Replies

1. 
   Piffin | Sep 25, 2002 04:48am | #1

   If I absolutely HAD to do it I would include a mastic or adhesive. Why do you think you need it? Smooth surface for application? Bad paint on block? Dimension shimming?

   Excellence is its own reward!
2. 
   Scooter1 | Sep 25, 2002 07:14am | #2

   Why would you do it? Thinset won't stick very well to paint.

   I think I'd leave the CBU at Home Depot and shoot some 2.4 diamond lathe onto the CMU and use some wall float for a scratch coat and then set it with standard thinset.

   Any CBU would probably crumble if you used a ramset; concrete nails wouldn't hold it secure enough.

   I'd stick to mud!

   Regards,

   Boris

   "Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927

3. 
   chiefclancy | Sep 25, 2002 07:56am | #3

   The first thing you need to do is make sure the wall is free of cracks and is relatively flat. How big of an area is this? I do not think backerboard is designed to be attached to anything other than framing - you should check with the manufacturer to make sure the backerboard you choose is compatible with this type of installation. What size tiles are you going to install?

   Concrete block actually makes a good setting base for tile provided that it's relatively flat and free of cracks. If the surface is too irregular to set tile directly on to, I would use mud for this job. First coat the block in latex modified thinset to bond the mortar to the block, then float a thin (1/2") layer of wall mud over the block to fill in the irregularities. You can use float strips temporarily nailed to the wall to help with the screeding process. However, this is really only practical if it's a small area.

4. 
   Mooney | Sep 25, 2002 02:34pm | #4

   Your going to get a buffet of information it seems . And heres some more ;

   I hung sheetrock in a motel to haydite concrete blocks with roof tacks and adhesive .  I  finished it and painted it . Since then wall vinyl has been hung. The job is 20 years old now and still has no problems as I have been there many times doing maintenence. That said ;

   First the wall would have to be free from cracks and basicly a flat wall, other wise I would lath it so the wall could be shimmed which would also provide for some movement.

   Roof tacks can be driven easily through backer board into haydite blocks. The nail is set in the board first and then a drive home with a roof hatchet. A drywall hammer isnt balanced , nor heavy enough . Dont even think about a carpenter hammer of any sort. Since that job , Ive done several using this method. Its not a problem , really.  The nails will also be coated with the adhesive as they are driven , so liberal amounts of adhesive is used. Of course plenty of nailing would be good sense .

   This would be the cheapest and fastest way I know .

   Tim Mooney

1. 
   Jim7W9 | Sep 25, 2002 03:00pm | #5

   The wall is very sound, no cracks, and good an flat. This is in a new school, less than a year old. They want to put up a tile mosiac of an American Flag. Size is approx 9ft x 7ft.  I did a similar project about 11 years ago at another school where we installed 3/4" plywood first and then fastened the backerboard to that, finishing off with a wood frame around the entire mosaic. It's still up and looks good. I'm only supplying the base for the tile, students all contribute to doing the actual tile install.

   Jim

1. 
   Mooney | Sep 25, 2002 03:18pm | #6

   I dont see a problem doing what I reccomended , but if you have money available , you could also do what you mentioned too.

   Tim Mooney

2. 
   Mooney | Sep 25, 2002 06:32pm | #7

   I guess I have a question for you.

   How can you install the plywood any better than my suggestion for installing the backer board? This is a few hours later from my last post , so Ive been thinking about it. The backer board is four by four . Thats seems like enough surface area to hold as well as plywood. One thing to note here is that I stacked the rock on the floor , thus letting the floor hold it . [I know rock shouldnt be on the floor to draw moisture ] Once held by the floor , its only an issue of keeping from falling over when its already plumb. I assume the tile would be stacted from the floor also. I think IM getting deeper in this than I need to but Im trying to be sure my self . I would still nail the backer to the blocks and glue, with out any reservations. I guess to say I wouldnt mind giving warrantee if this were my job.

   Tim Mooney 

1. 
   Jim7W9 | Sep 25, 2002 07:09pm | #8

   Tim, my only concern with nailing or screwing the backer to the block is having good long term fastening so after a few years it doesn't start pulling away from the wall.

   The size of this mosaic is 9 ft w x 7 ft h and will not be sitting on the floor. We will be putting a frame around the entire mosaic that will also be fastened to the block as well as aiding in supporting the weight. i was just wondering if I would benefit myself with the plywood since I could actually use toggle bolts in the block that would insure

   it couldn't pull away from the wall. Then screw the backer to the plywood. You mention glue. What type of glue /adhesive are you refering to.

   Honestly , I'm not trying to make this job more complicated than it needs to be. I'm just trying for the most practical installation possible without being over kill.

   Jim

1. 
   Mooney | Sep 26, 2002 12:11am | #9

   I am talking pls premium construction adhesive. There is also a gallon size that can be notch trowled. If you are surrounding the peice with trim , youve got the best idea. You would have to have something to attach trim to. I think your on the right track. I can visualize a cap trim incasing the 3/4 on the sides and enough of a reveal onthe face to give it a border. Sounds good to me Jim.

   Tim Mooney

2. 
   Piffin | Sep 26, 2002 12:40am | #10

   I had a leaning when I first asked. Now I know. I'm with the mud boys.

   build the frame with wood and apply it with PL Premium. Tape it off and use for a screed. Or just do the backer board for a frame now to use as screed and nail trim to it later. Put wire lathe on the wall and mud coat. Then let the kiddos fly the flag with mastic. This will stand the kind of abuse that kids will give it in the next twenty years.Excellence is its own reward!

3. 
   Jim7W9 | Sep 26, 2002 01:54am | #11

   Thanks for all your thoughts Tim. What your visualizing is exactly what I was thinking of doing. Once again, many thanks from a first time( but certainly not last time) user of this site.

   Jim

4. 
   Mooney | Sep 26, 2002 04:47am | #12

   Come back and join us Jim . We are kinda addicted . LOL.

   Tim Mooney

5. 
   Jim7W9 | Sep 26, 2002 02:29pm | #13

   OK, I've also be given the suggestion to grind the paint of the block and adhere the tiles right to the block. Any thoughts on this approach.

   Note: Wall was painted with block filler, and 2 coats of high gloss water borne acrylic paint. This stuff is the water based version of 2 part expoxy paint. It gets real hard.

   Jim

6. 
   Mooney | Sep 26, 2002 02:42pm | #14

   We are getting into an area of some of my expertise now . The only way thats going to happen is sand blast. I would have already mentioned it , but I know its too messy inside a school. Ive slept on this job , got up thinking about it this morning . Funny you sent this at this time . I think the plywood needs be be stacked off the floor.  I think your job is too heavy to hang on hollow concrete haydite blocks. I also think it could be made attractive. The plywood could go to the ceiling also, if you wanted to put something with it such as a scalloped top. I still think you are on the right track. But the floor needs to do 90 percent of the holding in my opinion .

   Tim Mooney

7. 
   Jim7W9 | Sep 26, 2002 03:23pm | #15

   Thanks for all the help and advice, I think we'll make a go of it.

   Jim