How to match a rear extension to a 1920s Adelaide bungalow

Before drawings begin, agree the design intent with your designer. There are two defensible strategies for a rear extension to a 1920s bungalow and one indefensible one.

The first is a sympathetic match. The new addition uses similar materials, similar rooflines, similar window proportions, and reads as if the original bungalow had been built slightly larger from day one. This works well where the original bricks can be closely matched and where the block orientation supports a similar roof form.

The second is a confident contemporary counterpoint. The new addition is deliberately of its time: flat roof or low-pitch parapet, glazed rear wall, contrasting materials (charred timber, dark render, standing seam metal). The junction between old and new is clearly articulated so the eye reads two distinct eras that respect each other. This works particularly well on smaller blocks where a match would look cramped.

The indefensible strategy is a half-hearted attempt to match that misses on two or three details. Wrong roof pitch, wrong window proportions, close-but-not-quite bricks. This reads as trying and failing, and it damages the resale value of the home more than either of the disciplined strategies.

The classic 1920s Adelaide bungalow has a broad hipped Marseille tile roof at roughly 22 to 25 degrees. Any new rear extension roof at 15 degrees or below will read as separate. Any new roof at 30 degrees or above will visually dominate. If you are matching, match the pitch precisely, and use the same Marseille profile in a colour blend that reads together from the street.

If you are counterpointing, drop the roof pitch dramatically to a flat parapet at three to five degrees, and set the parapet back from the original eave line by at least 300mm. This creates a clean visual separation and gives the eye a rest between the two eras.

The one thing to avoid is a middle-ground pitch of 20 degrees on the addition against 25 degrees on the original. The eye reads this as an error rather than a design choice.

The bricks used in Adelaide bungalows of the 1920s came from a small number of suppliers, and most are no longer in production. Sourcing a close visual match is possible for common red bricks, but harder for the browns, cream stringers, and character clinker bricks used in the more distinguished bungalows of Toorak Gardens and Malvern.

Three practical strategies work. First, use a recovered brick supplier for the addition front-facing walls. Second, use a modern kiln-fired brick that reads close-but-different, with a bond-course string course band that visually separates old from new. Third, render both old and new the same colour, sacrificing the tuck-pointed detail in exchange for a clean modern envelope.

One thing to avoid: buying a modern red brick and hoping it will match. Modern kiln bricks have a different colour tone, surface texture and mortar profile from 1920s hand-fired bricks. In direct sunlight the mismatch reads immediately and only worsens as the new bricks weather.

A 1920s bungalow typically has raised suspended timber floors on stumps or short piers, with the finished floor level 400 to 600mm above ground. Modern extensions almost always use a concrete slab on ground. The transition detail matters both visually and practically.

The cleanest solution is to match the finished floor level exactly. The new slab is stepped down at the perimeter to allow the top of the slab to align with the existing timber floor above. The detail is well-understood, and any experienced Adelaide extension builder can execute it.

The compromise solution is a small step at the transition, typically 100 to 150mm. This is acceptable if the transition happens at a doorway with a shallow ramped threshold. The building consent will require the step to be marked with contrasting flooring and the door frame detailed for safety. If small children or older parents live in the home, a step is a hazard that will bite for decades.

The wrong solution is a large step of 300mm or more, which happens when the builder pours the slab at ground level without a step-down detail. Under standard building consent conditions this will not pass, but occasionally it does and then becomes a permanent tripping hazard.

The front verandah of a 1920s bungalow is often protected under a Character Area or Historic Area Overlay in inner Adelaide councils. The council rules typically prohibit removing, enclosing or materially altering the front verandah, including its posts, its balustrade if original, and its return along the side of the home.

A well-designed rear extension does not touch the front verandah, does not enclose the side verandah, and does not project past the ridgeline of the original roof when viewed from across the street. The addition should be effectively invisible from the front footpath.

If the block orientation is unusual (a corner block or a wide-fronted block), the side elevation may also be visible from the street. In that case the addition should either sit well behind the original side wall (typically two to three metres set back), or use materials and proportions that read as a considered extension rather than an afterthought.

Before design starts, walk across the street with a photograph of the existing home, and take another photograph from each neighbouring driveway. Any addition that would be visible from either of those sightlines needs to be handled with more care than a purely rear addition would.