Tiling a concrete floor after carpet removed

[doctordun]

Hello,

I just joined this forum and have enjoyed reading a lot of informative posts. I can't find one the matches my specifice question.
We had water damage and had to remove all our carpeting. Taking this opportunity, we decided to replace our flooring with ceramic tile.
We have two issues:

On part of the concrete floor, the builder used it as a place to paint the trim molding. There are wonderful painted stipes on about 15% of the floor.

In our living room and dining room, there is one each, a long hairline crack.

From what I read, I need to sand off the paint. Correct?

I also read that I need some sort of underlayment for crack isolation. Is that also true?

If I need the crack isolation, what is the least expensive method. In today's economy and a fixed income(I'm retired), I need all the help I can get.

Thank you for any and all advice.

Doc

[doug boardley]

Hi Doc, yes ideally you want to remove the paint, you could maybe try one of these from tradetiler

as for crack isolation, are these new cracks that have appeared recently?

[Dave]

Hi Doc and firstly welcome..

If the paint is just thin lines along the floor then it will be fine for those parts to stay.. they are not going to hinder the adhesive.

Now to these cracks.. do they run in straight lines.. were they there before you laid the carpet.. they could just be cracks from when the floor was first laid and as it dried out and shrank etc.

[doctordun]

The paint is several 4 inch wide or so lines.

The home is 10 years old and this is the first time I've actually seen the concrete, so I don't know how long they have been there.
The cracks are not straight line. One appears to be edge to edge and the other is near the middle of the room.

[Dave]

OK.. then as above and remove the paint..

Personally i think if the cracks are just hairline then they will be ok... but an anti crack membrane will make sure if you are worried about th em..

Some pics would help us decide if they are bad enough to warrant one.

[doctordun]

Here are a couple pictures of what I am dealing with:

By doctordun at 2010-08-31


By doctordun at 2010-08-31

[hillhead]

The cracks don't look too bad at all,a good flexi adhesive or even better an S2 grade should work ok.

[Ajax123]

Those cracks are classic plastic shrinkage cracks and are most likely to have been there since the concrete was first laid. If there is no heating then there is really very little to worry about in respect of movement etc. I assume this is not a brand new house so that any realistic expectation of long term shrinkage is long passed. There are a few ways you could deal with them if you really want to.

1. Surface dress them by sprinkling waterr onto the concrete and leaving it for a few hours (till it looks dry again) then brush into them neat portland cement. This is a classic repair method for these types of cracks although they would nortmally be done when the conrete is still relatively fresh. The method more hides than repairs and in this instance is probably not worth the effort.

2. If you are really worried about them then you could epoxy resin fill them. This would be appropriate if there were underfloor heating as expansion and contracton would need to be considered

3. Use an uncoupling mat

However in all honesty I would not bother repairing them as they are unlikely to move and as such will not cause a problem witht he tile face.

[Dave]

I agree with Alan.. those are fine IMO.. just cracks from the screed installation when first laid..

[doctordun]

The cracks don't look too bad at all,a good flexi adhesive or even better an S2 grade should work ok.

New terms to me.
Thinset is all that's been recommended.
What is S2 Grade?
What flexi adhesive should I look for? My limited searching has found only a thinset that is basically a form of concrete.

Thanks again for all the replies.

[Ajax123]

question from me - if the concrete is old and unheated and has pretty much done all the moving it is going to do why would a flexible addy be required?

[whitebeam]

Flexis tend to be the standard nowadays

[peckers]

In this situation a flexible adhesive wouldnt have to be used as long as it is a ceramic tile being used, and not a porcelain, but as whitebeam has said a single part flexible adhesive is mainly the norm now a days, and the way i tend to look at it for only a little more per bag it is worth having for piece of mind. Its a bit like when buying a car pay a bit extra for an extended warranty or so to speak

[doug boardley]

New terms to me.
Thinset is all that's been recommended.
What is S2 Grade?
What flexi adhesive should I look for? My limited searching has found only a thinset that is basically a form of concrete.

Thanks again for all the replies.

an american term for cement based tile adhesive
S2 grade is a highly modified adhesive for areas where there is likely to be movement
depends on what is available locally to you

[vistatiling]

Search online for Ultra ProFlex SP+ES it is a standard drying flexible adhesive with Lifetime Product Guarantee & you will get it at the decent price