How to Compare Waterproofing Quotes
Comparing waterproofing quotes on the total alone tells you almost nothing. Two numbers for the same roof usually describe two different jobs. This is what to look at instead.
Why the totals are rarely comparable
Waterproofing has no fixed rate per square metre, and any figure quoted before someone has seen the building is a guess. Material is a small share of the cost on most residential jobs. The rest is preparation, access, detailing and what the substrate turns out to be doing underneath, and none of that scales evenly with area.
That is why a per-metre rate from one job tells you nothing useful about another, and why the useful question is not "how much" but "what exactly is included". We explain how a price is built in what waterproofing costs in Auckland. This page is the other half: how to read the quotes once you have them.
What to check on every quote
- Is it an overlay or a strip-out?
- An overlay goes on top of the existing membrane. A strip-out means removing it first, paying for disposal and leaving the building open until the new system is on. Two quotes for the same roof can differ by thousands on this alone, and the cheaper one is not always wrong. Ask which one you are looking at.
- Has substrate repair been priced, or assumed away?
- A membrane over soft or delaminated plywood fails with it. If one quote includes replacing sheets and another does not mention the substrate at all, they are not quoting the same job. The second one is not cheaper, it has just moved the cost to a variation later.
- What upstand heights and terminations are specified?
- This is where flat roofs actually leak. A quote that states termination heights at walls, door thresholds and parapets has been thought about. One that says "waterproof deck" has not.
- Is access and edge protection in the price?
- Scaffold, edge protection and safe access at height are legal requirements, not extras. If they are absent from a quote, either they were forgotten or they were never going to be provided.
- Which warranty comes with it?
- Workmanship warranty covers the installation. A manufacturer warranty covers the material, and it is only valid when an approved applicator installs to the manufacturer specification, which usually costs more in preparation and detailing. Both are useful. They are not the same thing, and only one of them survives if the company stops trading.
- Is the LBP number on the quote?
- Membrane roofing is restricted building work. It has to be carried out or supervised by a Licensed Building Practitioner with a roofing endorsement, and the number can be checked on the public register before you sign anything.
- What is listed under exclusions?
- Most unpleasant surprises live here, not in the scope. Scaffold, substrate replacement, removal of cladding or doors, drainage correction and council documentation are the usual ones. A quote with no exclusions section has not been thought through, it has been shortened.
Where the savings usually come from
When a quote lands well below the others, the difference is rarely efficiency. The shortcuts are consistent, and they all share one trait: none of them are visible on the day the job finishes.
- Primer skipped, so the membrane never fully bonds to the substrate
- Laps too narrow, or laps not offset between layers
- Upstands terminated low, usually because taking them higher meant removing cladding or a door
- Old membrane left in place when it should have come off
- Substrate repairs the roof obviously needs left out of the scope
- No scaffold or edge protection priced
- Installer not holding the LBP licence membrane roofing legally requires
These take two or three years to appear. By then the water has been in the framing for a while, and the remediation costs a multiple of what the shortcut saved. We cover the warning signs in how to spot a bad waterproofing job.
How our quotes are put together
We quote from an on-site inspection, never from a rate card. Every quote states the system specified, what is included, what is excluded, and which warranty applies to that scope. Where something cannot be known until the existing surface comes up, we say so in writing rather than absorbing a risk we cannot size.
The assessment is free and there is no obligation. If another quote comes in lower, we would rather explain the difference than quietly drop the specification to match it. More on what is covered in our warranty, and on credentials in how to check a contractor is certified.
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