Braddon Office Block

The building

This three-storey office building in Braddon has a large concrete roof deck housing air-conditioning plant and a lift overrun. The original membrane had been patched several times, and after a wet spring two tenancies on the top floor reported ceiling stains and drips over workstations.

The property manager needed a long-term fix that would not disrupt the businesses operating below.

Assessing the roof

We surveyed the roof after rain and mapped where water was sitting. Around a third of the deck held water for days at a time, mostly in areas that were far from the two existing outlets. The membrane had blistered across these areas, and several laps had opened up around the plant plinths.

Core samples showed the old membrane was not well bonded, so an overlay was not suitable. It needed to come off.

Planning around tenants

Working on an occupied commercial building takes planning. We agreed a schedule with the property manager that kept the noisiest stripping work to early mornings and moved crane lifts outside peak traffic times on Lonsdale Street. Each section was stripped and sealed with a temporary layer on the same day, so the building was never exposed overnight.

The new system

Once the old membrane was removed, we:

• built up sand and cement screeds to create falls toward new drainage points
• installed two additional sumps with overflow outlets through the parapet
• laid a base sheet and cap sheet torch-on membrane across the full 640 m²
• reinforced every upstand, plinth and penetration with extra layers.

A section-by-section flood test confirmed the membrane and new drainage were performing before handover.

Handover

The building manager received photos of key details, product and warranty information and a simple maintenance schedule focused on keeping outlets clear. Since completion, the top-floor tenants have reported no further leaks.