Granite Counter Install By Novice

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Old 10-13-08, 08:57 PM
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Granite Counter Install By Novice

I'm having 2 cm granite kitchen counter tops fabricated to the point of being "install-ready." One is an L shape with a significant portion that will be supported in an uncommon manner. The other is straight with a undermount sink. No professional installation because I am taking it from a metro area to a remote location in British Columbia, where such trades are scarce and VERY expensive. I've thought a lot of this out and gained a great deal of knowledge through resources such as this forum. I think I'm down to details, but I'll provide an overview in case somebody notices a fatal flaw.

The L shaped piece abuts a stove and two walls, leaving three other sides with a full bullnose edge (laminate to 4 cm at edge). If you can envision the horizontal element of a capital L, that portion is supported mostly by a cabinet and is about 25x48. The vertical portion of the L is about 25x68. Where the cabinet doesn't lend support, the wall-adjoining sides will ride on lumber rails (2x2 or 2x4, haven't deciced) lag bolted into the log wall (I am cognizant about log settling, expansion, etc, - it's a 41 year old manufactured tongue/grove cedar - settling is done and I'm not worried about humidity/tempature induced changes). The long part of the L has about a 43" run from the cabinet area to it's end. This open portion makes a small dining area. Along that 43" the only natural support is on the wall side. The granite's weight should be about 260 lbs., obviously a lot of which will be distrubuted to the cabinet and wall attchments. A metal shop is making three gussetted 90 degree support brackets out of .095 wall 1 x 1/2 steel. I'll tie them to the wall with 1/4 inch lag screws. The brackets will be placed about 10" apart, with a setback from the end for asthetics. They extend 18" into the counter's 25" width. I plan a 5/8 plywood substrate. The brackets will screw to the substrate bottom as well. The straight counter is about 113 x 25. It should weigh about 320 lbs. including an 18 gauge stainless undermount sink. The sink will be cradled by a size-matched cut out in the substrate, so that it's flanges are sandwiched between the plywood and granite. A full cabinet supports the counter over its length. Also has a full bullnose on front. Both the L and straight counters have full backsplash on the wall sides.

So finally to the questions: 1) Does my unconventional support scheme sound strong enough? 2) Should I use screws, or construction adhesive between the cabinets/lumber support rails and substrate? 3) Could I use MDF instead of plywood under the granite? 5/8 is preferred for a number of reasons, and believe it or not, my Lowe's and Home Depot have no ply in 5/8. It seems the MDF flexes less and is perfectly flat, as opposed to the 1/2 ply I would have to default to. I'm not sure about screwing into MDF. 4) Construction adhesive or silicone between the granite and substrate? Most suggestions seem to be for the adhesive, but I think (god forbid!) "what if I ever need to replace the sink?" 5) Subject to what the opinion is on the last question, should I run a big bead of silicone between the sink flange and the substrate, and the flange and the granite?

Sorry to be so long winded! Thanks for any insight you may have.
 
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Old 10-14-08, 03:59 AM
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I have done a lot of kitchens, but granite is one I leave to the experts. 1. there is no such thing as "ready to install". There are always some things that are slightly different from what the template showed, and require shimming/trimming. 2. Undermount sinks are install on site, not before the fact. 3. I have never seen an underlayment used with granite. 4. The cabinets MUST be dead nuts level or it will crack. 5. The top in the area of the sink cutout must be supported while transporting, and careful handling is needed to prevent it from cracking in this weak area. 6. The only thing I have ever seen that holds the top down, is silicone dabbed around the cabinet tops, and gravity. 7. this will take a few people to help that know how to manuver this chunk of stone into place, carefully. Do you have that help??

You said 2MM(about 3/4) thick, does it have a built up edge??
 
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Old 10-14-08, 06:03 AM
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I agree with Just Bill, specially regarding the levels' issue
However, I'd like to add a note about the thickness of the counter--> it is 2cm= 0.79 inches (approx 13/16")
 
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Old 10-14-08, 07:57 AM
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Thanks for the reply Bill & PMGCA. I think having an existing formica counter is a benefit for fitting - it's not new cabinets. I plan to pay close attention to getting it level. The fabricators will reinforce several areas with 1/4 imbedded steel strips (in particular the sink cut out). Yes, the edge is built up double thickness with a full bullnose. Hence a slight "hide" of the 5/8 underlay with the 3/4 overhang. Probably four guys to set the tops. Any thoughts on the MDF vs. ply?
 
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Old 10-14-08, 09:03 AM
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MDF is just partical board pressed a little denser than high density particalboard. It will soak up moisture like a sponge and expand. It's also not as strong as plywood for supporting overhangs. I think I would opt for 3/4" substrate if you are going for full substrate. Normally none is needed. Granite is usually set directly on cabinet tops and siliconed after placement. Don't put silicone where you can't cut it with a knive. This means running a bead around the inside top of cabinets after setting the granite. It doesn't take much. The weight alone will keep it from moving. Another thought: 1" overhang is not enough with full bullnose. It will look skimpy. Use at least 1 1/2" in front of the cabinet face. Don't silicone the sink to the substrate: you may need to reposition it slightly after setting the granite. Then run a bead around between the sink and countertop. Use denatured alcohol for cleanup. That's all thats needed to seal it and hold it in place. Be sure to haul the tops vertical or they'll be a jigsaw puzzle when you get there. Handle very carefully--you wouldn't believe how delicate granite can be. Personally, I think engineered stone would be a better choice, but that's just me. Good luck
 
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Old 10-14-08, 06:37 PM
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The biggest problem here is that this countertop will be yours once you pick it up. The very real chance of breakage means you would just eat the entire cost, plus add in the pain of having to get several people to help move it (I don't think there's anyone I like enough to move a granite countertop for). Plus the fact that you will almost certainly need to trim something and won't have the tools.

Unless the cost of a local install is 3 times greater I think this is a loosing proposition. Just my opinion. I wish you luck. You're gonna need it.
 
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Old 10-19-08, 10:02 AM
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Cautions duely noted!

Thanks everbody for the responses. You guys are shaking my confidence! The overidding message seems to be let a pro handle it. Of course I am nervous about the possibility of breakage. Yes, it's my risk now. But we're talking about a $1800 job versus $5000 or probably much more; it simply would not happen without the DIY approach. I don't mean to trivialize anybody's cautions by saying "its not rocket science," but I feel that in many endevours nobody is as careful as the owner. I measured five times and cut once (well, the stone fab guys did the cuts). Any minor trimming will come out of my home's logs, but that's not anticipated.

I guess its no surprise that some of the best advice came from the username CNTRTOP. Especially leaving the sink free in the substrate for adjustment once the counter is down. The tips are truely appreciated.

BTW, it seems throughout the Desert SW 2 cm granite is ALWAYS installed on a substrate. 3 cm is common in higher-end homes, and no substrate is used.

Finally, caleyg said "I don't think there's anyone I like enough to move a granite countertop for." Sir, you need friends with better beer and tastier steaks!

Again, many thanks to all. Wish me luck
 
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Old 12-02-08, 08:42 AM
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So how did it go?

Just curious to know how the installation went...
 
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