How to compare siding bids line by line

You compare siding bids line by line by normalizing them onto one scope sheet — every required line item down the side, each contractor across the top — and filling in each bid’s number or “not included” for every line. This converts three documents that look nothing alike into one apples-to-apples grid that instantly shows what a low bid left out, turning “cheapest” into “cheapest for the same complete project.” Without normalization, you’re comparing prices for different work, which is how boards approve a number that balloons.

This page gives boards and managers the exact method, with a worked example.

Why can’t you just compare the bottom lines?

You can’t compare bottom lines because three contractors rarely bid the same project — one includes tear-off and a rot allowance, another excludes both, a third bundles trim while a fourth leaves it out. The bottom-line totals describe different scopes, so “cheapest” is meaningless until you’ve made the scopes identical. A $40,000 spread between bids almost always reflects different included work, not a better deal.

This is the core risk of multifamily siding procurement: the cheapest bottom line is frequently the most incomplete bid, and its omissions return as change orders mid-project. The fix is to stop comparing totals and start comparing line items — which requires you to have first defined the line items in the RFP and bid format. See what a real siding bid must include.

How do you normalize the bids?

You normalize bids by building one scope sheet: list every required line item in the left column, put each contractor in a column across the top, and fill in their price for each line — writing “not included” wherever a bid omits one. The moment a cell reads “not included,” you’ve found a difference that would otherwise hide in the total. Then add each column to a normalized total for the same complete scope, adding back reasonable estimates for any omitted items so all bids cover identical work.

Steps to normalize:

1. List every required line item (material, tear-off, rot allowance, WRB, flashing, kick-out, trim, disposal, access, resident plan, permit, warranty, alternates).
2. Enter each contractor’s number per line; mark omissions “not included.”
3. For any “not included” item, add a reasonable estimate so every bid covers the same scope.
4. Re-total each column — this is the true apples-to-apples comparison.
5. Note non-price differences (warranty length, schedule, references) alongside the totals.

What does a normalized comparison look like?

A normalized comparison looks like a grid where omissions and warranty differences jump out, often reordering which bid is actually cheapest. The grid below is an illustrative model, not an actual project — the numbers are placeholders to show the structure, and you’d fill in your own bids’ figures:

The lesson the grid teaches a board: Contractor A’s “lowest” total was lowest because it excluded tear-off, the rot allowance, and trim — once those are added back, A is often the most expensive and carries the weakest warranty.

How do you weigh price against everything else?

You weigh price against everything else by scoring bids on the criteria you set in the RFP — scope completeness, normalized price, warranty, schedule, and references — rather than price alone. Once bids are normalized to the same scope, price differences shrink and the non-price factors (a contractor’s occupied-building experience, warranty length, and resident-communication plan) often become the deciding factors. A modestly higher bid from a proven multifamily crew with a 50-year material warranty can be the better fiduciary choice.

A simple weighted approach the board can document:

• Scope completeness — does the normalized bid actually cover everything? (gate: incomplete bids drop out)
• Normalized price — total for identical work
• Warranty — material and labor terms
• Experience & references — occupied multifamily track record (questions to ask)
• Schedule fit — within your construction window

Document the scoring in the minutes so the award is defensible at the annual meeting.

When should you have a professional review the bids?

Have a professional review the bids when the stakes, the spread, or the omissions are too large to judge in-house — which is common on six-figure occupied-building projects. A bid-scope review checks each proposal against the complete Replacement Scope Map, flags missing or underpriced line items, and normalizes the comparison so the board sees the true picture before a vote. It’s cheap insurance against approving a low bid that becomes a budget overrun.

That is what a siding bid scope review does — it runs the bids you’ve actually received against the complete checklist and hands the board a normalized comparison. Whether you do it in-house or get help, the rule holds: don’t let a board approve a number until every bid has been normalized to identical scope. Pair this with a clean RFP up front and the comparison step becomes straightforward.

Reviewed against public source material from Ben Juncker and Craftsmans Choice, without presenting their contractor credentials as this sites own.

Frequently asked questions

Q: Why is the lowest siding bid usually the most expensive in the end? Because it’s frequently lowest by omitting tear-off, the rot allowance, the WRB, flashing, or trim — work that returns as change orders mid-project. Once you normalize all bids to the same complete scope, the “cheapest” bid often becomes the most expensive.

Q: How do I compare bids that use different materials? First decide whether material is fixed; if so, any bid with the wrong material is non-conforming. If you’re comparing materials intentionally, normalize each bid to the same scope per material and compare within each material, factoring lifespan and warranty differences (e.g., LP 50-yr vs Hardie 30-yr).

Q: What if a contractor refuses to itemize? Treat it as a red flag. A contractor who won’t break out tear-off, the rot allowance, flashing, and trim is either unable or unwilling to be compared — both are reasons to be cautious. Your RFP should require itemization so this surfaces before the award.

Q: Should I always pick the lowest normalized bid? Not automatically. Once scopes are identical, weigh warranty, occupied-multifamily experience, references, and schedule. A modestly higher bid from a proven crew with a stronger warranty is often the better fiduciary choice. Document the scoring for the board.

If the spread between your bids is large or the omissions are hard to price, a siding bid scope review normalizes them for you before the board votes.

Last updated: 2026-06-27. Part of hiring and bidding.