When a renderer arrives at your property for the first time, don't expect to see plaster flying straight onto the walls. A professional renderer will spend a good portion of day one on preparation and assessment — because the quality of the finished surface depends almost entirely on what happens before the first trowel of render is applied.
The Initial Site Walk-Through
Your renderer will start by walking around the property with you to confirm the scope of work. They'll check the substrate (the surface being rendered), look for any cracks, moisture damage, or areas of concern, and confirm what system and finish you've agreed on. This is your chance to ask questions and flag anything you're unsure about.
If they spot issues — like rising damp, cracked or hollow existing render, or substrate movement — a good tradesperson will point these out before starting rather than rendering over problems that will cause failures later. Be prepared for an honest conversation if something unexpected turns up.
Setting Up and Protecting Your Property
Before any mixing begins, the renderer will set up their work area. You can expect to see:
- Drop sheets and masking applied to windows, doors, flashings, and any surfaces that shouldn't be coated
- Scaffolding or mobile towers erected if the work is above ground level (this may have been done the day before)
- Mixer and materials positioned close to the work area — bags of render, sand, cement, and any additives will be staged nearby
- Water supply confirmed — rendering uses a significant amount of water for mixing and cleaning tools
If scaffolding is involved, make sure access is clear and that vehicles or garden furniture are moved out of the way beforehand. WorkSafe NZ sets requirements for safe working at height, and your renderer should have this covered.
Substrate Preparation
This is often the most time-consuming part of day one. The renderer will prepare the surface so the render bonds correctly. Depending on your substrate, this may include:
- Cleaning the surface to remove dust, dirt, oil, or loose material
- Chipping or grinding off any hollow, delaminated, or failed existing render
- Applying a bonding agent or primer to improve adhesion, particularly on smooth or low-porosity surfaces
- Fixing mesh — on fibre cement sheet cladding (such as James Hardie products) or over control joints, fibreglass or alkaline-resistant (AR) mesh is embedded to control cracking
- Installing stop beads and corner beads — these metal or PVC profiles give the render clean, straight edges at corners, reveals, and termination points
The type of substrate matters enormously. Masonry, concrete block, brick, and fibre cement sheet all behave differently and may require different primers or systems. Your renderer should be working to the manufacturer's specifications for the product system they're using.
Mixing and Applying the First Coat
Once prep is complete, the renderer will mix and apply the scratch coat (also called the base coat or first coat). This is a relatively rough layer that:
- Builds up the thickness of the render system
- Is deliberately scratched or keyed while still wet so the next coat bonds to it
- Is left to cure before subsequent coats are applied — this could be anywhere from several hours to a couple of days depending on the product and weather
In NZ, render systems commonly use cement-based products, acrylic-modified renders, or proprietary systems. Products from suppliers like Sika and Ardex are widely used by professional renderers. Always check that the system being used is appropriate for your cladding type and complies with the NZ Building Code, particularly Clause E2 (External Moisture).
What the Weather Means for Day One
Rendering is weather-dependent. Your tradesperson will be keeping a close eye on conditions. Render should not be applied:
- In direct hot sun or strong wind, which causes it to dry too fast and crack
- In rain or when rain is forecast within the curing window
- In temperatures below about 5°C or above 35°C
If conditions aren't right, a professional renderer may delay the start or adjust their plan. This is normal and sensible — don't pressure them to push on in poor conditions.
What You Should Do on Day One
- Ensure clear access to all areas being rendered
- Move vehicles, outdoor furniture, and pot plants away from the work zone
- Keep children and pets away from the site
- Be available for a brief chat at the start, but then let them get on with it
- Don't water gardens close to the work area — wet ground can splash render
When to Call a Professional
Rendering is skilled trade work. While a homeowner can do minor patching on a garden wall, any rendering to an exterior cladding system on a habitable building is best left to an experienced renderer. Poorly applied render can lead to moisture ingress, which is one of the most costly defects in NZ homes. If your home is a weathertight repair or involves a monolithic cladding system, it's especially important to use a qualified tradesperson. You can find local renderers on tradedirectory.co.nz.
For work that requires a building consent — such as re-cladding or significant alterations — check with your local council first. Some work may qualify as a Schedule 1 exemption, but always confirm this before starting. MBIE Building Performance has guidance on when consent is required.
Licensed Building Practitioner (LBP)
