Sinnamon Park is a younger suburb on the river side of Seventeen Mile Rocks Road, named after the Sinnamon family, who farmed the district for more than 100 years from the 1860s. Part of their farm, at 645 and 693 Seventeen Mile Rocks Road, is on the Queensland Heritage Register. Housing estates were built from the 1980s, and the number of houses doubled between 1991 and 2004.
Estate walls from day one
Unlike the older Centenary suburbs, where owners added walls over the years, many Sinnamon Park lots were shaped by the developer before the house went up, first in the Jennings estate of the 1980s and later in the Windermere estate near the river. Builders cut the high side and filled the low side to make a level pad, and retaining walls along side and rear boundaries were often part of the subdivision works. That has two consequences. First, those walls may have been designed and approved as part of the estate, so there may be engineering records worth finding. Second, many are now twenty-plus years old, and timber walls of that age are reaching the end of their life.
Small lots, tight setbacks
On compact lots, walls are rarely far from a house. A wall closer than 1.5 m to a building, yours or the neighbour's, is outside the exemption from building approval in Building Regulation 2021, Schedule 1, regardless of height. So even a short replacement wall along a side boundary often needs a certifier. Brisbane's City Plan also has specific rules for houses on small lots, and Brisbane City Council's retaining wall page notes that walls associated with a dwelling house on a small lot may need planning approval.
Replacing without undermining
When an estate wall is replaced, the builder has to hold the ground on both sides while the old wall comes out, especially where a fence, a slab or the neighbour's yard sits right behind it. Good builders will stage the work in short sections and may install new posts before removing old sleepers. Ask how they plan to do it.
River and overland flow
In the January 2011 flood, water in Sinnamon Park mostly followed the open-space floodways along the river and barely touched nearby houses. Flood and overland-flow mapping still varies from street to street. Check the council's City Plan online mapping and FloodWise Property Report for your address. A wall must not block an overland flow path or push water onto another lot.
Heavy soils
Former farm flats along this stretch of the river can have clay or silty soils. Soils vary from block to block, so your builder or engineer should check yours. Wet clay and silt hold water and push hard on walls when saturated. Gravel backfill, ag pipe and a clear outlet matter more than the face material you choose.
Useful things to find before a quote
- Your house plans or estate documents, which may show the original wall design.
- Whether the wall is shared with a neighbour.
- Any signs of movement: gaps between sleepers, leaning posts, cracked fence footings.
Sinnamon Park questions
My estate wall is only 20 years old. Why is it failing?
Timber estate walls often used treated pine that can rot at ground level within 15–25 years, faster in wet clay with poor drainage. Concrete sleepers or block with proper drainage last much longer.
Is a wall near my house exempt from approval if it's short?
No. In Queensland a wall closer than 1.5 m to a building is outside the exemption, regardless of height. On compact Sinnamon Park lots that applies to many side-boundary walls.
Want a price for your wall?
Send the suburb, a rough length and height, and what the wall holds up. A licensed builder can then contact you to arrange a quote.