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Discussion Starter · #1 ·
what do you guys use to seal the seam in laminate counter tops? The horizontal seams where sheets come together are what I am concerned about...even the 45 degree cuts where joining off the shelf mitered postformed tops.
 

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what do you guys use to seal the seam in laminate counter tops? The horizontal seams where sheets come together are what I am concerned about...even the 45 degree cuts where joining off the shelf mitered postformed tops.
I have built many laminate tops and I never sealed the seam. A good double cut with the router and I never had a problem.

I am curious to hear what others do.

Dave
 

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It's been a while since I worked with laminate, but I do the same as Dave. I built a jig that will cut both pieces at the same time for a perfect fit. I think the biggest concern is where those seams are placed, i.e. near the sink :no:

The contact cement will seal the substrate to a degree, but repeated exposure to moisture will eventually cause problems.
 

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Discussion Starter · #5 ·
good point on seam placement. I'm switching to using ply for the base material after redoing my countertop made of plywood and seeing how good the condition was at the seams. I've installed postformed miters and the supplied glue (w/ bolts) indicates it keeps out water...not sure how that would work at the to of the seam unless perfect.

would you mind posting a picture of your jig?
 

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It's about 19" by 40". The second pic is a bit blurry, but it shows a rubber washer there for gripping the pieces. The dado in the center is lined with laminate so the bearing has a smooth surface to ride along. You butt the two pieces together and line them up (purpose of the black lines) and rout both pieces at once riding tight to one side of the dado or the other. As you may know, this isn't for postformed work.

I haven't done any postformed work, but I don't see why you couldn't run a bead of silicone at the top of the joint and glue the rest before clamping. It would be better than nothing.
 

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good point on seam placement. I'm switching to using ply for the base material after redoing my countertop made of plywood and seeing how good the condition was at the seams. I've installed postformed miters and the supplied glue (w/ bolts) indicates it keeps out water...not sure how that would work at the to of the seam unless perfect.

would you mind posting a picture of your jig?
I never liked using plywood for laminate work. I find it moves to much. Have had much better luck with HDPB
 

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Sorry, I can't take complete credit for it. It was a seaming jig that I first saw in Herrick Kimball's "Making Plastic-Laminate Countertops." I can only take credit for the fabrication using my carpentry skills to build it. But, it is a great jig and has served my purposes well.

And, there are many countertops that need a sheet larger than 5x12, so seams are unfortunately necessary.
 

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I have been building custom laminate tops for more then 35 years ( can't stand post form tops ) and when it comes to seams the smaller the better as far as I'm concerned. Everyone on here seems to think there is something wrong with the seam in the sink area but I have never had any problem with them. In fact I just recently changed out a counter top I did almost twenty years ago with a seam in the sink area and there was no de- lamination or any core swelling ( MDF core ) by putting the seam in the sink area the seam was reduced to less then four inches in total rather then the 25 1/2 inch of a standard top.
How my business is in northern BC Canada where we have humidity go from very high to almost nil, this can open up a seam a bit but not enough to get a finger nail in and I have still not seen any problems. This may be because of the fact I use latex contact and MDF for the core and not ten bond ( solvent base ) and particle board.
I have done some over the years with a plywood core at a customers request and not seen any difference in seam movement. I prefer not to use plywood anymore because most of the counter tops I do now are laminate bevel edge and there are far to many voids in the plywood nowadays.
Here are a few tips when doing seams.
The best way to do the seam is with both sides being routed at the same time as someone else mentioned.
Do not use the first half inch of the sheet of laminate for the seam ( finish and thickness are not consistent )
Make sure you use laminate in the same direction that it was made in the factory on both sides of the seam. If you look closely at both pieces of laminate your going to join and then rotate one of them you should be able spot when the shine match.
Do not forget to clean the contact cement off both edges before sticking them. This will make for a very tight fit.
Roll both sides toward the seam.
 

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I install a lot of laminate countertops, and any time I have a "field joint" I use a two part color matching epoxy. I'll have to get the name, but it comes in two tubes attached together and after the ends are cut, it squeezes out together. Mix with a puddy knife and while its still wet, it can be cleaned with a wet rag. I also use biscuits which really helps line up the two surfaces. Put a nice amount on both edges of the joint and use through bolts to clamp together. Wipe up excess with a wet rag. You can tweek the two surfaces with a rubber mallet. No need for seam fill when your done. By the way, this is far easier with two people. One under top wrenching bolts (usually in an awkward small cabinet) and one up top watching the seem.
Hope this helps.
 
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