Some of it, yes — and we would rather tell you which parts than pretend everything needs a contractor.
Worth Doing Yourself
Downspout extensions. The single highest-return job on this list. Getting roof water four to six feet away from the foundation costs very little and solves a meaningful share of crawl space water problems outright. If you do nothing else, do this.
Regrading close to the house. Building the soil up so it falls away from the walls, a few inches over the first six feet. Some soil and an afternoon.
Clearing debris. Old insulation, cardboard, construction offcuts. Wear a respirator and coveralls, and do not do it if there is visible heavy mold growth.
Buying a humidity sensor. Twenty or thirty dollars, sits in the crawl space, reports to your phone. It turns an invisible space into a measurable one and it will tell you whether you have a problem at all.
Worth Paying For
Anything structural. Jacking a floor is not lifting a heavy object — it is redistributing load through a building, and doing it too fast cracks everything upstairs. Footings need sizing for the soil.
Drainage design. Deciding between exterior correction, interior perimeter drainage and a sump requires diagnosing where water comes from, and getting that wrong means doing the expensive version of the wrong job.
Full encapsulation. The materials are not the hard part. Sealing seams properly, terminating at the walls, wrapping piers and sizing a dehumidifier are, and a liner that is nearly right performs like one that is not there.
Mold remediation at any scale. Respiratory risk, and disturbing growth without containment spreads it into the house above.
Where DIY Attempts Usually Go Wrong
Using six mil plastic because it is what the hardware store sells. Overlapping seams without taping. Sealing the vents without lining the ground or adding a dehumidifier, which traps the moisture in. Putting a domestic dehumidifier in a crawl space, where it runs continuously, ices up and fails within a season.
The Honest Framing
Do the outside work yourself. Measure the humidity yourself. Then get an assessment and decide with a number in front of you.
If it turns out downspouts and a liner would do it, we will tell you that, and it will be a small job.