Replies

1. 
   DaveRicheson | Jun 30, 2008 12:56pm | #1

   Not enough information.

   A light weight concrete product can be poured over a wood framed and decked floor, but the normal thickness is 1 1/2" to 2". ( I'm having a senior moment here and can't think of what it is called). Normally this is planned for durring the intial construction and the whole plan is calculated for the additional loads.

   3/4" is pretty thin and likely to crack from deflection and seasonal movement of the framing. We need to know the joist size, spacing, and spans to even think about answering your question.

1. 
   jackwater | Jun 30, 2008 01:07pm | #2

   joists are 2x8, 16 o.c. with a 12' span. I only plan on pouring over 1/2 of the floor. It will be in a kitchen with counters and an island. I was going to put the floor under both counters and island, but I could raise the counters and island and just pour around them, if that would minimize the need for additional framing. The joists are over a pretty tight crawl space.

1. 
   FNbenthayer | Jun 30, 2008 01:39pm | #3

   You are going to have to beef up the floor framing...Thank you for using the John Bridge Forums Deflect-O-Lator :-)For joists that are SYP or Douglas Fir, in good condition, 7.25 inches tall, 1.5 inches wide, 16 inches on center, and 12 feet long between supports, the deflection calculated is 0.478 inches.This translates to a deflection of L / 302.Since the maximum deflection for tile is L / 360, and for natural stone is L / 720, your floor is rated for Sheet Vinyl or wood.

   The awful thing is that beauty is mysterious as well as terrible. God and the devil are fighting there, and the battlefield is the heart of man.
   - Fyodor Dostoyevski

   Edited 6/30/2008 6:41 am ET by FNbenthayer

2. 
   Danno | Jun 30, 2008 03:36pm | #4

   What FNBenthayer said sounds right. When reading your post, my first thought was that such a thin coating of concrete could be a problem. If you could get it thicker and get some steel reinforcement into it, and fibers, that would be good (I am not a concrete guy (maybe my head) so I'm not really giving you advice, more expressing an opinion).

   I also thought this: "Why couldn't he put down something like Durock that is in fiberglass reinforced sheets?" Seems like that would be less likely to crack, but what do you do to hide all the joints? Maybe lay it in a pattern or something and even leave space and grout (maybe with epoxy grout?) the joints? Maybe acid etch/dye the sheets of cement board? Just ideas.

    

3. 
   peteshlagor | Jul 01, 2008 05:10am | #5

   Note how I laid down the flexible concrete decking in this thread:

   http://forums.taunton.com/tp-breaktime/messages?msg=91581.1

    

1. 
   jackwater | Jul 01, 2008 12:49pm | #6

   what about concrete overlays, like colormaker.

   I was going to put durock down and skim coat over it. I had someone give me an estimate for concrete flooring before and he was going to do something along that line. I dont know exactly which product he was going to use, but it must have been some overlay material.

   any thoughts on this?

1. 
   frammer52 | Jul 01, 2008 06:03pm | #7

   Why not use gypcrete?

1. 
   DaveRicheson | Jul 01, 2008 11:25pm | #9

   gypcrete?

   That the stuff I was trying to describe. We use to build apartments that had gypcrete poured over the wood subfloors. Never saw it poured less than 1 1/4 to 1 1/2" though. It was more a sound proofing thing than anything in the second floor units.

   Don't know how it would work at 3/4" and, I'm guessing, smooth finish. What we had pumped in was just floated out, then covered with carpet.

1. 
   frammer52 | Jul 01, 2008 11:48pm | #11

   I don't know how it would work at that thickness, but it would eliminate the need for the cement board, allowing it to be poured in deeper amounts.  Works great under tile!

2. 
   jackwater | Jul 02, 2008 02:02pm | #12

   "Colormaker", as do others, makes a concrete overlay system. I think it's an epoxy cement mix. It gets applied in a thin 1/8" thick coat and can be colored and I think acid washed. It is made to be applied over older concrete as a finish. I think something like this is what a concrete guy was going to use. I dont think I would use the lath, but I dont know, and I dont know if this would work over durock- although at least it wouldnt be as bad as concrete to take out (although not a good way to go into a project- thinking how to remove it- is it?)thanks

2. 
   BillHartmann | Jul 01, 2008 06:31pm | #8

   About 2-3 years ago there was an article about puting down 1/2 - 3/4" concrete overlays on wood floors (and others) and then stamping or acid staining them.I am thinking that it was in JLC, but might have been in FHB..
   .
   A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

4. 
   popawheelie | Jul 01, 2008 11:34pm | #10

   Alot of people are just gluing down large tile. I'm not saying it's right. But it is happening alot. I suppose the grout lines break out eventually.