Former real estate appraiser here, albeit commercial, not residential.
Renovations that will increase value generally consist of increasing the size or quality of the home, or decreasing the effective age. Correcting an issue like a single bathroom in a 3-4 bedroom house, or reconfiguring the house to match what buyers want (i.e. open floor plan or walk-in closets) can return more than the cost of the renovation. Homes consist of short-lived components (flooring, water heaters, mechanical systems, etc.) and long-lived components (electrical wiring, frame, foundation). New flooring, new kitchen or bathroom fixtures, etc. are visible signs of better quality or newer components. Fixing issues with the foundation, plumbing, electrical, etc. are usually deferred maintenance and will rarely return dollar for dollar what you spent.
Buyers expect the roof to not leak, the foundation to be in good condition, etc. Having a new roof might add a bit of value, but most buyers won't distinguish between a 3-year old roof and a 13-year old roof as long as they both look to be in good condition with no leaks.
What you're describing sounds like it will not result in much of an increase in value. However, if this is deferred maintenance it might significantly reduce your buyer pool. Most people looking in that price range do not want to worry about a $20,000 repair. Either they'll want a deduction in the price for the estimated cost of that deferred maintenance, or they'll just skip over your property and look for something without any obvious problems. This could be something that wouldn't be revealed until a home inspection but that that point you've now invested time, and probably money, into the process.