Flooring Tile - Tiling a concrete slab in unheated space

I have a covered and enclosed porch (screens in summer; windows in winter- location eastern PA). I am planning to tile with porcelain using modified thinset on a 4" concrete slab. The floor was originally covered with in/out carpet. Do I have to TOTALLY remove the old rug adhesive, or is scraping it down best as possible acceptable? Or am I looking at have to apply an adhesive solvent?:confused:

It would be difficult to remove all the adhesive without renting a concrete sacrifier or grinder. Have you tried using a floor scraper? I would not recommend any solvent based removers because they usually have a very powerful off gassing.

Oh yeah. Tried ammonia, TSP, Soilax; turpentine; laundry detergent; dish washer detergent with scrapers, scrubbers and flat nosed shovels. I'm not 100% down to the concrete but can see spots where it is. So is close enough good enough???
:wall:

I would say you are fine. As long as you don't have high spots.

Use a good modified thinset like Flexbond or Versabond.

Great! No high spots. planning on using Versabond. I'll let you know how I make out. Many thanks, JoeP :)

Joe

Solvents shouldnt be used on a concrete slab that you intend to tile. The solvents and the adhesive you are trying to remove can seep into the slab clogging the pores of the cement and preventing a good bond with the thinset. Always mechanically remove any adhesives from a slab, never use solvents. You can test the slab by pouring some water on it. If the slab absorbs water its ok.:)

You dont say if this is heated space (or did I miss that).

Porch slabs can be subject to great fluctuations in temperature in the different seasons and with direct sunlight and those temparature fluctuations cause expansion/contraction and different materials do that at different rates. An isolation membrane in a porch like yours is often good insurance as it will help manage that movement. I know it adds a lot to the cost of the job.:)

If you have any cracks in the slab, you'll need to evaluate them.

How big is the floor? You may need to incorporate some movement joints, specially if the room gets a lot of sun.

The porch (unconditioned) measures 11'x19'. No cracks in the slab. Slab was poured 40years ago, so I think it's pretty stable at this point. Hadn't thought about an isolation membrane. Really feel it is necessary???

Hadn't thought about an isolation membrane. Really feel it is necessary???

I dont think its absolutely necessary. As I said its just added insurance. Your call.

The porch (unconditioned) measures 11'x19'.

Its sometimes difficult to access whether you need movement joints or not. TCNA recommendation for indoors is 20' to 25' and outdoors is 8' to 12' in each direction. For indoors with exposure to direct sunlight its 8' to 12'. Your space is not heated. You may want to consider a movement joint along the 19' length if you have direct sunlight in the porch. Its close and your call.

HeresJohnny, What would you recommend for an isolation membrane and a movement joint?

Joe

Schluter ditra and Noble CIS are 2 good membranes.

As for a movement joint, if you need any at all, it would be one along the 19' length. Do you get alot of direct sunlight in the room?

HeresJohnny: I would say for the most part no direct sunlight. What's your opinion on RedGuard as an isolation membrane?

I would say for the most part no direct sunlight.

You can probably get away with no movement joint, maybe. If you decide to add a movement joint, it can be something as simple as a caulk joint (color matched caulk instead of grout) about 12' or so into the layout. You could try to put it into the least conspicous place as it will be slightly noticeable.

What's your opinion on RedGuard as an isolation membrane?

Ive more used redgard as a waterproofing on walls than isolation membrane on floors, although it can be used as such. I think the sheet membranes are better protection against crack isolation.

Thanks for all the suggestions and help. I'll let you know how I make out. I plan to order caulk to match the grout as I want to caulk between the tile and a finished stucco wall.
Again, thanks, Joe