All set to go, have a few questions

[Jon Anderson]

So I've got my prefabricated granite  (absolute black),  poly resin and coloring for the seams, shims, clamps, some suction cups & turnbuckles, denatured alcohol, and Mark's glues/seams video.  Now I've got a few questions before I begin. =)

First, I've got an undermount sink.  The slabs are layed out like this:

For the sink seams, the fore and aft portion are supported underneath, but it's not much.  In the front portion, it's basically only about 1" width of plywood, because the sink sit rather forward in the cabinet.  Is that enough support for poly resin, or should I use epoxy for those shorter seams?  I'm a bit worried because the sink seems (pun intended) like it would be a place where people might lean, etc.

Also, for the sink installation, I was planning on setting and seaming the granite in place on the countertop, and then use silicon to glue the sink on after everything has set, clamping it in place with 2x4s above and below, connected with threaded rod through the drain holes to tighten and clamp it up.  Once in place, I was going to use wood blocks and epoxy to support the edges underneath.  Does that sound like it would work?  It's 2cm granite, and I _know_ that if I try to drill holes for anchors, I'll drill right through it. =)  And there isn't much room in the sink base to work.

This past weekend, I practiced a few seams with some scrap granite pieces and miscellaneous sample pieces I had laying around.  Even on my best try, I could still feel the seam with my fingers, although it looks pretty flat (reflections match up, and a razor on edge across it shows just the faintest hair of light).  Is that reality, or should I keep practicing?  I don't think I've ever seen a professionally installed granite countertop, so I'm not sure if my expectations are unrealistic.  And this part is especially important, because my wife watched the video with me, and thinks it looks pretty easy to do.  So if I screw it up now, well....=)

And finally, when you are installing multiple pieces like this, is it best to do the seams one at a time, and let them set before moving on, or try to get them all done in one shot?  I'm going to dry fit everything first, so I hopefully won't have to adjust much.

Thanks for you help!
Jon

[Mark D.]

Jon,
regarding the sink where you say "1" worth of plywood", do you mean that the plywood only extends 1" under the edge of the piece of granite in front of the sink?

For the sink installation your technique is fully acceptable. You can use the wood blocks underneath or you can use a support bracket that screws to the cabinet and supports the sink from underneath. Here is what they look like:
http://www.defusco.com/Prep-Tools-Undermount-Sink-Bracket-Kit/c89_714/index.html

As far as your seam practice, what do you mean when you say "a razor on edge across it shows just the faintest hair of light"?
Remember that you will always see the seams and fills but done correctly they should blend and look like they were designed to be there.

You should do a seam at a time. Maybe 2 if you feel comfortable with the project. While a professional installer may do multiple seams at a time since you are new to this you should go slow.

Get back to me about the first and third issue.

Mark

[Jon Anderson]

regarding the sink where you say "1" worth of plywood", do you mean that the plywood only extends 1" under the edge of the piece of granite in front of the sink?

This is a side view of it:


Basically, the sink basin sits almost flush with the front inside of the cabinet.  So the only support for the middle piece of of granite is about the width of the cabinet frame.   It does run the hole length of the granite piece, though

As far as your seam practice, what do you mean when you say "a razor on edge across it shows just the faintest hair of light"?
Remember that you will always see the seams and fills but done correctly they should blend and look like they were designed to be there.

The seam feels about the same as the edge of a piece of paper laying on a desk.  One side of the granite is just ever so slightly higher.  When I use a razor blade as a straight edge across it, you can see a sliver of light under neath the edge.  I took a little bit too much off on the lower side trying to clean up the seam a bit, I guess.

Jon

[Mark D.]

I think you should use epoxy on this seam as it is a permanent glue and polyester resin is not. I would hate for it to come apart and fall on the floor and break somewhere down the road. Any of you fabricators have any other thoughts on this project?

As far as the seam you need to make sure you start with the top of both pieces of granite on the same plane. If you are hitting a wall going from one piece to the next they were not level to begin with. Try shimming them when you dry fit them with something that won't compress. If they are that close get a deck of plastic playing cards and shim with those.

Glad to be of service,
Mark

[scottinphoenix]

That inch of plywood in the front is normal for some sinks, especially bigger ones because they have to cut out the sink more towards the front to leave room for the faucet holes in the back. Now on those seams you probably want to cut some "bisquits" into them, basically same idea as on cabinetry but the epoxy acts as the actuall "Bisquit". (it's basically making some quarter inch cuts into the seam where the seam touches this way when you pack glue in there it has more to hold on to. Some people use metal washers and stick them in there but that gets more complicated when it comes time to glue the seam.

[Jon Anderson]

you probably want to cut some "bisquits" into them,

Any suggestions on how to cut the bisquits?  Would something like on of those mini diamond blades for a  dremel work?

[scottinphoenix]

It might work, I usually just use my makita grinder with a 5" blade on it to just make some shallow cuts, they don't have to be super deep unless your going to shove some washers in there but I never do. To add extra support I often use the bisquit method and also put caulk with the glue underneath the "rails" (the pieces of granite going across the sink) this way in a few years if the glue underneath the rails ever becomes brittle, then the caulking will still hold strong.