I have a 125 year old townhouse with a large (700 sq ft) basement. We had waterproofing done (vapor barrier, perimeter drains, sump pumps) last year that dried everything out and made the space usable. We would like to finish the basement by adding walls and a floor. The problem is the relatively thin concrete slab that has a few spots where it swelled up, and other spots that go down, mostly in the range of 1-2 inches. I was able to knock down the highest spots with a sledge hammer, and can patch those as necessary. But I’d like to put down a vinyl plank floor and don’t know what the best way is to level everything. Self leveling concrete seems like it would work, but it would be expensive. A full subfloor with shims is an option, but that seems excessive too. I don't really care about it being actually level - I just need it flat enough for a vapor barrier of some sort, thin underlayment and vinyl plank. What’s the best option for topping old concrete in as needed between 1/2 to 2 inches? The floor right now seems stable - most of the issues were moisture related.
Leveling compound really is the way to go with this job, are there any tricks to save money on doing it - I am sure there might be. But it is always cheaper to do it right the first time than to do it right the second time.
This is the area where most people make the mistakes : COSTS. To do something right costs this much and they don't want to spend the money, so they do it wrong, later they have issues and wish they had done it right - some then ask a pro to come in and do it right (More money) others tear up what they have and do it right the second time (More money). Then you have the others who simply sell the house to an unsuspecting soul and go their way, possibly to make the same mistake in their new home and never learning this simple rule..
Cheaper to do it right the first time than to do it right the second time.
I know it will cost you up front, but in the long run it will be cheaper both in terms of laying your flooring and having it right. You could even put heating elements under the plank if you were so inclined.
Throw some shingles to build it up. When starting out I thought this was a lazy way to do it but then found out some old timers told me it's the way to go! They don't go bad regardless of the situation. Last basement I I put my leveling compound on top of the shingles which saved quite a bit of money!