YouTube makes everything look like a Saturday project. Some of it genuinely is. The rest costs more to fix than it would have cost to hire right — and a few categories can injure you or void your insurance. Here is the framework.
1) What is failure worth? A crooked shelf costs nothing; a failed shower pan costs $8,000 in subfloor rot. 2) Is it reversible? Paint is; gas fitting is not. 3) What is your real hourly rate? If a pro does it in 4 hours for $400 and it takes you two weekends plus $150 in tools, DIY "savings" may be negative.
Interior painting, hardware and fixture swaps (with the breaker off), caulking, small drywall patches, landscaping and planting, flat-pack assembly, smart-home devices, appliance installs that plug in, laminate flooring in simple rooms. Failure cost is low, materials are cheap, and mistakes are visible before they compound.
Anything structural, roofing (falls are the #1 DIY injury), electrical beyond fixture swaps (fire risk hides in junction boxes for years), gas lines, shower waterproofing, foundation and drainage work, tree removal near structures, and garage door torsion springs. These share a pattern: invisible failure modes with catastrophic costs.
Unpermitted DIY electrical or plumbing can void insurance claims — adjusters look for permits after fires and floods. At resale, inspectors flag amateur work instantly, and buyers discount aggressively. When a job legally needs a permit, that is the universe telling you which column it belongs in. Post it on ConstructHelp, compare a few real bids, and decide with actual numbers.
Post your project once — verified, insured local pros send you free competing quotes, and escrow protects every payment.
Get 3 Free QuotesRoofing, structural changes, gas work, main-panel electrical, shower waterproofing, and garage door springs — the failure modes are injury, fire, or five-figure hidden damage.