Questions to Ask a Waterproofer Before You Hire Them

Why it pays to ask detailed questions

Waterproofing is one of those jobs where a small mistake can turn into a very expensive problem later. Leaks can damage framing, linings, flooring, insulation and neighbouring properties, and the repair bill is often much higher than the original job.

That is why the first conversation with a waterproofer should be more than a quick price check. You want to find out whether they understand the job, work to NZ standards, can coordinate with your builder or plumber if needed, and will stand behind their work.

A good rule for New Zealand homeowners is to get at least two or three written quotes, and to compare more than just the final price. The right questions can help you choose a tradesperson who is competent, properly insured and realistic about timeframes.

Ask about their experience with your type of project

Not all waterproofing jobs are the same. A waterproofer who mainly works on commercial membrane systems may not be the best fit for a small tiled bathroom renovation, and vice versa.

Ask:

• What types of waterproofing do you do most often?
• Have you done jobs like mine before?
• Do you work on bathrooms, laundries, showers, balconies, decks or wet rooms?
• Are you experienced with the membrane system or product I want to use?
• Can you show photos of recent similar projects?

If your job involves a bathroom in an older NZ home, ask whether they have experience dealing with uneven substrates, timber flooring, existing water damage or ventilation issues. In many homes, especially older villas and bungalows, the underlying structure may need extra attention before the membrane goes on.

Also ask who will actually do the work. If the person quoting is not the person on site, ask about the team’s qualifications and who supervises the job.

Check whether the work needs other trades or approvals

Waterproofing often sits in the middle of a bigger renovation. Before you hire, ask how the waterproofer coordinates with other trades and whether any related work needs a licensed professional or consent.

Useful questions include:

• Will you work with my builder, tiler, plumber or bathroom installer?
• Do any parts of the job involve plumbing, gasfitting or drainlaying that must be done by a person authorised under the Plumbers, Gasfitters and Drainlayers Board (PGDB)?
• Is there any electrical work nearby that needs to be done by a registered electrician under the Electrical Workers Registration Board (EWRB) rules?
• Does this project need building consent from my local council?
• Will you tell me if you find issues that must be fixed before waterproofing can start?

As a general rule, waterproofing itself may not always require building consent, but related bathroom alterations sometimes do, especially where structural changes, new wet areas, or significant plumbing changes are involved. The safest approach is to confirm with your council or designer before work starts.

Ask what products and system they will use

The quality of the waterproofing system matters as much as the installer’s skill. A professional should be able to explain what product they recommend and why it suits your situation.

Ask:

• What waterproofing system will you use?
• Is it suitable for this room and surface?
• Is the product compliant with NZ requirements and the manufacturer’s instructions?
• How many coats or layers will be applied?
• How long does it need to cure before tiling or use?
• What preparation is needed before you begin?

A good waterproofer should be able to explain whether the job needs a sheet membrane, liquid membrane, floor and wall treatment, or a system designed for specific substrates. If you have a shower, tiled bathroom, laundry or balcony, the product should suit the exposure and movement expected in that area.

Be wary of anyone who is vague about the system, says they use a product “all the time” but cannot name it, or suggests skipping preparation to save time. Surface preparation is a major part of waterproofing success.

Confirm their credentials and training

New Zealand does not have one simple licence that covers every waterproofing job in every situation, so it is important to ask what training and evidence they can provide.

Ask:

• What training or qualifications do you have for waterproofing?
• Are you certified by the membrane manufacturer or trained in their installation system?
• Do you follow the relevant NZ standards and manufacturer specifications?
• Can you provide evidence of your business registration or trade membership, if applicable?
• Are your workers trained in the specific product you will be using?

If the job is part of a larger renovation, ask whether they understand the building code requirements relevant to wet areas. In NZ, quality waterproofing is usually expected to align with accepted building practice and the manufacturer’s instructions. You are not just buying labour; you are paying for a system to be installed correctly.

Ask about insurance and workmanship cover

Insurance is easy to overlook until something goes wrong. For waterproofing work, it is worth asking directly what cover the company has and what protections you get if defects appear later.

Ask:

• Do you have public liability insurance?
• Do you have contract works insurance, if relevant?
• Are you insured for damage caused by installation faults or accidental leaks?
• What workmanship guarantee do you provide?
• Is the guarantee written, and what does it cover?
• What happens if a problem appears after completion?

A solid answer should be specific. For example, they should be able to explain whether the guarantee covers the membrane itself, the installation labour, or both, and for how long. Also ask whether you need to maintain the area in a certain way to keep the guarantee valid.

If a waterproofer says they are “covered” but cannot explain the policy type, limits or exclusions, keep asking questions. A cheap quote is not much use if a leak leads to a dispute and nobody is properly insured.

Get a quote that spells out the scope

Quotes vary a lot in NZ, especially if your bathroom needs demolition, substrate repairs or urgent scheduling. A useful quote should make it clear what is included and what is not.

Ask:

• Can you provide a written quote?
• What exactly is included in the price?
• Does the quote cover preparation, primer, membrane, labour, cleanup and GST?
• Are substrate repairs, sealants, corners, drains or movement joints included?
• What are the likely extras or variations?
• What could cause the price to change?

Here is a simple comparison checklist you can use when reviewing quotes:

If one quote is much lower than the others, ask why. It may exclude important steps, use a cheaper system, or assume the substrate is perfect when it is not. In waterproofing, the lowest price is not always the best value.

Discuss timelines, weather and programme constraints

Timing matters, particularly in NZ where renovation work often has to fit around school holidays, peak summer demand and wet winter weather.

Ask:

• When can you start?
• How long will the waterproofing portion take?
• How long do you need for surface prep, drying and curing?
• What happens if the weather delays outdoor work?
• How will your schedule fit with the tiler, builder or plumber?

If your job includes an outdoor balcony, deck or exterior membrane, ask how wet weather will affect the programme. In many parts of New Zealand, winter moisture and cooler temperatures can slow drying times and affect application windows. A realistic tradesperson will factor that in rather than rushing the job.

You should also ask when the area will be ready to use. Some membranes may be touch-dry quickly but still need a longer curing period before tiling, grouting, or exposure to water.

Ask how they handle quality control and sign-off

A professional should have a process for checking their own work before leaving site. That process matters because waterproofing faults are often hidden once the room is finished.

Ask:

• How do you inspect the substrate before starting?
• Do you take photos during the work?
• How do you check thickness, coverage or detailing around corners and penetrations?
• Will you provide completion photos or product records?
• Do you issue any sign-off or compliance documentation where relevant?

For bathroom or wet-area work, ask how they manage critical details such as:

• shower hob or low-threshold entries
• floor waste and drain detailing
• wall and floor junctions
• pipe penetrations
• corners and transitions to other materials
• sealant and termination points

If the waterproofer cannot explain how they prevent weak points in these areas, that is a warning sign.

Ask for references and recent local work

References are useful because they show whether the waterproofer is reliable, communicates well and finishes on time.

Ask:

• Can you give me two or three recent customer references?
• Have you completed similar work in my area?
• Can I see photos of finished jobs?
• Are there reviews I can check from recent clients?

When you speak to references, ask about more than workmanship. Find out whether the tradesperson arrived when promised, kept the site tidy, communicated clearly and dealt with any issues professionally.

Local experience is especially useful in NZ because housing stock varies so much between regions. A waterproofer working on apartments in Auckland may face different access and compliance issues from someone working on rural homes, older properties in Wellington, or holiday houses that need exterior waterproofing for harsh coastal conditions.

Watch for red flags before you sign

A good tradesperson will usually welcome careful questions. Be cautious if you notice any of these warning signs:

• they refuse to give a written quote
• they cannot explain the product or process
• they promise an unrealistically fast turnaround
• they discourage you from checking references
• they cannot explain insurance or guarantees
• they say consent or compliance does not matter when you suspect it might
• they pressure you to pay a large deposit before any details are confirmed

You should also be wary of anyone who suggests waterproofing is a simple coating job that does not require proper preparation. The hidden work is often where quality is won or lost.

A simple checklist to use before hiring

Before you make your decision, make sure you can answer these questions with confidence:

• Have they done similar jobs before?
• Do they understand NZ standards and manufacturer requirements?
• Are they insured?
• Is the quote written and detailed?
• Are timelines realistic for your site and season?
• Is the guarantee clear and in writing?
• Have you checked references?
• Do you know whether any other licensed trades or council approvals are needed?

If you can tick those boxes, you are in a much better position to hire a waterproofer who will do the job properly the first time.

The right questions do not just protect your budget. They help protect your home from leaks, delays and avoidable rework.