Glue for Laying Up an Overhanging Wood Countertop
What kind of adhesive will work well for a wood countertop subject to some unusual structural stresses? July 9, 2007
Question
I just started making solid wood countertops for customers. One customer wants me to build a solid wood maple countertop (6' x 36" edge side up) for an island in his kitchen. It will have an 18" overhang and will be about 2" thick. I plan on gluing up the 8/4 boards with no steel rods. (Maybe biscuits for alignment purposes). Will this countertop be strong enough for the 18" overhang? (The overhang would be down the 6' side.) I'm sure the customer's kids will stand/sit on this overhang from time to time. Your suggestions are welcomed.
Forum Responses
(Adhesive Forum)
From contributor F:
I see no problem with the overhang, however, make sure the top is securely fastened to the cabinets. Your choice of glue is important.
From the original questioner:
Would there be much of a difference between Titebond II and a polyurethane glue like
Gorilla glue? I'd rather use the Titebond II glue if they have similar strengths since it is easier to work with. Or is there another glue I should consider?
From contributor F:
I'm not a glue expert but I think the
Gorilla glue would be better. Not sure though what the glue line looks like under a finish. Which, by the way, is going to be the most important factor.
From contributor G:
I can't remember the exact figures, but when I had to do a maple shear strength test to ASTM standards, to test different adhesives, modified PVA glues (such as Titebond 2) were stronger than polyurethane glues. In any rate, Titebond 2 is plenty strong enough (the fibers themselves will shear, not the glueline) for this application, and the ease of use certainly doesn't hurt.
From contributor S:
If you are concerned about strength, then go for PVA. The joint will be stronger than PU. If you want an even stronger joint, then go for a one-shot urea formaldehyde of resorcinol formaldehyde glue. They make boats, wooden gliders, etc. with that stuff, so it's really strong.
From the original questioner:
Excellent feedback! I think I will go with the Titebond II. In the past for solid wood countertops, I've used figure-8 metal fasteners on the base to hold the countertops in place and allow for wood movement. Do you think these are sufficient for an island that has an overhang? Or are there other fastening techniques that you use?
From contributor F:
I would not count on the figure 8s. Depending on what kind of room you have in the cabinet, either some well-fastened blocks to screw to or metal angle brackets.
From contributor P:
Have you used Titebond III? It is even more water resistant and the thing that I don't care for with II is that its open time is short… Too fast when laminating, and III is just as strong and the open time is longer.
From contributor J:
Titebond also makes a glue with a longer open time called Extend. Good for those time consuming glue-ups. One other thing with the Titebond family - if you have temperature issues like we do here in the northeast, their different glues have different minimum temperature ratings for use in colder conditions. If I remember right, one of them goes as low as 45 degrees.
As previously stated, any decent glue joint will be stronger than the wood, so you should be okay, and I think a 2" thick top should be strong enough to support a couple of pounds, as long as the adults don't try to sit on their countertops.
From the original questioner:
Thanks for the good advice. I definitely want to take my time with this job. I'll have to check out the extended time Titebond.
From contributor B:
Be aware that Titebond 2 is temperature sensitive. We had a failure because of this. Glue your blank and set on sawhorses and cover with a tarp, place a small heater underneath. I don't like to leave the heater unattended, but your call. If you read the label, this is spelled out. In Boise during the winter, it is not warm. Our shop is heated to 58 and that is not warm enough.
From contributor J:
If your shop is at 58 degrees, you can try leaving a shop light under your tarp. A 60 or 100 watt bulb would probably generate enough heat to raise the temperature enough for your glue to set. Much safer if you need to leave it overnight too. Check out the Titebond Extend also - I just checked and it's minimum temp is supposedly 40 degrees.
From contributor C:
Somebody know where I can buy resorcinol formaldehyde glue? I live in the New York area and I would like to make a very strong joint on hard maple end grain.
From contributor S:
You might find RF (or for that matter MF - melamine formaldehyde) more difficult to get hold of in smaller quantities as they are generally used for structural woodwork. They are also more expensive than the similar urea formaldehyde (UF) glues. UF is manufactured under the trade name Cascophen by Borden Chemical. They also manufacture RF, MF and other resin compounds. RF is exterior grade, UF is generally interior grade.
