House Renovation Investigations

38 Bay View Discussion Paper: Demolition Extents Eastern Component of House Prepared by: Matthew Williams Date: 29 September 2020

Existing Condition – Levels The elements in question are shown at left. Levels are indicated on the Survey Plan obtained for 20 Bay View Street. It would be useful to obtain a complete survey for 38 Bay View Street. Levels are described as Relative Level (RL), which means a level relative to an Australian Height Datum setout point determined by the Surveyor.

Approximate Levels can be summarised as follows: • • • • • •

Foundation of Wall: Unknown Level of Living Floor: RL 23.80 Level Of Living Floor Balcony: RL 24.74 Level of Master Bedroom Floor: RL 27.3 Level of Master Bed Ceiling: RL 30.6 Level of External Gutter: RL 30.6

Window head and sill levels are marked on the survey at left and sketch below. Top of wall for the external perimeter wall above the garage is RL20.13.

This provides approximate clear heights as follows: • •

Living Floor, Floor to Ceiling: 3.2 metres Master Bedroom Floor, Floor to Ceiling: 3.05 metres

Clearance heights for these spaces are required to be a minimum of 2.7 metres, however houses in the premium residential market may be up to 3.6 metres or even 4 metres.

Clearance in the living exiting living area around the existing kitchen position is around 3.6 metres. It is noted that this space feels generous and spacious in height.

Existing Condition – Setout and General Arrangement Currently, the living room orients along the northern frontage of the house and opens into the Garden via a very generous full height glazed wall. It is likely that this large atria-like window was constructed at a time subsequent to the construction of the main house. This large opening appears to be supported by inbuilt steel frame.

Whilst this configuration provides very generous northern light into the main living space, it does not orient towards the main view for the house which is to the east and south east. This view affords dramatic and remarkable, unobstructed views of Lavender Bay, Luna Park, Sydney Harbour Bridge, the Opera House, Sydney City and Barangaroo. This is a globally iconic and very highly sought after view aspect.

At the eastern end of the living space, there are a total of 2 steps and 3 risers, where the living level rises up approximately 600 mm to form a zone designated ‘formal living’. Refer plan at left.

This space is then surround by an octagonal perimeter, with masonry walls and infill glazing. Glazing in this zone is not full height and is set above the floor and below the ceiling.

Continuing east and outside of this ‘formal living’ zone there is a deck, approx. 2 metres in width, wrapping the external perimeter of this octagonal façade.

Existing Condition – Foundation of Eastern Perimeter Wall We assume the top of the garage floor to be at approximately RL20. The sandstone wall at the base of the octagonal masonry wall is approximately 2 metres high. A footing can be seen at the base of the octagonal wall and at the same level approximately as the top of the sandstone retaining wall. This means that the base of the octagonal wall is at RL 22.0 approximately.

The proposed level of the new basement is RL 16.5, equivalent to street level outside the property (this is done to allow for gravity drainage to the street of any water that may gather in the basement). The new gallery floor level is proposed at RL 20.13. The existing living floor level is at RL 24.0.

The new Gallery Floor level is therefore relatively constrained by the Street Level and the existing living level above. The footing of the existing octagonal wall therefore conflicts with the proposed gallery level.

Existing Condition – Likely Wall Section and Roof Framing Arrangement Sketch at left shows what is considered to be the existing construction and assembly of the eastern octagonal wall component of the house.

Double skin masonry construction for the façade is founded on a strip footing. Timber joists spring from the top of the masonry wall to support the roof sheet, set on battens traversing the roof framing elements.

This construction technique is traditional for domestic home construction.

Construction Methodology for Retaining the Octagonal Wall Option 01: Gallery Level extent is constrained by Octagonal Wall Setout Windows are removed. Brickwork is cut above and below the window opening to allow for full height opening. Permanent steelwork is installed so brace the upstanding masonry levels and slab edges. Wall is temporarily propped during construction to ensure stability.

Option 02: Living Level floor is adjusted to match Main Living Floor Level Steel work and temporary propping as above. Once wall is braced, slab is demolished. Vertical steel columns constructed to take load from masonry wall, requiring footings at ground level. Formwork for new slab is built and new slab poured at desired level. Slab will not be contiguous with masonry wall. Temporary propping of formwork will be removed and new slab will load to new steel frame.

Option 03: Gallery Level constructed below octagonal wall Because of the conflict between the level of the existing footing supporting this wall and the gallery level, it is necessary to either extend the octagonal wall down to the new gallery level to connect with ground, or, if the gallery level will not follow the profile of the octagonal wall, steelwork supporting the masonry wall above.

Work will include as per option 2, including deep steel beams providing temporary and/or permanent support to the bottom of the existing masonry wall.