[hubbard53]

I am installing 6" x 36" 'wood look' porcelain tile over 6 year old concrete basement floor. Floor is in good condition with no cracks and level so I have no concern with the condition of the substrate.

However, I am installing nearly 700 sq/ft which will cross at least one wall-to-wall expansion joint (perpendicular to direction of tile) and 2 minor (< 6 ft) expansion joints.

I know my options are either using a product like ditra (which increases my cost of project by 50%) or carry the joint through to the tile spacing. Carrying the joint through is not an option given the size, pattern, and direction of the joint through the filed of tile.

How frequently does a concrete basement floor (its a 13 course basement so the floor is well below frost line and not subject to wide fluxuations in temperatures) expand enough to break tile?

Based on experience, how high of a risk do you attribute to tiling directly over the concrete?

Ive used ditra over an exterior patio, tiling over expansion joints, with success so am experienced using that product. Are there any other products that do the same things at a lower cost?

Hypothetically, what If I apply ditra on both sides of the expansion joints only (and the rest of the tile is applied directly to concrete). Would that 1/4" difference over in the middle of a 600 sq/ft field of tile be noticed and would it affect the stability of the floor? (not saying I am going to do this but I just wonder about the feasibility)

 

[SMLWinds]

I am no expert, but my opinion would be that Ditra is the "right" answer in this scenario. I think there may be some other options, but by the time you tackle them and add their respective cost the money you are saving is not worth the benefit of using Ditra. I had a very similar situation finishing a large 2 car garage and used Ditra--it worked very well.

I don't think using Ditra over part of the floor is a good option (but again am no expert!). I think the time you spend trying to get the tile level and possibly living with an imperfect installation would again justify waiting until you have the extra capital available to use Ditra.

I feel that using Ditra is going to allow you to have a nice looking job and sleep easier at night. Plus, it would hopefully avoid future costs down the road from fixing issues that arise. I know there are probably other options and hopefully others will offer those but I think using Ditra--even if it means waiting and saving for the project--is probably the best long term solution.

 

[JazMan]

Hi Hubbard,

36" tiles require an extremely flat floor. I know you said the floor is in good condition, but have you checked that every sq. inch is flat within specs? Level is irrelevant, flat is what you need.

I know my options are either using a product like ditra......

No, wrong. Ditra does not eliminate the need to honor the joint through Ditra and into the tilework. Where did you get that, certainly not Schluter. Ditra is not a crack isolation membrane, it's an uncoupling membrane. Ditra is my favorite for floors, but it is not intended for what you wanna do.

Are there any other products that do the same things at a lower cost?

A product that will do what you want is Noble CIS. Read all the info, don't skip the CAD detail for the method you choose. http://noblecompany.com/products/nobleseal-cis/

Cheaper than Ditra? No, CIS is more than Ditra. But, you can select a method that applies CIS only to the joints/cracks. So it can be cheaper for the job. See CAD detail.

You still need the perimeter expansion space and field joints every 20-25 ft and in certain other spots depending on shape and size.

Jaz

 

[hubbard53]

thanks, JazMan. It looks as if the Noble CIS is exactly what I'm looking for. I like how it specifies partial coverage.

When I was checking my floor, I shot a laser along the surface and checked each spot where the laser was deflected to ensure the floor was not out of level or had a 'hump'.

My only area of concern is around the expansion joints where the edges are slightly imperfect. I planned to grind the edges.

Do you have another suggestion for checking for flatness? I get that 36" tile is more affected by imperfections as an imperfection beneath one end is exponentially more significant on the other end.

Thanks!

 

[JazMan]

That's right..... a hump the size of a tooth pick can look like the cat is under there on the other end. I didn't use lasers, although they're excellent for this purpose when used correctly. A good long straight edge can easily be repositioned to check every which way.

For large tiles the spec is; flat within ⅛" in any 10 ft. radius and 1/16" in 24" of the required plane. So almost as flat as your dinning room table. Measure the dif from two high spots if any.

The area at the expansion/control joint may be distorted by poor workmanship or it could be the slab has curled. Curling is very common at ends. Just make it as flat as you can and remember that the expansion joint in the tilework must be as wide as the joint or min. ¼" wide if the control joint is a saw cut. Noble's spec may be different in this regard, I don't remember if they think the grout width can be maintained. Be sure to use the caulk as they show in the CAD detail.

Jaz

 

[hubbard53]

thanks again. Speaking of the tile expansion joint, how does one do an expansion joint using long tile that it layed in an 1/3 offset pattern like hardwood?

 

[JazMan]

All depends on which product/method you're using under the tiles. If you go with CIS, just follow their directions and CAD detail.

Jaz