Retaining Walls in Bayview Heights

Bayview Heights climbs the slopes on the southern side of the city, and most of it was subdivided and cut in the seventies and eighties. The retaining that went in then is now forty or fifty years old, which is why so much of the work here is replacement rather than new construction.

What that generation of walls looks like

The walls of that era are predominantly timber: hardwood or treated sleepers with timber posts, built at a time when the treatment standards, the drainage expectations and the approval requirements were all different from today’s.

They have done well to last this long. What we find now is fairly consistent. The posts have failed at ground line, which is where timber posts always go, because that is the zone with both moisture and oxygen. The sleepers themselves are frequently still sound while the posts holding them are not, which produces a wall that leans as a unit rather than bulging. Termite damage is common, and in this region unsurprising.

The other consistent finding is that many of them were built without any drainage layer at all. That was not necessarily negligence at the time; it was ordinary practice. It does mean these walls have spent decades under a load nobody designed for, which is part of why they are going now.

Replacing rather than repairing

When a timber wall of that age has gone at the posts, repair is generally not the honest answer. Replacing individual posts on a wall whose remaining posts are the same age and in the same condition buys a couple of seasons.

The replacement conversation is usually about material. A concrete sleeper wall with galvanised posts removes both failure modes that killed the original, and on a wall that would otherwise be replaced again in twenty years, that is straightforward arithmetic rather than an upsell.

Fill from the original subdivision

The other thing worth knowing about this area is that a lot of the flat ground is fill placed during the original earthworks. Fill of that era was not always placed and compacted to the standards used now, and its behaviour under a new wall’s footings cannot be assumed.

It matters because a new wall’s footings need to bear on something reliable. Where the ground under a proposed footing is uncontrolled fill, the footing either goes deeper to reach competent material or the design accounts for what is actually there. Finding that out during excavation rather than assuming it is part of doing the job properly.

Staging the work

Where a property has a long run of original wall, replacing all of it at once is often not affordable and not necessary. Walls fail in sections, and staging the replacement by condition rather than doing the whole run is a reasonable approach as long as the sequence makes sense structurally.

Ring 0468 066 055 and we will tell you which sections are actually urgent.