices together and see how well they line up. If they're good, flip them upside down and route slots for the drawbolts. Take the tops to house for installation. Slide one top up to the wall, then the other top. See how much must be scribed off the tops to make them fit tight to the wall. Drawbolt them together with resin glue in the joint. Tap the tops flush with a hammer. Easy as that.

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