The wrong mortar can do more damage to heritage brickwork than the problem it was meant to fix. Older brick and sandstone buildings were built with lime mortar, and repointing them with a hard, modern cement mix — even one that looks right on the day — can accelerate the exact decay it was meant to prevent. Getting the mortar right matters as much as getting the joint looking neat.

The Problem With Modern Cement in Old Buildings

Older brick and sandstone buildings were originally built with lime mortar — softer, more flexible and more permeable than the Portland cement mixes commonly used today. Heritage NSW's mortars guide sets out why that difference matters: when cement-based mortar is used to repoint or repair older masonry, it is often harder and less permeable than the surrounding brick or stone, and that mismatch — not the mortar itself — is what causes the damage.

Why That Mismatch Causes Damage

Moisture that would normally evaporate through the mortar joints instead gets forced through the brick or stone itself, since the mortar is now the less permeable material in the wall. Over time this accelerates spalling, fretting and surface loss in the masonry — the very deterioration the repair was meant to prevent. Because cement mortar is also more rigid than lime, it can't accommodate the small amount of natural movement in an older wall, which shows up as cracking either in the joint or, worse, in the brick or stone next to it.

Repointing vs Tuckpointing: They're Not the Same Thing

The two terms get used interchangeably, but they describe different jobs. Repointing is a repair: removing failed, crumbling or eroded mortar and replacing it with new mortar to restore the wall's structural and weatherproofing performance. Tuckpointing is a decorative finish — a fine, often contrasting-coloured ridge of "tuck" pointing applied to a mortar joint to create the appearance of unusually fine, precise brickwork, a style common on Federation and Victorian facades. A wall can need repointing without ever having been tuckpointed, and tuckpointing without addressing failed mortar underneath doesn't solve a structural problem — it's worth being clear on which one a property actually needs before agreeing to a scope of work.

What Compatible Repointing Looks Like

  • Mortar matched in strength, permeability and flexibility to the original material, not just colour
  • Lime-based or lime-blended mixes for pre-20th-century masonry, in most cases
  • Joint profiles and tooling that match the building's original detailing
  • Removal of failed cement pointing carried out carefully, without damaging the brick or stone arrises
  • Attention to what's actually causing the mortar to fail in the first place — salt or moisture problems left untreated will just fail the new mortar again

Matching Isn't Just About Colour

A repointing job that looks right from the street but performs differently to the original mortar can still cause long-term damage. Getting the mix right — strength, permeability and finish — matters as much as getting the colour right, even though colour is what is most visible on the day the work is finished. Australia ICOMOS's Burra Charter, the national conservation standard, treats this kind of material compatibility as a core principle — not a finishing preference — precisely because the wrong material can undo the repair it was meant to be.

What a Proper Repointing Job Actually Involves

Repointing well takes longer than it looks. Failed mortar needs to be raked out to an adequate depth — not just skimmed over the surface — so the new mortar has enough of a key to bond properly. Lime-based mortars also cure differently to cement: they set through slow carbonation rather than a chemical reaction, which typically takes weeks rather than days, and freshly pointed lime work needs protecting from rain, frost and rapid drying during that period or the joint can fail before it's fully cured. On a larger or more visible facade, work is usually staged in sections so the wall isn't fully exposed at once and the finish can be checked and matched as it goes, rather than discovering a mismatch after the whole wall is done.

Heritage Listing and Council Approval

Repointing a heritage-listed building, or one inside a heritage conservation area, can need council approval — though many councils treat genuine like-for-like repair (matching the existing mortar, colour and joint profile) differently to other external works. The City of Sydney, for example, allows an exemption from development consent for certain heritage works — requirements vary by council, so it pays to confirm before work starts rather than after.

When to Have Existing Mortar Assessed

If a building has previously been repointed with cement and is now showing signs of brick or stone deterioration, it's worth having the mortar itself assessed as part of any repair plan — not just the visible damage. The same applies to a wall that's never been touched but has mortar joints that are soft, gapped, or crumbling by hand: that's usually a sign the original lime mortar has reached the end of its working life and needs replacing before the surrounding masonry starts to suffer for it.

Stoneline Heritage Restoration carries out assessment-led inspections for brick, mortar and repointing across Sydney and NSW. Request a site assessment and we'll check the mortar, not just the joint that's visibly failing.

Frequently Asked Questions

Can I repoint brickwork myself?

Small, non-structural cosmetic touch-ups are within reach for a confident DIYer, but repointing older or heritage brickwork is easy to get wrong in ways that aren't obvious until years later — the wrong mortar mix or joint profile can trap moisture and accelerate the exact damage repointing is meant to prevent. It's worth having it assessed even if you plan to do some of the work yourself.

How do I know if my house needs repointing?

The clearest signs are mortar you can scrape out with a finger or a key, visible gaps between brick and mortar, crumbling or powdery joints, and damp patches that track along the mortar lines rather than the brick face. A previous cement repointing job that's now cracking or staining the surrounding brick is also a strong signal.

Is tuckpointing the same as repointing?

No. Repointing repairs failed mortar; tuckpointing is a decorative ridge finish applied over a joint to create the look of fine, precise brickwork. A wall can need one without the other, so it's worth being clear on which problem you're actually trying to solve.

Why can cement mortar damage old brick or sandstone?

Because it's harder and less permeable than the original material. Moisture that should evaporate through the mortar instead gets pushed through the brick or stone face, and the mortar's added rigidity can't accommodate the small natural movement in an older wall — both accelerate cracking, fretting and surface loss.

Does repointing a heritage-listed building need council approval?

Often not for genuine like-for-like repointing, but it depends on the council and the exact scope — some require a heritage exemption or maintenance approval even for matching repairs. Check with the relevant council before starting.

Mortar is easy to overlook because it's not the star of the wall — but choosing the wrong one is one of the most common ways well-intentioned repairs end up causing the next round of damage.