Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application March Alan Baxter

Transcription

1 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application March 2016

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3 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application March 2016 Contents 1.0 Introduction Existing Structure Geology Proposed Structural Works... 5 Overall Proposals... 5 Refurbishment of existing Cremer Street Building... 5 Extension of Cremer Street Building... 6 Drainage... 7 Surveys... 8

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5 1.0 Introduction This report has been produced for the client, The Geffrye Musuem, by Ltd to provide structural engineering support to the planning submission by Wright and Wright architects for the refurbishment and extension of the Cremer Street building at the Geffrye Museum. The museum is situated in the London Borough of Hackney, on the east side of Kingsland Road adjacent to Hoxton Overground station and the Cremer street building is situated at the south-east corner of the site. The project involves creation of a new café and residential units through the refurbishment and extension of the existing building. KINGSLAND ROAD N C R E M E R S T R E E T BRANSON COATES BUILDING SOUTH WING EAST WING NORTH WING PUB CREMER ST BUILDING GEFFRYE STREET Keyplan Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March

6 2.0 Existing Structure Description The Cremer street building dates from around 1840 and was formerly a public house at the corner of terraced houses on Geffrye Street and Cremer Street. The building has 3 storeys including a basement. The structures comprises load bearing masonry walls and timber floors. The walls are founded on the Hackney Gravels see section 3.0. The south and west facades are framed at ground floor level with a series of cast iron columns supporting beams at 1st floor level. The bressummer beam that supports the first floor masonry elevation above the ground floor windows in the south façade is timber whilst the beam in the east façade has been replaced at some point and is formed from a pair of rolled steel joists. Internally, at ground floor level there are two cast iron columns that support the timber first floor structure. Condition There are currently artists occupying the building. Some parts of the structure are covered which means it is not possible to see the full extent of the existing defects. However, it is clear that the existing building is in poor condition. The south façade is in a particularly poor state. This is likely to be due to deterioration of the timber bressummer at first floor level which has led to movement and cracking of the masonry above. The overall stability of the building would originally have been provided in part by the adjacent terraced buildings. However, since the terraces have been removed the lateral stability of the building is not robust and the proposed scheme will need to address this. The roof is a much altered timber construction with a double valley arrangement running north to south behind a tall masonry parapet. Existing structure of Cremer Street Building 2 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March 2016

7 Short term stabilisation works Due to the poor condition of the building, a set of short term stabilisation works were implemented in February and March This involved installing braced timber frames to the facades to improve their in-plane stability and provide support to the deteriorating timber bressummer. Additional boarding and straps were also added to the floor of the pub to improve the restraint provided to be facades by the first floor. Key Plan Stabilisation works carried out in early 2016 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March

8 3.0 Geology The previous site investigations undertaken at the Museum provide a good understanding of the underlying ground conditions. Generally, these comprise of a layer of made ground over disturbed brickearth over sand and gravel over London Clay. According to local geological maps, the London Clay overlies the Lambeth beds and Thanet Sands over Chalk to a depth of over 150m. The brickearth layer is a soft yellow/brown silty sand with some gravel and clay, which varies in depth from 1.6m to 2.8m. The sand and gravel layer is very dense, yellow/brown, and becomes more sandy with depth. The local Geology map shows this layer is approximately 5.5m thick to the top of the London Clay, although this was not proven in the previous site investigations. Geological Sections of Site Trial pit undertaken inside Almshouses 4 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March 2016

9 4.0 Proposed Structural Works Overall Proposals The existing Cremer Street building is to be converted into a café making an important connection to the museum gardens and new main entrance. The proposals are to refurbish and extend the existing building to form a 4 storey mixed use building to include a café at ground floor level and 8 residential units in the upper floors. Refurbishment of existing Cremer Street Building The refurbishment of the existing building will include demolishing the low grade additions to the north of the original block, repairing the retained structure, and adding a storey on top through the formation of a new roof. The robustness of the facades will be enhanced with new posts installed and strengthening works undertaken to the existing timber bressummer beam. The repairs will also include consolidation of the masonry external walls and repairs to some areas of timber floor joists that have been affected by wet rot as identified in the timber survey. To assist with the overall stability issues noted in section 2.0 the building will be tied back to the new extension to buttress the buildings in the same manner as the terraced houses would originally have done. The new floor at second floor level will be formed with new steel beams sitting on the external walls and a new set of internal posts with timber joists. The roof structure will be formed in timber and be supported on lightweight timber stud walls supported on the second floor structure. Ground floor plan Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March

10 Extension to Cremer Street Building The existing building will be extended to the north and west to provide additional space for the residential units and café. The extension will be 4 storeys high and be formed as a reinforced concrete frame supported off of spread foundations founded at the same level as the existing building, ie on the Hackney Gravels. First floor plan (Second floor similar) Third floor plan 6 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March 2016

11 Drainage The foul and surface drainage in the building will be kept separate and combined at the boundary of the site before being connected to the main public sewer in Cremer Street. The drainage will not be taken down to the basement level and will run below the ground floor slab level to avoid the need to pump it. Surface water flows from the site will be restricted through the installation of an attenuation tank below the slab level of the new concrete frame to comply with the planning policy requirement to reduce both the volume and rate of existing run-off from site by at least 50% where reasonably practicable through the appropriate incorporation of SuDS. Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March

12 Surveys Timber Environmental Building Solutions Ltd (EBS) visited site in the latter half of 2015 to survey the building and have provided a report. The survey identified local issues with the timber joists suffering from wet rot and identified that the timber bressummer is also in poor condition. The findings of this report have been considered in the proposals for the building and low key repairs will be specified accordingly. Example timber survey sketches 8 Geffrye Museum - Cremer Street Building Structural Engineering notes to support planning application / March 2016

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14 Prepared by Olivier Fernandez Reviewed by Adam Sewell Issued March 2016 T:\0882\ \12 DTP Data\ _Cremer Street Planning Report_ \ _Cremer Street Planning Report_ indd This document is for the sole use of the person or organisation for whom it has been prepared under the terms of an invitation or appointment by such person or organisation. Unless and to the extent allowed for under the terms of such invitation or appointment this document should not be copied or used or relied upon in whole or in part by third parties for any purpose whatsoever. If this document has been issued as a report under the terms of an appointment by such person or organisation, it is valid only at the time of its production. Ltd does not accept liability for any loss or damage arising from unauthorised use of this document. If this document has been issued as a draft, it is issued solely for the purpose of client and/or team comment and must not be used for any other purpose without the written permission of Ltd. Ltd is a limited company registered in England and Wales, number Registered office: 75 Cowcross Street, London, EC1M 6EL. Copyright subsists in this document.

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