Siding quotes on one house commonly spread widely, and the spread is usually real work rather than margin.
1. Tear-off, or over the top
The single largest scope difference. A quote that includes removing the existing siding and disposing of it is a different job from one that goes over it.
Both are legitimate. They are not comparable, and a quote should say which it is.
2. The weather barrier and flashing, specified
What WRB, and whether the openings will be flashed. On a tear-off this is the item that decides whether the wall stays sound.
"Housewrap included" is a start. Naming the product and stating that windows will be pan-flashed and head-flashed is better.
A quote silent on flashing is quoting siding rather than a wall.
3. Sheathing repair, with a unit price
Nobody knows how much rot there is until the old siding is off. What can be agreed beforehand is the rate — per sheet or per square foot.
A quote with no provision at all will produce a conversation about money at the worst possible moment, with an open wall.
4. Material and trim, by name
Manufacturer, product line, profile, exposure and colour for the field. And the trim: corner posts, J-channel, starter, utility trim, soffit and fascia if included.
Two quotes naming different product tiers are not comparable, and the tier is where a cheap quote often finds its saving.
5. What else is included
Soffit and fascia. Gutters removed and refitted, or replaced. Shutters, vents and light blocks. Removing and refitting the deck rail or the awning.
Each is an item that either appears on the invoice later or does not get done.
6. Disposal, permits and restoration
Skip hire and disposal. Permit, where required. Landscaping and paving protection, and what happens to the plants under the walls.
The two questions that reveal the most
"What do you expect to find behind the siding?" On any house older than about thirty years, the honest answer names possibilities — rot below windows, missing flashing, a second layer. A contractor who expects nothing has not looked.
"How do you handle expansion on vinyl?" or, for fiber cement, "How do you treat butt joints?" Both have specific correct answers, and someone who gives them has installed the material properly before.
What to verify independently
Licence and insurance, from the issuing body. References from jobs several years old rather than last month — siding problems appear with time. Photographs of a wall they have wrapped and flashed, mid-job.
That last one is the most revealing request you can make, and a good contractor will have them.
The payment structure
A deposit, progress payments tied to milestones, and a meaningful holdback until completion.
The final details on a siding job — trim, corners, clean-up, the small returns nobody can reach — are what it is judged on from the street, and a fully-paid job rarely gets them finished with the same attention.
Where a very low quote is coming from
A quote materially below the others is usually explained by one of four things: no tear-off, a lower material tier, no flashing work, or no allowance for sheathing repair.
None of those makes the contractor dishonest. All of them make the number incomparable, and asking which it is turns a suspiciously cheap quote into a different scope you can decide about.
Occasionally the low quote is simply a crew with lower overheads doing the same work, and the six items above are how you tell.
Timing the decision
Siding contractors are busiest in the warm months and quote accordingly. A job booked in autumn for the following spring frequently gets a better price and a better crew than one booked in June for July.
That is worth knowing when a quote comes with an expiry date attached.