How to Match New Mortar Colour to Your Existing Brickwork

Matching new mortar to existing brickwork is one of the trickier aspects of DIY brick repair — get it wrong and the patch will stand out like a sore thumb. The good news is that with careful preparation, a few test batches, and the right materials, you can achieve a result that blends in well. Here's what you need to know.

Why Mortar Colour Is So Hard to Match

Fresh mortar almost always looks different from aged mortar. Over time, mortar weathers, fades, and picks up dirt and mineral deposits that give it a unique tone. The original mix ratio, cement type, sand colour, and any pigments used all affect the final colour — and those details are rarely recorded. This means matching is always a process of trial and error, not an exact science.

NZ brickwork also varies widely by region. The sand used in Auckland, Wellington, or Christchurch can differ significantly in colour, which directly affects mortar tone. Always source your sand locally where possible.

Step 1 — Analyse Your Existing Mortar

Before you buy anything, take a close look at your existing mortar joints:

• Colour: Is it grey, cream, buff, brown, or off-white?
• Texture: Is it smooth and dense, or coarse and sandy?
• Joint profile: Is it flush, recessed (raked), or rounded (ironed)?

Scrape a small amount of old mortar from a hidden spot and crumble it between your fingers. This gives you a rough idea of the sand-to-cement ratio — a very sandy, crumbly mix suggests a weaker, sandier mortar, while a harder mix indicates more cement.

If you're unsure of the original mix, a common general-purpose mortar for NZ brickwork is 1 part cement : 1 part lime : 6 parts sand (by volume). Older homes may have used a lime-only mortar with no Portland cement at all — important to know, as using a strong cement mix on soft old bricks can cause damage.

Step 2 — Choose the Right Sand

Sand is the single biggest factor in mortar colour. Cement and lime are both grey-white, so the sand largely determines the final tone. Common options available from NZ builders' merchants include:

• Yellow or golden sand — warm buff tones
• White or off-white sand — pale, light mortar
• Grey river sand — cooler, mid-grey tones
• Brown or red sand — earthy, warm tones

Visit your local PlaceMakers or Mitre 10 and compare sand samples against your existing mortar in natural daylight.

Step 3 — Use Mortar Pigments

If sand alone doesn't get you close enough, mortar pigments (also called oxide pigments) can fine-tune the colour. These are iron oxide powders available in colours like red, yellow, brown, black, and buff. Add them to your dry mix before adding water.

Key tips for using pigments:

• Use no more than 10% pigment by weight of cement — too much weakens the mortar.
• Measure carefully and record your ratios so you can replicate the mix.
• Pigments are available from Bunnings and specialist masonry suppliers.
• Some suppliers offer pre-blended coloured mortar mixes, which can simplify the process.

Step 4 — Mix and Test Small Batches

Never apply your first attempt straight to the wall. Instead:

1. Mix a small test batch using your chosen sand, cement, lime, and pigment ratios.
2. Apply it to a spare brick or a piece of board.
3. Allow it to fully cure for at least 48–72 hours — mortar lightens significantly as it dries.
4. Compare the cured sample to your existing mortar in natural daylight (not indoors under artificial light).
5. Adjust your mix and repeat until you're satisfied.

Keep a written record of every batch — ratios, pigment amounts, and water quantity — so you can reproduce the winning mix consistently.

Step 5 — Consistent Mixing and Application

Once you've nailed the colour, consistency is everything:

• Always use the same proportions for every batch. Variations in water content or mixing time can shift the colour.
• Use a bucket and measuring scoop rather than eyeballing quantities.
• Mix to the same consistency each time — mortar that's too wet will be weaker and may dry lighter.
• Match the joint profile of the existing mortar. A raked joint looks very different from a flush or rounded one, even if the colour is identical.

Realistic Expectations

Even a well-matched mortar repair will be noticeable up close when it's fresh. Over 6–12 months of weathering, the colour difference typically reduces significantly. In NZ's variable climate — particularly in wetter regions — biological growth (moss, lichen) also plays a role in how mortar ages. A perfect invisible match is rarely achievable, but a close match is very much within reach.

For guidance on mortar mixes and their suitability for different NZ conditions, BRANZ publishes technical resources that are worth consulting.

When to Call a Professional

Matching mortar is a skill that improves with experience. Consider hiring a qualified bricklayer if:

• The area to be repointed is large (repointing an entire wall or façade).
• Your home is older (pre-1960s) and may have lime-only mortar — using the wrong mix can damage soft bricks.
• The brickwork is structural or load-bearing.
• You're unsure whether the work requires a building consent — always check with your local council, as some repairs may fall under Schedule 1 exemptions but others may not. See MBIE Building Performance for guidance.

A licensed bricklayer will have experience matching mortar across many different NZ brick types and can often achieve a far better result than a first-time DIYer. You can find qualified local bricklayers on tradedirectory.co.nz.

Sources & Further Reading

• BRANZ — Building Research Association of NZ
• MBIE Building Performance — Building Code & Consents
• Bunnings NZ — Mortar & Masonry Products
• PlaceMakers NZ — Building Materials
• Mitre 10 NZ — Masonry & Concrete
• Standards NZ — NZS 3604 and related standards