RPE ENGINEERING SERVICES MECHANICAL & STRUCTURAL CONSULTING ENGINEERS

7 Edgewater Dr PO Box 5161

DIAMOND BEACH NSW 2430 HALLIDAYS POINT NSW 2430

Phone: (02) 6559 3400 Mobile: 0428 653 578

Fax: (02) 6559 3411 Email: rpes@bigpond.net.au

G.C. Venn-Brown FIEAust CPEng - Principal

21 March, 2014 ref. 14037.r01A

Wes Zuber & Corinne Fuller c/- Australian Hotel 24 Bent Street WINGHAM NSW 2429

ENGINEERING REPORT

Timber-framed building at 24 Bent Street, Wingham

Background:

The subject building, known as the ‘Heritage Stables’ was erected some 120 years ago on the western part of the site occupied by the existing Australian Hotel, in Wingham.

The building is timber-framed with a corrugated iron roof. It has mostly open sides, and the roof structure is supported on large diameter (approximately 300 – 400 mm) hardwood posts. The building has considerable heritage value, since it is probably the last of its type and size in the region.

The building suffered some damage during a wind storm that occurred on the afternoon of Sunday 16 March, 2014. As a result, building contractor Wayne Munro of Waylyn Homes was called in to inspect the damage. Mr. Munro was concerned about a number of aspects of the condition of the structure, and he called in RPE Engineering Services, consulting structural engineers, to examine the building.

Chris Venn-Brown FIEAust CPEng inspected the building on 21 March, 2014, in the company of Wayne Munro, his assistant, Ian Grey, and the Licensees of the Australian Hotel, Wes Zuber and Corinne Fuller.

Discussion:

The inspection revealed a number of major faults. There is clear evidence that some of these occurred during the wind storm. However, many of them pre-existed the storm.

There has not been an opportunity to carry out detailed calculations, but observation of the dimensions and arrangements of structural members suggests that it is unlikely that the structure, in its as-built state, would have complied with current Australian Standards.

In its inadequate state, it is not surprising that a number of local structural failures have occurred over the years. Repairs and other modifications have been made, but generally these appear to have been carried out without any reference to a structural engineer, or to an experienced builder or carpenter. As a result most of the repairs and modifications are of poor quality.

Again, because of its existing inadequacies, the building was vulnerable to damage during the recent wind storm. Such damage occurred, and the building is now even more vulnerable to future storms. The following photographs illustrate many (but not all of) the existing structural problems.

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Photo 1: Shows the uneven roof-line. The steel beam (in yellow) is buckled laterally towards the camera.

Photo 2: All of the timber tie-beams are sagging significantly, showing that they are (or have been) over-stressed. A new timber beam has been added to strengthen an existing tie beam,

but it is under-sized.

Photo 3: Another view of sagging members

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Photo 4: Lateral buckling in steel beam (see Photo 1) Photo 5: Roof strut connection dislodged during storm.

Photo 6: Rafter broken during storm. Photo 7: Poor pre-existing connection details

Photo 8: Poorly designed steel bracket which connects to sections of a tie-beam, supports roof struts, and is fixed to a longitudinal beam (which is twisting under the load applied by the bracket).

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Photo 9: Inadequate connections with nails pulling out. Photo 10: Roof sheeting rusted through in many places

Photo 11: The northern end of the building was rebuilt a few years ago, and is in better condition.

The timber posts which provide the support for the building (some of which are visible in Photos 3 and 11) are generally in satisfactory condition, although an individual detailed inspection is recommended if the posts are to remain in use.

The greatest risk with a structure of this type is that during high winds the air pressure beneath the roof will increase, while the normal effect of a wind blowing across such a roof is to cause negative pressures above the roof. This is exacerbated when some of the sides are effectively blocked by adjacent buildings (as in this case). The positive pressure beneath the roof, combined with the negative pressure above it may cause the roof to lift off its supports and be transported laterally until it falls to the ground, where it almost certainly will cause damage to other structures and/or death or injury to passers-by.

Individual roof sheets, a larger section of the roof, or the roof as a whole, could perform this way.

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There is a lesser, but still significant, risk that the structure could collapse inwards. In this case the potential for damage and death or injury would be confined to a smaller area, but still exists.

Lastly, an LPG gas pipe runs from LPG cylinders on the ground on the western side of the structure, to the hotel, attached to a roof tie beam. It is located on the part of the roof that was repaired a few years ago (see Photo 11), but if the older section of the structure were to fail, there remains a significant risk of damage to the pipe and even possibly the cylinders, which could lead to an LPG explosion or fire.

Rectification:

As nearly all of the roof sheeting and a large proportion of the timber and steel structural members in the building require repair or replacement, rectification of the building to make it safe and to bring it into line (at least in principle) with current standards is not considered to be a practical proposition.

To carry out the work, the existing roof sheeting would need to be removed to allow access to its supporting structures. Taking into account occupational health and standards requirements, the precarious condition of the structure precludes workers from walking on the roof,. Therefore, removal of the sheeting would be to be done remotely, and would be an extremely costly exercise.

Furthermore, there is some danger to workers beneath the roof, especially during the dismantling process. The existing structure (obviously) has some capacity to hold itself up, but if individual members are removed, the overall strength of the structure will be degraded, and the risk of collapse will increase.

Following removal of the sheeting, a significant proportion of the timber members would require replacement, and the rectified building would incorporate a high percentage of new timbers and sheeting.

Notwithstanding the heritage value of the building, it would appear that the cost of rectification would be unreasonably high..

It is therefore recommended that the bulding be demolished.

Due to the significant risk of failure in the next wind storm, it is recommended that demolition be carried out as a matter of urgency.

Note:

The owners may choose, however, to retain the timber posts in position, as these posts potentially could be used as part of the structure of a building that may be erected on the site in the future. The posts on their own should not pose any threat of damage or injury to others, but, following demolition of the roof structure which they are supporting, they should be checked by a structural engineer to confirm that this is the case.

Summary and Conclusions:

The 120 year old Heritage Stables on the site of the Australian Hotel, Wingham, were examined, following a wind storm that occurred on Sunday 16 March, 2014.

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The examination revealed that in the ‘as-built’ condition, it is unlikely that the structure of the stables would comply with current Australian Standards. Repairs to isolated failures over the years, and other modifications, are generally of poor quality. The building suffered further damage during the wind storm, and is now extremely vulnerable to further failures or collapse should a similar storm occur.

Rectification of the building does not appear to be a viable option, due to the extent of the repairs required, and due to the difficulty of undertaking the repairs safely.

Only the main supporting timber posts could sensibly retained for incorporation into a future building to be erected on the site.

It is therefore recommended that the building be demolished, as a matter of urgency.

The owners may choose to retain the main supporting posts (subject to a detailed inspection by a structural engineer), should they so desire.

G.C. Venn-Brown F.I.E.Aust. CPEng. RPE ENGINEERING SERVICES

Staff Report S1 - Attachment (v)