In an act of spontaneous stupidity, I decided to rip up the flooring in our finished basement to put tile down. My work schedule is insane, my wife's pregnant, I have no spare time... so deciding to do this now made no sense; yet here we are.

I had assumed the concrete would be semi-level, and I could make up the difference with mortar when I put the tile down, no. It appears someone, at some point had dug up the center of the room (I assume to take out an oil tank or something, and instead of repouring the entire floor to make it level, they just filled the hole. From random parts of the center of the room with the new concrete to the wall there's anywhere from a 1" to almost 2" gap.

A contractor friend that owns a huge kitchen and bath company walked me through what I need to do, I spent WAY more on materials than I had planned, and can't figure out how to execute. He wanted me to put furring strips around the perimeter and level them, pour a 50/50 mixture of shower liner mud and thinset with a latex additive, and a coating of "red coat". That's all fine and good, but the furring strips aren't level, if I make them level I'll end up taking the floor up like 3" overall which I'm not doing.

At I missing something?

The lighter area in the middle seems to have the highest point, but also dips in the middle



And a few with a 7' level from the center to the walls, using 10mm thick tile spacers to measure.



Nothing is level anywhere, and I'm completely lost



And the front porch, and main bathroom... the wife isn't happy






I'd love some insight from the knowledge base. I'm sure we have a concrete basement leveling expert here haha

The firing strips don't need to be level. Just high enough that the mix doesn't flow over them. The mix, if done correctly will self-level itself. The mix should be really soupy so you can pour it onto the concrete. With will flow to the low spots.

Can you just fill the low points and assume there will be a little slope?

In a perfect world it would be flat and level. In reality you can have it either or none. If there's a floor drain you should have a slope towards it. If not having it flat will look just fine and unless someone puts a level or rolls a marble on it you likely won't know unless it's really out of level.

Oil tank?

Dead body?

There are not oil tanks dead center in ground in basement.

Any missing persons associated with this house's history?

I'm an an avid DIYer and former remodeling contractor; but sometimes it really is worth it to call in professional specialists.

The floor need not be level just smooth. For tile super smooth. If this was my project I would fill the low spots then install one of the floating floors.

I'd use regular concrete for the super low areas and then go back with self leveling.

If I were you I’d throw some astroturf over that and move all the crap downstairs out of the main bath and off the porch before my pregnant bride beat my brains out with an iron skillet while I was asleep.

quote:

Originally posted by arfmel:
If I were you I’d throw some astroturf over that and move all the crap downstairs out of the main bath and off the porch before my pregnant bride beat my brains out with an iron skillet while I was asleep.

Spoken like a wise man!

Self leveler is expensive. Firring strips are time consuming and you can build in an error.

Step one:

Clean the floor thoroughly, no dirt dust or oil.

Step two:

Apply a concrete bonding adhesive

Step three:

Use a tile base like this product. You mix it with just enough water to wet it, so it can be skreed with a level, packed, and walked on while you work. I'd recommend actually mixing it on the dry side, leveling, and then adding water to the near finished subfloor.

This is the best mix of cost/time/result that I've found.

You could also use this product on the deepest areas, then apply a self leveler on top, out to a feather edge if called for.

With any product, I would still apply a concrete bonding or vinyl tile adhesive to the original floor.

Grinding that area with a varied 1-2" thickness would be very, very dusty, and at 2", you're close to the typical thickness of a basement floor, if it is only a "rat slab" and not pretensioned or otherwise structural.

Grinding is for small areas of imperfection, and should only be considered if controlling dust is practical. Grinding large areas or large thicknesses, is generally to be avoided.

I agree that trying to make it all level isn't realistic. Just fill in the low spots as best possible so your finished floor doesn't sag in places.

As an aside, when someone is asking for help like this, if you feel compelled to write "I'm not a professional but.." or have no direct experience of your own, please just stay out of the thread.

Advice given without direct knowledge or experience, is more folly than assistance.

Wanting to help, isn't the only criteria for actually helping.

As a "Professional Contractor" I have to agree with Arc for the most part.
Given the size of the project I would first consider using a tile mason to get the project done..
If that was not an option I would use a bonding agent like Arc said but would instead use a self leveling mix like this:

https://www.lowes.com/pd/High-...s59fI6kaAg0vEALw_wcB

But pay attention to the amount of water used.
I agree with the other comments that you should not try and get it perfectly level but close enough...

Depending on the size of the tile you plan on using (smaller tile is much easier to work with on an uneven surface) some sort of self leveling compound can be used to fill in the low spots and the rest can be be compensated for with extra thinset, just make sure you start your tile at the highest point The Red Guard is an elastomeric membrane for waterproofing and crack prevention and probably isn't needed unless the concrete already has some cracking. Too bad your not closer, because if you did need it Ive got about 25 gallons of it in my garage.

And yes Arc, I am a supervisor for company that does commercial and residential flooring and counter tops.

Thanks guys, I will admit I'm in over my head, however I am pretty good with tile work, and generally pretty handy. I got an 8' level and a laser level to find the ridiculously high sport..then beat them with a hammer. I agree I'll be happy with flat vs level.. unfortunately in bought 12x24 tiles to make the job easier. So far I've broken up the really high areas and need to concrete them in. I think the job is overwhelming because of the size.. bathrooms I had no problem ripping up, backerboarding, leveling, tiling grouting etc. I'm thinking I'll break this down into bite size pieces and frame the floor in three sections. Get one poured and set then level the next off that. I'd love to use a self leveler, it's just too big a Gap to make up with it

My only experience, which is somewhat limited, is that the fast setting self leveling stuff needs a LOT more water than the instructions say.... fast set needs to be like thin soup or it will set up in a matter of a few minutes. And by a few I mean like 3 or 4!

quote:

Originally posted by arcwelder76:
Grinding that area with a varied 1-2" thickness would be very, very dusty, and at 2", you're close to the typical thickness of a basement floor, if it is only a "rat slab" and not pretensioned or otherwise structural.

Grinding is for small areas of imperfection, and should only be considered if controlling dust is practical. Grinding large areas or large thicknesses, is generally to be avoided.

Dust. Lots of it. The one time I rented a concrete grinder, I taped the entire room off with plastic except for the door wall. I opened those and had a big orange fan blowing the dust out to my lani. Fifteen minutes after I started, a firefighter walked emerged from the dust and scared the bejeezus out of me. Apparently, my neighbors thought my house was on fire.