STRUCTURAL REVIEW OF CALDWELL HOUSE

129-133 SALE STREETORANGE, NSW

JOB NO. 35086

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 2 of 19 June 2018

TABLE OF CONTENTS

1.0 Introduction 3

2.0 Notes from inspection of building 4

3.0 Review of original building plans 4

3.1 Structural capacity of existing slab 4

3.2 Fire resistance period (FRP) for existing slab 4

4.0 Partial demolition of structure 6

4.1 Partial demolition – Option 1 6

4.2 Partial demolition – Option 2 6

4.3 Partial demolition – Option 3 6

5.0 Discussion 7

6.0 Conclusion 8

Appendix A Plans of original construction 9

Appendix B Preliminary sketch plans for partial demolition 16

Document Ref: 35086-5Revision Description Prepared Verified Issue DateA Draft Issue DOC 27.06.18B Issue for Approval DOC DOC 02.07.18

COOK AND ROE

Daniel CookBE MIEAust

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 3 of 19 June 2018

1.0 INTRODUCTION

Cook and Roe have been engaged to prepare a structural review of the existing building known as Caldwell House, located at 129-133 Sale Street, Orange. This review has been undertaken based on an inspection of the building by Mr. Daniel Cook, senior structural engineer for Cook and Roe, on 16 April 2018, along with a review of the available plans for the building. The building in question is a two storey building of full brick construction with a timber framed ground floor, concrete first floor and a timber framed roof with terracotta tiles over. The original building was constructed in 1937, with additions to the western end of the building constructed in 1944.

We note that the inspection undertaken was visual only; no destructive or invasive investigation techniques were adopted. Whilst every effort was made to inspect all surfaces, the inspection was limited by the presence of floor and wall coverings and plastic sheeting covering asbestos effected areas that could not be reasonably moved during the time of the inspection.

Figure 1 – Subject Site, 129-133 Sale Street, Orange

CALDWELL HOUSE

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 4 of 19 June 2018

2.0 NOTES FROM INSPECTION OF BUILDING

As noted previously in this report, the inspection of the structure was limited due to the asbestos present in the building and the subsequent concealment of the asbestos material. The following items were noted at the time of inspection:

Generally the building was found to be in sound structural condition, with no major damage evident to the brick walls, concrete and timber floor structures, or roof structure of the building;

All internal brick walls to the building are load-bearing; Some minor modifications to the structure have been made, which include the enclosing of the first

floor balcony and the demolition of a number of first floor external walls that adjoin the balcony.

3.0 REVIEW OF ORIGINAL BUILDING PLANS

The original building plans for Caldwell House were obtained from Health Infrastructure NSW and a review of these plans was undertaken in order to ascertain the structural capacity of the building, and to determine the fire-rating capacity of the concrete floor elements. Our review of the plans noted the following:

The first floor concrete slabs are generally noted as 4½” thick (115mm); Reinforcement has been laid with a specified cover of ¾” (19mm) to the soffit; Main reinforcing bars are typically ⅜” (9.5mm) diameter, spaced at centres ranging from 4” to 7”

(115mm to 178mm); Slabs have typically been design as one-way slabs, although the plans confirm that all existing

masonry walls below the first floor are load-bearing.

Plans for the original 1937 construction are attached in Appendix A of this report.

3.1 Structural Capacity of Existing Slab

Based on the reinforcing and slab thicknesses outlined in the documentation for the original section of the building a structural analysis was undertaken in order to assess the structural capacity of the first floor slab. Based on available historical information for materials used around the time of construction, a yield strength of 230 MPa has been adopted for the steel reinforcing bar and a compressive strength of 20 MPa adopted for the concrete.

The structural review undertaken indicates that the existing floor slabs generally meet the strength requirements for loading under residential design loads. The deflections calculated in the concrete floor slabs under these loads, particularly the eastern balcony slab, exceed current recommended serviceability limits.

Any increase in floor loading above residential type activities would potentially overstress the existing slab and create additional, and likely excessive, deflections in the slab in a number of areas.

3.2 Fire Resistance Period (FRP) for Existing Slab

Section 5.5 of Australian Standard AS 3600 Concrete Structures addresses Fire Resistance Periods (FRPs) for concrete slabs. An FRP is made up of fire resistance periods for structural adequacy, integrity and insulation expressed in that order. These values represent time, in minutes, for a member to reach the appropriate failure criterion (i.e., structural adequacy, integrity and/or insulation). Clause 5.3.1 of AS 3600 states that a member shall be designed to have a fire resistance period (FRP) for structural adequacy, integrity and insulation of not less than the required fire resistance level (FRL). If applicable, the criteria for integrity shall

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 5 of 19 June 2018

be considered to be satisfied if the member meets the criteria for both insulation and structural adequacy for that period.

The FRP for insulation for slabs is specified in Table 5.5.1 of AS 3600, shown below. Based on the slab thicknesses noted in Section 3.0 of this report the FRP for insulation would be 90 minutes.

The FRP for structural adequacy for slabs supported on beams or walls is specified in Table 5.5.2(A) of AS 3600, shown below. Based on the cover to reinforcing noted in Section 3.0 of this report the Axis distance to the lowest layer of reinforcement would be 24mm. On this basis the majority of the first floor slabs would have an FRP for structural adequacy of 120 minutes as they are continuous slabs, however the balcony slab on the Sale Street side of the building has been reinforced as a one way slab, and hence would only achieve an FRP for structural adequacy of 90 minutes.

Based on the above review the first floor concrete slabs achieve FRPs of either 120/90/90 or 90/90/90. On this basis the slab has the capacity to achieve a Fire Resistance Level (FRL) of 90 minutes. For any FRL greater than this value additional fire protection of the slab would be required.

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 6 of 19 June 2018

4.0 PARTIAL DEMOLITION OF THE STRUCTURE

Part of the structural assessment of the building includes a review of a number of options to retain the façade of the structure, allowing the remainder of the building to be demolished and rebuilt to suit potential occupant requirements. Three different options were considered for the partial demolition:

Option 1 – Retention of eastern (Sale Street) façade and awning with partial retention of first floor; Option 2 – Retention of eastern (Sale Street) façade, awning and main roof; Option 3 – Retention of eastern (Sale Street) façade and awning only.

Each of the three partial demolition options has considered that the western section of the building is fully demolished, and only parts of the eastern wing, running parallel to Sale Street, are retained. Preliminary sections detailing the proposed three options are attached in Appendix B of this report.

4.1 Partial Demolition – Option 1

The first option considered for the partial demolition of the building is based on the retention of the front (eastern) façade to Sale Street, with minimal structural strengthening works carried out on the existing building. This option would consist of the following:

Removal of all roof tiles (for possible re-use) and removal of all timber roof framing; Complete removal of the western wall of the building; Complete removal of the ground floor timber framing; Removal of the wall on the eastern side of the hallway running north-south above first floor level; Complete removal of the wall on the western side of the hallway running north-south; Partial demolition of the first floor slab from the eastern side of the hallway to the west; Retention of the wall on the eastern side of the hallway, running north-south, from ground level to

underside of first floor; Retention of first floor slab from the eastern side of the hallway back towards Sale Street; Sections of the existing walls running east-west (perpendicular to the Sale Street façade) will be

required to be retained to provide stabilisation to the external wall of the building.

4.2 Partial Demolition – Option 2

The second option considered for the partial demolition of the building is based on the retention of the front (eastern) façade to Sale Street, and the roof of the structure. This option would consist of the following:

Complete removal of the ground floor timber framing; Retention of all walls running north-south in the building, including the western wall and the walls

either side of the internal hallway; Sections of the existing walls running east-west (perpendicular to the Sale Street façade) will be

required to be retained to provide stabilisation to the external walls of the building.

4.3 Partial Demolition – Option 3

The third option considered for the partial demolition of the building is based on the retention of the front (eastern) façade to Sale Street, with the complete demolition of all internal structure. This option would consist of the following:

Removal of all roof tiles (for possible re-use) and removal of all timber roof framing; Installation of a steel support frame consisting of wall columns, wall headers, struts and dead man

piers to allow for the complete demolition of the internal walls. We note that a significant portion

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 7 of 19 June 2018

of the existing structure would have to remain in place whilst the steel support frame is being installed in order to maintain stability of the façade.

Complete removal of the external walls of the building; Complete removal of the internal walls above the first floor slab; Propping of the existing balcony slab; Demolition of the first floor slab from the balcony back to the west. In order to provide a positive

connection to the potential new structure the slab should be saw cut to a nominal depth of 20mm and the remainder broken out in order to maintain the existing reinforcing in the slab and engage the new structure;

Complete removal al all internal walls to ground level.

5.0 DISCUSSION

The structural inspection of Caldwell House, along with the review of the original plans for the building identified that in its current arrangement the building structure is performing well. The main issues with the structure moving forward are the limited flexibility available in any proposed redevelopment of the building, and the significant presence of asbestos within the building, and what effects the required clean-up will have on the structure.

At present the building is made up of predominantly 9’ x 11’ (2.74m x 3.35m) dormitory rooms, with all masonry walls load-bearing in some form. We note that the NSW Land & Housing Corporation (LAHC) requires a minimum room dimension of 3.0m to meet its deemed to satisfy solution as outlined in the LAHC Design Standards – 2014 (Revision 1). On this basis it is anticipated that any future re-use of the structure would require some, and quite likely substantial, removal of these internal walls. In order to do this significant structure would be required to support the existing roof and concrete first floor where walls are removed. Given the likelihood that any re-use of the building would fall into Type A construction in accordance with the National Construction Code (NCC) any new supporting structure would have to be suitably fire rated.

The assessment of the structural capacity of the existing first floor slab found that the floor in its current arrangement is structurally adequate for residential loads. The arrangement of reinforcing in the slab is such that the removal of any wall would require additional support structure (i.e. steel beam or the like) to ensure ongoing stability. If the premises were to be ustilised for commercial activities that exceed residential loads, then strengthening of the floor slab would be required. Given the current arrangement of reinforcing in the slabs, simply installing additional steel support beams to reduce the slab span would not be feasible as this would induce cracking in the top surface of the slab. We anticipate that a new concrete floor slab would have to be constructed should strengthening be required for commercial activities.

Due to the significant amount of asbestos present within the building it is anticipated that a clean-up of the structure would require some modifications to the building, including some partial wall demolition and the pouring of a concrete ‘sealing’ slab over the contaminated sub-floor ground. The construction of this sub-floor slab would almost certainly require the removal of most, if not all, of the existing timber-framed ground floor structure.

Given the likelihood of a reasonable extent of demolition being required in the clean-up, and potential re-purposing of the structure, the partial demolition options outlined in Section 4 of this report were explored. This was undertaken in order to ascertain the most cost effective means of retaining the façade of Caldwell house whilst allowing the required cleanup to occur and providing flexible options for the re-use of the site.

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 8 of 19 June 2018

Given the high pitch of the roof, a large part of the façade retention revolves around the roof structure as this accounts for almost one third of the visible façade in terms of height. Option 2 for the partial demolition retains the roof structure, but given the construction of the existing building this requires the retention of almost all walls within the building; consequently this is not seem as a viable partial demolition option.

Both options 1 and 3 involve the removal of the roof structure, with the roof tiles retained for possible re-use. Option 1 utilises sections of the existing internal walls and floor to brace the front, eastern wall of the building. This option, whilst providing some flexibility, still retains a substantial amount of structure that would limit any potential re-use of the building.

Option 3 provides the most comprehensive removal of internal walls and floors, whilst maintaining the façade of the building. The installation of a temporary steel support frame allows for all internal walls to be demolished, with only the eastern wall of the building retained. This option provides the most flexibility of the three partial demolition options explored provided that the existing floor levels are maintained. This option does however require the complex installation of the steel support frame prior to the full demolition of the internal walls and floors.

6.0 CONCLUSION

The structural review of Caldwell House identified that the existing building, in its current arrangement, is performing adequately. The issues arise when considering the potential re-use of the building, and the clean-up of the asbestos material that is currently present throughout the entire structure.

Re-use of the existing structure as it currently stands is limited by the small room size, which is less than that required under the deemed to satisfy solution outlined in the LAHC Design Standards for affordable and community housing. In addition to this any potential commercial use of the building is limited by the strength of the existing first floor slab.

As identified in Section 5 of this report, it is highly likely that a partial demolition option will be required in order to adequately clean-up the building and allow for a flexible re-use of the structure. It is our opinion that the existing roof would have to be removed in any partial demolition scenario. In order to provide a building suitable for flexible re-use it is clear that Option 3 provides the most suitable partial demolition sequence; however given the complexity of the installation it is our opinion this methodology would be cost prohibitive, particularly when considered in conjunction with the clean-up of the site associated with the asbestos present within the building.

In summation, it is our opinion that there are only two options likely to be financially viable for any prospective purchaser of the site located at 129-133 Sale Street. These options are:

Adopting a re-use of the Caldwell House building that allows for little, if any modification to the existing structure, which would significantly limit the potential re-use applications, and;

Complete demolition of the Caldwell House structure, allowing for an unimpeded re-development of the site within Council planning policies.

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 9 of 19 June 2018

APPENDIX A

Plans of Original Construction

Structural Review of Caldwell House 129-133 Sale Street, OrangeJob No. 35086 Page 16 of 19 June 2018

APPENDIX B

Preliminary Sketch Plans for Partial Demolition