White thinset over grey colored fibertaped joints [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

PDA

View Full Version : White thinset over grey colored fibertaped joints


fenderskirt66
03-09-2005, 04:52 PM
Hey everyone! Brand new to tiling and new guy to the board. I searched all over for info about this, and didn't see anything so I figured I would ask. First off, installing 12x12 Autumn colored gauged slate from HD (Made in India) onto 1/4" hardibacker, 5/8's plywood subfloor with 16" joists. I used Versabond fortified grey colored thinset underneath the backerboard as well as to seal the fiber tape where the backerboard joints lie. With that being said, I have heard the "ideal" mortar to use with slate is white in color. With my grey fiber joints, will this be a problem in using the white morter to lay the tile, meaning will it be visible? I will be using a 1/4 x 3/8 x 1/4 square notched trowel to spread the thinset. 1 last thing, I read a post earlier about a guy that had slight uneven-ness where the backerboard joints came together. I too have this going on, do I need to sand the fiber taped joints, or will the thinset take care of the ever so slight difference for me?
Thanks in advance, looking forward to the feedback.

PS-
Can someone recommend a good brand from HD for thinset and sealer for this slate job?

Kelly
Fenderskirt66

Sponsored Links


Davestone
03-09-2005, 05:47 PM
Kelly, i've got bad news,the thinset is the least of your problems. First, the 5/8 ply with 1/4" hardi doesn't meet subfloor requirements of 11/8, let alone a stone requirement.Would you give us your joist unsupported span length, and joist dimensions? I'm afraid your floor will not support this stone installation. :)

fenderskirt66
03-09-2005, 06:13 PM
Hey DaveStone, thanks for the quick response. I just measured and the joists are 9" tall x 1.5" wide. The distance between the joist's at the center of the board is approx 16". The joists are about 12' long with wood cross support pieces in the middle at 6'. How am I looking?

Kelly
Fenderskirt66

Davestone
03-09-2005, 06:20 PM
I'm afraid the deflection(or flexibility) for your floor is unsuitable for stone,but would be o.k. for tile...if your subfloor was brought to 11/8" total thickness,at least,that's bare minimum.You can check above on the litle ...deflecto...for yourself. :)

fenderskirt66
03-09-2005, 06:38 PM
DaveStone-
Thanks for the info, would the fact that I have joist cross support's at 6' change the joist length to 6' in the deflecto calculator? Or would it still remain 12'? What a freakin bummer if I can't go with slate, I have it in my living room and ready to go. Please let me know what my alternatives are....I already have the 1/4 backerboard mudded and screwed.

Thanks again for you time.

Davestone
03-09-2005, 06:49 PM
By cross supports,you mean the 2x2boards in a x pattern between the trusses right? If so i'm afraid that's not enough.You would have to add some joists to your joists...sistering them,or nailing them along the side of the existing joists. Or adding a cross support of some kind under the joist at about midway.Or building a closet under the joists,or sumthin like that to shorten the span.If you did all that, i'm afraid you wouldstill need more plywood to give you the minimum.We might check Ditra to see what their minimums are, but that would be after fixing the deflection issue.Now,ya know they have a lot of porcelains that look like stone.sorry,i would hate to see you waste money on this installation the way it is now...cause it'll fail...this site is full of these stories. :)

Davestone
03-09-2005, 06:59 PM
Ditra won't help, they'll want double plywood too,for stone. :)

fenderskirt66
03-09-2005, 07:12 PM
Hey Davestone, I have pieces of the exact floor joist material (9x1.5") that run cross wise and are nailed between each floor joist, they run every 6 feet. Also, I have a few boxes of hardibacker screws left over, what if I install those every so many inches? Would that improve the strength significantly?

Thanks,
Kelly

Davestone
03-09-2005, 07:17 PM
Sorry, that's not the problem,the hardi isn't any strength,it's just a good material for the thinset to stick to.All your strength is in the joists,and they have to be within a short enough distance to stop bending and bouncing,then the plywood has to be strong enough not to bend in between the joists. :)

fenderskirt66
03-09-2005, 07:38 PM
DaveStone-
So what your saying is, even though I have cross joists every 6', that's not going to be sufficiant support. What if I cross braced the floor even more, would that make the difference? I weight almost 200 lbs and can jump up and down on the floor with no give, I was really convinced that I have a sturdy enough floor to lay the stone. The area's that I want to lay the slate are a 12x12 kitchen and a 4x8 entryway....perhaps since those areas aren't that big will that get me the green light? I don't mean to sound argumentative, just really want this slate to work out and be a lasting thing.

Thanks!

Davestone
03-09-2005, 07:41 PM
If the cross joists run under the floor joists,and not between them it'll work.But you still need more plywood.Otherwise you have to find a way to shorten the unsupported span of the joists,and you still need more plywood. :)

fenderskirt66
03-10-2005, 10:17 AM
DaveStone or anyone-
Going to attempt to post a few pics of the floor situation from the underside. I appreciate all your insight and knowledge, I just want to get it right the first time. What advice can you offer me so that I an make this slate work? Will adding additional support between the floor joists under the section where the future tile will be instaled provide the appropriate strength? Are you more worried about the weight of the slate "bowing" the floor between the joists?

Pic 1 is of the underside of my kitchen, floor joists are 16" apart with the cross section pieces 6' from the concrete slab wall and 6' from the center support beams (3 floor joists put together). There is a hydraulic floor pole in the center of the center support beams for added strength.

Pic 2 is a long shot showing the other set of cross support's and center support section.

Thanks to anyone that can provide feedback!

Kelly
fenderskirt66