Gap between cinder block wall and basement floor

I'm fixing up my workshop in the basement. The floor is a concrete slab, and I plan to cover it with vinyl/ rubber tiles. Moisture is not a problem.
There is a gap between the slab and the cinder block walls. This gap is only about 1/8" wide at two of the walls, but along the long wall the gap widens in a few places to about 1". Along the edge of the slab there is insulation, some kind of Styrofoam. The top of this insulation has deteriorated somewhat over the years (the house is 20+ years old), but looks reasonable. In most spots, the gap is only about 1/4" deep (some loose insulation chips, small "rubble" is visible), but for about 3-4 feet the gap is much deeper, about 1 - 1 1/2". Again, there is some "rubble" visible in the gap. Using a flashlight, I can see a space between the insulation and the foundation wall, but I can't see how far down this space goes, for obvious reasons.
I was thinking of sealing the gap (the top section that is) before laying the tiles (now or never...). Cement is the obvious choice, but I've heard of this thing called "temperature" and "expansion". That's what I get for watching all those DIY shows. Ignorance is bliss......
So, I thought about cutting a strip of thin board (1/8"), place this in the gap against the wall, and then fill the gap with cement, effectively using the board as a form. That should leave enough room for expansion. What material would work best? Vinyl concrete patcher? Some sort of epoxy? Ordinary cement?
Thanks.
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Perhaps you should leave the gap as it is and just place baseboard along the walls. That way if the slab needs to move it can.
--
Roger Shoaf
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People will probably scream but I have seen tile layers fill this kind of gap with thinset mortar more than once. No it's not really intended for that but I have torn up installations where it had been done years before and still looked fine. You might want to just partially fill the wide areas and leave whatever can be easily covered with quarter round or baseboard for expansion as somebody else suggested.
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This stuff is made specifically to address your problem .. .. ..
http://www.latexite.com/pr-crkstix.html

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My basement is above ground on the back and side walls and is half finished (a third side). Has unused French drain. I framed and insulated the exposed sides and covered with painted peg board making it great for hanging tools and things. Floor painted but if tiled would not show gap. I think you should leave yours alone and not fill it.
Also there is no such thing as a dry basement. I've had 2 minor water excursion incidents in the 30+ years I've lived here, both due to not maintaining draining from downspouts. Simple extensions solved problems but any time rain water hits side of house, there is potential for water in basement.
Frank
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I agree with Frank. I have a similar set up....finished basement with cinder wall and concrete slab floor with a small gap. I also had some minor water issues and was GLAD the seepage went down the gap and not puddle on the concrete floor.
If you really want to seal the gap, why not use the "foam in a can"? It comes in a "gap filler" formula for larger spaces. From experience, don't try to wipe away any excess when wet. Just let it harden up, then trim with a razor knife.
--Jeff
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