Heritage Stonework — Woollahra
A Federation-era sandstone chimney in the Eastern Suburbs rebuilt from the flashing up. Case study: matched sandstone, hand-dressed courses, and rebuild finished without lifting roof tiles.
What was wrong when we arrived
The chimney had been patched three times with cement mortar over the previous twenty years. The cement had trapped moisture, the top courses had spalled, and the chimney pot was sitting on a bed of crumbly sandstone.
A roof plumber had refused to do the flashing replacement until the chimney was sound. The owners could not get any other trade to quote the rebuild — most roofers do not do stonework, and most masons do not do roof work.
The owners did not want to lose the original chimney pot. It was a rare late-Victorian Sydney-make and finding a match would have been near-impossible.
How we fixed it
Two of us on the roof. The chimney was taken down from the flashing up — about nine courses. The original pot was lifted down on a rope and set aside on padded boards on the lawn.
Five of the original sandstone blocks were sound and went back in. The remaining four were replaced with hand-dressed Hawkesbury sandstone, cut on site to match the original coursing and the original rough-faced texture on the front elevation.
Mortar was a 1:1:6 lime-putty, brickies sand and crushed Sydney sandstone mix, matched on the existing wall for colour. The chimney was struck off flush with the original profile.
The pot was re-bedded on a fresh lime bed and the flashing was done by the roof plumber the next morning. No roof tiles were lifted.
What the client got
The owners kept the original chimney pot. The roof plumber has used us for two more chimney rebuilds in the area since.
No water ingress in the two wet seasons since. The chimney is weathertight and the lime mortar is curing properly — it has gone paler and harder, not darker and softer.
The rebuild matches the original sandstone closely enough that the neighbour walked past for a month before noticing.
Questions about heritage stonework
Can a sandstone chimney be repaired, or does it need to be completely rebuilt?
It depends on how far the damage has gone. If only the top three or four courses are spalled and the rest of the chimney is sound, a partial rebuild from the flashing up is usually the right call. If the chimney is leaning or the mortar has failed all the way down, it comes down further. We assess in person and tell you what is actually wrong, not what is easiest for us to quote.
How do you match the original sandstone?
We take a sample of the original stone and source from the same kind of quarry. Most Sydney sandstone is Hawkesbury or Pyrmont, both still quarried in small batches. For older buildings we sometimes have to use a reclaim yard. The match is rarely perfect on day one, but it fades in within a season of weather.
How long does a chimney rebuild take?
Most chimney rebuilds are one to two weeks on the roof, plus the roofer coming in for flashing after. We give you the schedule before we start so the roofer can be booked in for the right day.
Have a job like this one?
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