Hello all and thank you in advance for your help! I always get straight answers here.

I have turned my attention to finishing my basement. The first order of business is to finish my gun vault. I have a 1/2" thick steel in-swing vault door that leads to approximately 175 sq ft of finished space that is located underneath my front porch. The walls are all 10" steel reinforced concrete. I have framed it out, wired it, drywalled it, painted it and am starting to do the finishing touches. I am at the point where I am ready to tile the floor. I bought some white ceramic tile to go down and started to lay the grid down so I know where to start to make the spacing and reveal as perfect as possible.

I finished last night... Beat after installing white oak wainscoting and black tactical slatwall. I happened across one of those Holmes on Homes shows. He just happened to be reviewing someone's basement and was noticing stress cracks in the concrete floor. Just about every basement floor I have ever seen shows some sort of stress cracks but this guys were a little too much I suppose. The guy started tapping the floor with a hammer... Listening to the difference in sound. A void under the concrete surely makes a different sound! I have two stress cracks in my vault and others in my basement where I eventually want to finish as a game room. I thought I would do the same thing.

I was surprised to hear the distinct difference of sound letting me know there was a void below the cracks. Not large areas but now it concerns me. The guy on TV said this sometimes happens normally but is usually where the excavator took out too much ground and then replaced it to level it all out. You can never compact it like it was... So it recedes, leaving a void.

Their fix was to have a company come in, drill a bunch of holes in the floor and pump in a slurry of high density expanding foam of some sort. Seemed logical enough to me. Then they seal the holes with hydraulic cement.

My question is... Should I have this done? The house is coming up on 5 years old and was a custom build. Generally I haven't had any issues with anything and have had all the builder's work inspected over the years with no glaring faults found.

I'd appreciate the pros input here. Do I call someone out? Or is this just a normal thing with all houses? Am I worried about nothing? Should I just go ahead and tile? I imagine I have another 5-10 years here and I'd like to make sure I won't end up with cracked tiles now or later, even after I am gone. I'd like to do this right!

Thoughts?

 

If you tile directly to the floor, and if you get cracks, the tile will crack also!

I like his shows but some times I questions the extreme solutions he does, I guess if the budget is unlimited why not.

What you could have done is install a crack isolation membrane on the floor which will isolated the tile and prevent cracks!

 

Yeah... I know he goes to extremes at times but I also see some of the crap people do that he uncovers! The Schluter membrane is a great idea... I'm delaying tiling to put it down! Thank you!

I am still curious about filling the voids however...

 

That is a new one for me!

 

I think I found the answer after a little research on the web. Might not be a good idea... But I'd still like to hear from an expert. I found this online...

"While your idea of adding fill to the void under your basement floor slab may seem like the correct action, it is not. The void under the slab has developed because of the yearly cycles of swelling and shrinking of the clay soil underneath. While this may become less severe with age, it won't completely disappear in the future. By filling this area and patching the crack, you will only be accelerating further damage to the floor slab when the soil expands, again."