Diagnosis before price
Why a waterproofing quotation follows the diagnosis, not the other way round.
Waterproofing is the one service where quoting before diagnosing is actively dishonest. Until the water's route is known, nobody can say what treating it involves.
Reviewed 6 September 2026.
At a glance
Why can waterproofing not be quoted over the phone?
Because the same visible symptom has several possible causes, and they need different work. A damp patch might come from a terrace joint, an external wall, a bathroom or a failed line. Until we know which, any price is a guess, and treating the wrong one costs you the whole job again.
Measured by treated area and by detail
The flat area receiving a system is only part of the quantity. Junctions, upstands, corners and penetrations take disproportionate labour and are where most waterproofing fails, so they are counted separately rather than absorbed into an area rate.
In order of impact
What moves the number.
Listed largest first. If a quotation is silent on the ones near the top, that silence is itself the answer.
What the diagnosis finds
The single largest variable, and the reason the inspection comes first.
How much has to be opened up
Reaching the source may mean removing finishes, and what is behind them is not always visible beforehand.
Drying time required
A wet substrate cannot be coated. Where drying is needed, the schedule lengthens.
System specified for the substrate and exposure
Different surfaces and exposures need genuinely different systems.
Extent of detail work
Junctions, outlets and upstands are slow and are where failures start.
Access and whether the area stays in use
A bathroom out of service or a terrace needing hoisted material changes the plan.
Method
How we build the quotation.
There are no figures here because none has been approved for publication. What follows is the sequence, so you can check anyone's quotation against it.
- Inspection of the affected area and every likely source above and outside it.
- A written diagnosis stating what we believe the source is — or that it needs opening up to confirm.
- Source treatment specified before any surface work.
- Drying allowed for, with the schedule reflecting it honestly.
- System and detail treatment specified for the substrate.
- Warranty conditions stated with their exclusions and maintenance obligations.
Waterproofing Cost Guide — your questions.
Can you give a rough idea before inspecting?
We can explain what the likely scenarios are and what each would involve, which is genuinely useful. What we will not do is give you a number for a cause we have not confirmed, because the wrong diagnosis makes the whole spend worthless.
Is waterproofing more expensive than painting?
Per square foot it usually is, because the preparation, the detail work and the materials are all more demanding. Comparing the two is not very useful though — they solve different problems, and paint over an untreated leak fails regardless of what it cost.
What if the source turns out to be in a neighbour's property?
It happens, particularly in apartments. We will identify it and explain it to you clearly, and to your neighbour or association if that helps. Treating it needs access to the source, which is a conversation we cannot have on your behalf.
A measured quotation costs nothing.
We measure the property, assess the surfaces and issue an itemised quotation you can hold us to. There is no charge and no obligation.
- We call you back the same day to get a picture of the property and the surfaces.
- We agree a time and come out for the free inspection.
- You get the written scope and itemised quotation.
- Nothing starts until you approve it.