Estimating home work is harder than it looks. The gap between a profitable bid and a money-losing one often comes down to small oversights that compound. These are the five mistakes we see contractors make most — and how to fix them before they eat into your margin.
1. Underestimating demo and disposal
Most contractors bid the “install” work but leave demo as a line-item afterthought. In Florida, a bathroom demo can easily run 15-20 labor hours once you factor in asbestos surveys (required in pre-1980s homes), tile removal, and proper dumpster staging. Budget 2-3 hours minimum per bathroom, plus $400-$600 for disposal. It's often the single most under-bid category.
2. Forgetting contingency labor
Old homes hide: galvanized pipes, ungrounded circuits, structural rot, and worse. When you discover framing that needs replacement or electrical that needs rework, the difference between a 4-day job and a 6-day job is pure margin loss. Build a 10-15% contingency into every estimate for surprises. When there are none, you're ahead. When there are, you break even instead of losing money.
3. Bundling permit and inspection costs
Permits are direct costs — pass them through to the client as a separate line at county price, no markup. But inspections often require a revisit ($80-$150 for travel + time), and failed inspections mean another trip. List the permit separately and budget 1-2 inspection revisit hours as contingency. It clarifies the quote and protects your margin when things don't pass first try.
4. Guessing material availability
Tile, fixtures, and lumber have lead times. If your estimate includes a 2-week fixture lead time but the client finds the fixture is on a 6-week backorder, the job starts late and your crew is unpaid waiting. Always confirm availability before quoting, and tell the client the lead time explicitly. If they want something faster, they pay for expedited shipping or accept a different product.
5. Not charging for change orders upfront
The quickest way to kill margin is doing change work at your standard rate without a written amendment. If the client says “can you just move the outlet?” and it takes an hour to reroute, you need a 10-minute conversation and a written change order, not a handshake agreement. Spell out markup clearly in your original contract — most pros do 15-20% for mid-job changes. Document it and you stop giving away profit.
How to estimate better
- →Photo documentation: Take photos of the existing work, finishes, and condition before quoting. They catch details you might miss and prove scope later.
- →Separate labor and materials: Always quote materials at cost (or cost + 10-15%) and labor at your hourly rate. It makes scope changes calculable mid-project.
- →List contingency explicitly: Tell clients “I've budgeted 2 discovery hours. If we find something that requires additional work, I'll get your approval in writing before I proceed.” Transparency prevents disputes.
- →Use a change order template: Every time a client requests out-of-scope work, issue a written amendment with the new cost and timeline. It takes 5 minutes and saves thousands in disputes.
The best estimates aren't the lowest — they're the ones that account for reality. Build margin into every line, and you'll close more jobs profitably.