I'm attaching 3/4" plywood to my base cabinets. How do I connect the seams for optimum stability?

Question

I've heard that you shouldn't have seams over a dishwasher, so I am going to screw both to the nearest cabinet. But what is the correct way to do this? Do I need to bevel the edges of each plywood board to fit into eachother? Or can the factory edges just sit next to one another? I need to have a flush system, but am not sure how to reinforce the base cabinet (it's very thin and I don't know if both plywood boards will be able to be screwed in). Is there a standard way to do this? Thanks so much.

Answer 1

I am afraid, that you need to provide some details here....

Where are you placing the plywood, and why plywood? (Are you putting down a plywood base in preperation for tile work, for example?)
How many pieces?
Is the counter in a straight line, or angled?

Typical countertop mounting to cabinet bases would mean securing the top from underneath, by shooting a screw thru the corner braces of the cabinet,up into the countertop. For added strength where necessary, a small cleat can be added on one side or the other, of the cabinet wall. I would apply some glue to the cleat, and shoot screws in from the other direction (thru the cabinet wall) into the cleat. This would give a little more room and strength, to help secure the top from underneath.
Another option, is to use countertop fasteners to secure edges together. These can be found in most building supply stores, or online, at places like Rockler. Here is a sample of what I am talking about - http://www.rockler.com/product.cfm?page=10770&filter=countertop%20fastener
There are several versions of this type of fastener available. What it does, is pull the edges together...and is a very common item in commercial cabinet manufacturing. Just a note - these are installed from the Underside of the countertop material.

Another method of joining materials... take a router, and cut a groove into both edges, and then cut a piece of wood that will almost fill that groove, but not quite... This is called making a spline. Squeeze some glue (titebond works very well for this) into the grooves, insert the spline(s), and then use the 'zip bolt' to tighten them together. I say 'splines' because you do not want the spline where the zip bolt is at.
If you have a 'biscuit joiner' on hand, then that can be used instead of the router -- simply pop some biscuit joints at several places along the edges, glue, and insert the biscuits. (Biscuit joints can be cut with the special cutter, or router, with the appropriate router bit)
While at Rockler, just do a search on "Biscuit", and you will see several items pop up.

And of course, there is always the dowel :)

Let me know a little more about what you are attempting to do, be glad to help :)

Good Luck

Answer 2

Let's start from the top. Why are there seams over your dishwasher? Do you have it under the counter? All I can say is, it has to be level and the newer dishwashers have levelers on the feet. Why are you attaching 3/4 inch plywood to your base cabinets? It will be difficult to find screws that will hold plywood and the cabinet-better ask them at the local hardware store. I am assuming this is an older dishwasher and you don't have instructions. My husband put mine in at the end of our kitchen cabinet cuz I didn't want to lose a base cab. and then we bought a piece of counter top to span it and 3 other base cabinets, none of which are screwed to nothing. Our dishwasher is fine. I don't know about the 'no seams over a dishwasher deal'.