james in florida

[james w spruill]

I have a master bath renovation nearly complete and am preparing to lay travertine stone.To prepare the subfloor ,which was an old concrete slab ,we struck a surveyor's transit line to achieve correct level and poured self leveling concrete to an average of about 1 1/8 to 1 3/4 or so inches.We mixed the self leveling material exactly by direction and the result was very satisfactory and 'slick'. It seemed like the perfect substrate for the travertine(I understand that being level with this material is critical) and we were preparing -still are - to get busy on the installation.I noticed this morning however that there were fine cracks running through a good bit of the SL concrete slab.Is this something to be concerned about? It would definitly be a problem- a disaster - if I had been planning to use the SLC as a decorative floor... but am I going to be ok using white all purpose thinset mortar for my app and just go ahead and go with it or is my travertine going to explode on me in the near future?:yikes:?
I thank some wise soul in advance for lending me thine ear and some sound council.

 

[david campbell]

would prefer to use a white flexible adhesive myself!

 

[inspiredandy]

Hi James,

Tap the floor around the cracks to see if there are any hollow spots. If there are you will need to cut out that section and do it again.
Usually, if cracks or hollow spots appear it's because the substrate has sucked the moisture out of the slc before it has had enough time to set properly. This is down to the amount of primer that was put down. I recently learnt to my cost that you must prime the substrate properly first.

Hope this helps.

 

[james w spruill]

I'm pretty sure my contractor did not use a primer of any kind for the substrate.It was quite clean and free of debris but they did not use a primer. Think we're toast ?

 

[Rob Z]

Hi James,

We use a fair amount of SLC and get good results by making sure we follow the manufacturer's instructions to the letter and also priming the surface thoroughly with at least two coats of primer that are agitated into the surface of the concrete with a brush and not just rolled on.

We also install sill seal around the perimeter to form an expansion strip, and ensure that there is no direct sunlight, air movement, excessive heat, or other factors that would dehydrate the SLC pour too quickly.

The depth that you are talking about might have possibly required the use of aggregate added to the mix, although there are some brands of SLC that can go in that deep as-is right out of the bag. Which brand did you use?

The cracks might be the type that are in the "normal" range, given the size of the pour. ham many bags went in and over what size area?

I would be concerned about the lack of primer. As Andy mentioned, tap the surface to check for hollow sounds.

Any chance you could post a photo?

 

[Rob Z]

James, I also should add....for large floors and for deep pours, we usually try to do it in two lifts rather than one, with primer applied between the two pours. This seems to work out better than going for it all in one shot.

 

[james w spruill]

Rob,Thanks for your advice. Wish I had found this forum before doing the prep work.I'll let you know what happens. I am an old Virginia boy myself.I was raised in Richmond.Thanks for your time. James

 

[Rob Z]

James,

which brand of SLC did your contractor use?

PS Whereabouts in Richmond? We lived there from '67 to '72.

 

[bootsmckiber]

When you come to setting your trav definatly use white thinset,you'd be surprised at how much moisture natural stone can absorb,this is the guy who used regular thinset under travertine :mad2: He's been there for ten years,can't quite forgive himself,good luck,wear a mask.
Mike

 

[inspiredandy]

Good luck with it James, keep us posted on the progress