How to read a siding estimate
A siding estimate is usually one page of shorthand written for other tradespeople. Once you know what each line refers to, the gaps become obvious — and the gaps are where change orders come from.
The measurement line
Siding is priced by the square (100 square feet). A bid that gives a lump sum without a square count cannot be compared to another bid. Ask for the square count and whether openings were deducted — different estimators handle windows and doors differently, and that alone can move a bid by thousands.
Overlay vs. tear-off
An overlay installs new siding over the existing wall covering. It is cheaper and faster, but it hides rot, prevents inspection of the sheathing, and can complicate flashing at windows. A tear-off exposes the sheathing so damage is found before it is buried. Your estimate must say which one you are buying, in those words.
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Line items that should appear
- Water-resistive barrier (house wrap) by product name, with taped seams
- Flashing at windows, doors, decks, and roof-to-wall intersections
- Trim, corners, and J-channel — material and color
- Fasteners appropriate to the siding type
- Per-sheet or per-square-foot price for sheathing and rot repair
- Caulking and paint or factory finish, and who touches up
- Disposal, dumpster, and final site cleanup
- Labor warranty length, separate from the material warranty
Shorthand you may see
| Term | What it means for you |
|---|---|
| T1-11 overlay | New siding installed over existing T1-11 plywood panels — no sheathing inspection |
| SQ | One square = 100 square feet of wall area |
| WRB | Water-resistive barrier — the wrap behind the siding |
| J-channel | Trim channel that receives siding ends around windows and doors |
| Blind nailing | Fasteners hidden under the course above; correct for most lap siding |
| Rainscreen | A drainage gap behind the siding; adds cost, adds drying capacity |
What to ask before you sign
Send this: 'Is this an overlay or a full tear-off? What is the square count, is house wrap included by name with taped seams, and what is your per-sheet price if you find rot?' The answers turn a one-page bid into a comparable scope.
Frequently asked
- Why do two siding bids differ by so much?
- Usually because one is an overlay and the other is a tear-off, or because one includes wrap, flashing, and trim replacement while the other reuses existing trim. Match the scope before you compare the price.
- Should rot repair be in the bid?
- It cannot be priced in full before the wall is opened, but a per-sheet or hourly rate should be written down in advance so the repair is not an open-ended charge.