GAUTENG DEPARTMENT OF INFRUSTRUCTURE DEVELOPMENT

Transcription

1 GAUTENG DEPARTMENT OF INFRUSTRUCTURE DEVELOPMENT BUILDING ASSESSMENT REPORT STRUCTURAL FOR 75 FOX STREET AUGUST 2014 i P a g e

2 Table of Contents 1. INTRODUCTION Design Criteria and Specifications Scope of the Services Scheme Report STRUCTURAL ASSESSMENT Building configuration and interfaces with adjacent buildings Façade Roof Waterproofing and Roof Structures General Structural Floor Slab Assessment Structural Column and Concrete Wall Assessment Foundations Basement and Basement Retaining Walls Building Internal Brickwork Building Internal Finishes and Services Staircases Structural Floor Loading Allowances Allowed For Future Use PHOTOGRAPHIC EVIDENCE AND COMMENTS. 7 ii P a g e

3 1. INTRODUCTION The project brief, as issued by Gauteng Funding Agency (GFA), was to conduct an initial assessment of the building condition, services, structural integrity of 75 Fox Street, and to provide recommendations regarding the repairs and renovations of the buildings. 75 Fox Street is an occupied and functional building. The building has a structurally sound building frame and suffers only from minor detailing errors, water entry problems and internal and external service leaks. The building itself is in excellent condition, but requires the local details repaired to ensure that it stays in a good condition for years to come. The major maintenance items include the replacement of skylights and possible internal staircase corrections. The condition of the structural components is described below. Design Criteria and Specifications This project will be implemented in compliance with all the requirements of the National Building Regulations and the new SANS10400, including any town planning prescripts of the local authority. Scope of the Services Scheme Report This report deals with the proposed structural services to be implemented and preliminary design for the feasibility for the repairs and renovations of the existing buildings. 2. STRUCTURAL ASSESSMENT 2.1 Building configuration and interfaces with adjacent buildings 75 Fox Street building comprises 14 floors, 3 basements below ground, ground floor slab, 9 Floors and a roof slab system with local level differences. The building has a partial concrete roofs at level 14 and portions of the 13 th floor is external (roof area). The building has a number of feature balconies and gardens on the northern and southern facades at various slab levels. 75 Fox Street has no links to adjacent buildings. 2.2 Facade The existing façade comprises a marble cladding on a structural steel sub-frame fixed onto the concrete structural frame. The marble cladding is in excellent condition; however the renewal of the polyurethane joint sealer between the panels is required. In two local positions (above the southern parking entrance) the cladding panels will need to be re-adjusted. On the northern façade a missing cladding tile needs to be replaced. Aluminium windows are included in the façade and are in excellent condition. The window rubbers between the glazing and the frame have perished in certain locations on the north and eastern facades and need to be replaced. 3

4 The facade parapets are covered with steel panel sheet flashing. These panel junctions need to be resealed. The steel sheets have been blown off in a number of locations and require replacement and joint resealing. The vertical walls above roof level are in need of maintenance (painting) to avoid future damage of facades and occupancy below roof level. It is suggested that the external pavements around the building are lifted, levelled and re-laid as the trees and other damage has caused the walking surface to become uneven and is a tripping hazard in certain areas. A window cleaning system exists for cleaning the exterior windows. The rail system is in good condition; however the mechanical components must be checked by the mechanical engineers. 2.3 Roof Waterproofing and Roof Structures The flat concrete roof system consists of a stepped roof arrangement over 3 floor levels. The roof system has occupied floor areas, entertainment area, plant and general roof areas. There is no plant visible on the roof as it is housed in dedicated covered areas. The roof is generally covered in a varied size stone aggregate layer, underlain by a damp proof membrane covering the roof waterproofing. The roof appears to be waterproofed with a combination of acrylic roof sealant and torch on waterproofing in respective areas. The majority of areas have recently been recoated in acrylic sealant and is in excellent condition. There have been reports of water leaks under the new waterproofing in local areas, hence local repairs of the waterproofing should be allowed for. Allow 10% of the roof area for such repairs. Under the waterproofing is a screed to fall to fulbore outlets and associate downpipes. The screed and downpipes are in good working order. The following concerns need to be addressed with regard to the roof coverings: 1. The stone aggregate layer was not washed when installed and hence there is a layer of fine material above the waterproofing which has the potential for clodding rainwater goods and keeping the waterproof surface damp. 2. The stone layer stone size is too small and is being washed into the downpipes and possibly damaging the downpipes internally in the process and leaking to blockages down the line. 3. The presence of a damp proof membrane above the waterproofing in certain areas traps water on the waterproofed surface and hence increases the risk of leaking. 4. Loose laid external pavers require edge restraint to prevent edge breakage. 5. Tiled external areas and skirtings need to be locally repaired and resealed to eliminate water penetration into the structure. 6. External entrance door to the western fire escape should be covered with a weatherproof awning. 7. Central skylight to be refurbished/replaced. 8. Central skylight louvres orientation to be corrected to direct storm water outside the building. 9. Sloping skylight adjacent to the central skylight must be resealed. 4

5 10. Entertainment area soft roof requires a gutter system on its lower end to avoid rain water falling onto the incorrectly orientated louvres of the central skylight. 11. Roof façade walls which are plastered and painted are to be repainted 12. Façade render to be corrected and repaired locally where identified. 13. Safety hooks on the roof need to be replaced with more recent technology fasteners to comply with latest safety standards. There is a roof cleaning system with complete structural steel track system. The track system will require repainting, and the lifting system will require mechanical and electrical check. All structural steel elements on the roof require de-rusting and repainting. 2.4 General Structural Floor Slab Assessment In general the existing concrete slab structures are in excellent condition. The coffer slab construction of the floors from ground up and the flat slab construction of the basements are all in excellent conditions. No remedial works are required on the main floor slabs except for the following local issues: 1. Movement joint treatments to be addressed. In the parking slab situation the edges of the movement joints are chipping and degrading as there is no edge protection. The use of a steel plate secured on the one side of the movement joint is recommended, or a suitable architectural joint treatment that can accommodate 20mm structural movement. In the office ceiling situation, the plaster render must be treated with a cover strip consistently secured on one side of the joint to cover the joint in the render to architects details. 2. Replacing of the main southern entrance ramp (ground floor) mentis grating and the cleaning out of the drainage channel. 3. Replacing of a local portion of screed, centrally on the south façade of basement 1 is required. 2.5 Structural Column and Concrete Wall Assessment The building is supported by concrete columns and concrete core walls which are in excellent condition. 2.6 Foundations The building shows no signs of settlement and hence foundations and bearing strata below are in good condition. 2.7 Basement and Basement Retaining Walls The building has three sub-terrainian basements. The basements are in excellent condition except for the following local defects: 1. Water leak from surface ponding through the basement 1 slab to basement 2 below on the central southern façade. The replacement of the screed on basement 1 will solve the problem. 2. Local patches of horizontal water entry through the basement walls. The solution is to solve the leaking water pipe in Commissioner Street on the adjacent property, as well as applying local negative waterproofing in local areas. Allow 50m2 of negative waterproofing. 5

6 The basement as two sump pumps which have recently been replaced and are in excellent condition. 2.8 Building Internal Brickwork The building s internal brick walls are in excellent condition. There are a number of internal walls with superficial cracking, but these can be filled with polyfiller (or similar) and repainted as required. In the basement archive, there is a portion of plaster that is peeling off the walls due to a water leak. Details are in the photo evidence. 2.9 Building Internal Finishes and Services The building internal finishes and services are in good condition. Refer to architects report in this regard Staircases The building has three concrete internal circulation staircases and two structural steel fire escape stairs, one internal and one external. The internal concrete stairs are structurally sound and the handrail and surface finish are in excellent condition. The internal structural steel fire escape staircase is in excellent condition; however the stair geometry as built is does not meet current building regulations. The stair length is thread is too short and the stair inclination appears excessive. It is recommended that this stair is reconfigured for easier and safer use. The external steel fire escape is in good condition, but will require local de rusting and a complete repaint. For the staircase compliance with new SANS regulations refer to the fire engineer report Structural Floor Loading Allowances Allowed For Future Use Office and reception areas: 350kg/m 2 (Office occupancy + light weight partitions) Parking: 200kg/m 2 (Car parking (no trucks)) Roof Slabs 350kg/m 2. All new mechanical plant is best accommodated in existing plant rooms. Plant Rooms (All floors): 500kg/m 2. Note no masonry brickwork partitions are allowed internally and externally, unless verified by structural engineer. In general walls which are required to be masonry (that is bathrooms and kitchens) already exist. 6

7 3. PHOTOGRAPHIC EVIDENCE AND COMMENTS Figure 1: Northern façade of 75 Fox Street are in excellent condition. The jointing on the building will need to be resealed and the window rubbers renewed locally where required. Figure 2: Southern façade of 75 Fox Street is in excellent condition. The jointing on the building will need to be resealed and window rubbers renewed locally where required. 7

8 Figure 3: Eastern façade of 75 Fox Street is in excellent condition. The jointing on the building will need to be resealed and window rubbers renewed locally where required. Figure 4: Typical roof slab constructed from coffer slabs, with a screed to fall, waterproofing, damp proof membrane and varied size stone chip layer as a finish. 8

9 Figure 5: Roof stone chip layer is maximum 30mm thick and was not washed when installed. The result is a layer of fines on the waterproofing which will retain moisture and contribute to clogging of rainwater drainage paths and roof leaks. Figure 6: External roof tiling tile grout has been placed on a Damp proof membrane. This is a structurally acceptable detail; however the tiles should be secured on the edges of the tiled areas to avoid the paving surface breaking out at the edges. 9

10 Figure 7: A Damp proof membrane is placed over the waterproofing under tiling and stone chips this plastic sheet will retain moisture between the sheet and the waterproofing causing leaks. The use of a nonwoven geotextile is preferred as the fabric is porous and can dry out, and offers better protection to the waterproofing from human traffic above. In addition the stone chip size is too small and can easily be washed into the rainwater downpipes causing damage to the pipes. Figure 8: South eastern corner of the building showing well maintained roof. A maintenance schedule and local patching may be required. It is noted that the roof waterproofing is a mixture of torch on waterproofing and an acrylic based waterproofing product. It is suggested that one system is standardised and used throughout for future maintenance. 10

11 Figure 9: Mechanical plant air exhausts are present on the roof. It is noted that the mentis grids have locally sagged and it is recommended that he existing panel is simply reversed. There is moss growth on certain panels, best removed with a high pressure washer. Figure 10: Façade and window washing rails are present on the building and are in good working order. Now remedial works are required on this system, although the cleaning mechanism was not inspected on site, this may require maintenance and a check by the mechanical engineer that it complies with new safety regulations. It is recommended that the rails are repainted. 11

12 Figure 11: The acrylic based waterproofing present is in excellent condition, however local patching may be required as numerous leaks need may have been reported within the building. The building movement joints should also be checked for water tightness and correct detailing. Figure 12: Perimeter parapet wall flashings are installed in sections. The junctions require resealing with a flexible product to architects specifications. 12

13 Figure 13: A number of parapet flashings have been blown off and will require re-securing and re-sealing (of the junctions) with a flexible product to architects specifications. Figure 14: Safety hooks around the building will need to be replaced with newer technology to comply with new health and safety regulations and best practice. 13

14 Figure 15: The building southern façade and roof at roof level looking east. The building has a central skylight system that requires major refurbishment and resealing due to reported leaks. There are local smaller sloped skylights that are in good condition, but should be resealed to ensure that future leaks are prevented. Figure 16: View of the South western corner of the roof system looking west. All facades are in good condition; however the junction between the cladding panels will require resealing. The central roof skylight will require major refurbishment due to constant leaks. 14

15 Figure 17: Roof over the entertainment area directs roof water directly onto the central skylight and into the vertical glass louvres under the skylight eaves. A gutter and downpipes is recommended on this roof edge. Figure 18: Central Skylight louvres are orientated incorrectly and direct rainwater into the building instead of out of the building. It is recommended that the louvres are rotated so that the lower edges face towards the outside of the building. 15

16 Figure 19: Pipework on the western façade of the skylight hinders the functioning of louvres. It is suggested that the pipework is moved to allow proper functioning of the louvre system. Figure 20: Broken glass louvre panels as well as the incorrect orientation of the louvres are the cause of a substantial water entry into the building. 16

17 Figure 21: Central skylight system over central internal atrium showing defects in the skylight panels. The skylight requires a major refurbishment. Figure 22: Central skylight system over central internal atrium showing defects in the skylight panels. The skylight requires a major refurbishment. 17

18 Figure 23: Central skylight system over central internal atrium showing defects in the skylight panels. The skylight requires a major refurbishment. The skylight panels are seen to be waving, which is a cause of water leaks. Figure 24: The central skylight has a structural steel sub frame which is side fixed to the concrete below. It is noted that a number of the structural steel frames have loose anchor bolts at their fixity points. The bolts must be tightened and re-secured and measures put in place to ensure the bolts don t work loose over time (eg tack welding the nuts to the base plate one tightened. 18

19 Figure 25: Mechanical plant air exhausts are present on the roof. It is noted that the mentis grids have locally sagged and it is recommended that he existing panel is simply reversed. There is moss growth on certain panels, best removed with a high pressure washer. Figure 26: Access stairs and cat ladders require de-rusting and repainting. Note the incorrectly oriented louvres on the central skylight directing storm water into the building. 19

20 Figure 27: Service vent pipes require waterproof vent caps, re-rusting and repainting. Figure 28: Roof torch on waterproofing on Northern face (centrally) into fulbore outlets. The storm water system and waterproofing is in excellent condition, however the stone chips are too small and are flowing down the downpipes and causing internal damage. 20

21 Figure 29: External steel access stairways will require de-rusting and repainting. Figure 30: External tiling to northern entertainment terrace on the roof: The vertical tiled skirting is breaking away from the wall and allowing water entry behind the tile and causing vertical damp on the inside of the wall. 21

22 Figure 31: Roof slab above eastern fire escape stair has been recently waterproofed. This area appears to be the part of the roof where the rubbish collects. This area must be maintained or the rubbish will block the rainwater downpipes. Figure 32: Door to the Eastern fire escape stair requires a local small canopy over the door to prevent water entry into the building. The door frame also requires repair due to forced entry into the stairwell. 22

23 Figure 33: Typical façade panels: The panels themselves and substructure are in excellent condition. The grout between the panels is in excellent condition; however the polyurethane or similar sealant over the grout has degraded and is peeling off. The existing sealant should be stripped off and new sealant applied. Figure 34: Typical façade panels: The panels themselves and substructure are in excellent condition. The grout between the panels is in excellent condition; however the polyurethane or similar sealant over the grout has degraded and is peeling off. The existing sealant should be stripped off and new sealant applied. 23

24 Figure 34: Typical façade panels: The panels themselves and substructure are in excellent condition. The grout between the panels is in excellent condition; however the polyurethane or similar sealant over the grout has degraded and is peeling off. The existing sealant should be stripped off and new sealant applied. Figure 35: Curved Northern high level façade tiling is secured to a curved masonry/concrete beam: These tiles are at risk of coming loose if the surfaces of the support structure are not re-waterproofed on top and painted on the rear faces. 24

25 Figure 36: Curved Northern high level façade tiling is secured to a curved masonry/concrete beam: These tiles are at risk of coming loose if the surfaces of the support structure are not re-waterproofed on top and painted on the rear faces. Figure 37: The underside of the curved northern façade feature beam requires drip details and repainting. 25

26 Figure 38: The only vertical façade panel that has dislodged and fallen from the façade is on the north face on the eastern side. The panel appears to have slipped out of its securing brackets for unknown reasons. This panel will need to be replaced. Figure 39: The only vertical façade panel that has dislodged and fallen from the façade is on the north face on the eastern side. The panel appears to have slipped out of its securing brackets for unknown reasons. This panel will need to be replaced. 26

27 Figure 40: Above the southern entrance there are 4 misaligned vertical façade panels due to a vehicular impact on the panelling above the entrance. These local panels to be realignment and re-secured. Figure 41: Soffits of roof slabs show the resultant damage from previous leaks and need to be skimmed and repainted. 27

28 Figure 42: Marmoran type wall render is peeling off the walls on the southern façade of the roof walls from water ingress. The wall should be suitably patched and re-rendered. Figure 43: Façade flower box gardens are included in the building north and south facades. These gardens are irrigated and appear to be functioning well. It is suggested that the vegetation is replaced as certain plants appear to have grown too big for their environment and may have substantial root systems which will affect the waterproofing systems. Architectural guidance to be given in this regard. 28

29 Figure 44: Façade flower box gardens are included in the building north and south facades. These gardens are irrigated and appear to be functioning well. It is suggested that the vegetation is replaced as certain plants appear to have grown too big for there environment and may have substantial root systems which will affect the waterproofing systems. Architectural guidance to be given in this regard. Figure 45: A rusted structural steel element is present above the windows and sliding doors on the landscaped boxer boxes. This structural steel element will need to be replaced where required, preferably with a new galvanised element. This appears to be a local issue on the southern façade only. 29

30 Figure 46: In local areas the window rubbers between the glazing and aluminium frame has deteriorated and will need to be replaced. This is noted as local issues on the north and west facades of the building. Figure 47: Resultant damage to soffits of roof slabs where roof waterproofing had previously failed. The roof waterproofing has been recently maintained above. The areas above the affected areas to be rechecked for leaks prior to scrapping, skimming and repainted the slab soffits as required. 30

31 Figure 48: Resultant damage to soffits of roof slabs where roof waterproofing had previously failed. The roof waterproofing has been recently maintained above. The areas above the affected areas to be rechecked for leaks prior to scrapping, skimming and repainted the slab soffits as required. It is noted in addition that the finish around the light fittings is being damaged from the heat of the light fitting in constant operation. Figure 49: Resultant damage to ceilings where roof waterproofing had previously failed. The roof waterproofing as been recently maintained above. The areas of waterproofing above the affected areas to be rechecked for leaks prior to scrapping, skimming and repainted the slab soffits as required. It is noted in addition that the finish around the light fittings is being damaged from the heat of the light fitting in constant operation. 31

32 Figure 50: Lift motor rooms are in excellent condition, however resultant damage from roof waterproofing leaks is evident on the roof slab soffit. Roof waterproofing to be checked for leaks and soffit repainted. Figure 51: Lift motor rooms are in excellent condition, however resultant damage from roof waterproofing leaks is evident on the roof slab soffit. Roof waterproofing to be checked for leaks and soffit repainted. 32

33 Figure 52: Aerial view of the internal central atrium. The slab systems are coffer slabs with edge flower beds constructed as up stand beams. The structure is in excellent condition. Figure 53: Typical coffer slab construction of the office floor slabs from ground floor upward, all in excellent well maintained condition. 33

34 Figure 54: Typical ramp between basements in excellent condition. The grooved surface is a good feature for increased tyre grip. Figure 55: Typical flat soffit of the ramp system in excellent condition. 34

35 Figure 56: Rendered slab soffits within the occupied office spaces did not include provision of a joint in the finish under the slab movement joint. Hence the slab soffit finish has cracked in these locations. It is recommended that a detail is developed by the architect to hide these cracks (non-structural), such as a cover strip consistently secured to the one face of the joint only. Figure 57: Rendered slab soffits within the occupied office spaces did not include provision of joint of the slab movement joint above. Hence the slab soffit finish has cracked in these locations. It is recommended that a detail is developed by the architect to hide these cracks (non-structural), such as a cover strip consistently secured to the one face of the joint only. 35

36 Figure 58: Concrete Internal staircases within the building are in excellent condition both in finish and structurally. Figure 59: Concrete Internal staircases within the building are in excellent condition both in finish and structurally. 36

37 Figure 60: The eastern internal steel fire escape stair is in good condition, however the riser geometry makes climbing the stairs difficult. The stairs treads are too short. The minimum tread length should be 275mm. It is recommended that these staircases are reconfigured to make their use more comfortable and safe. Figure 61: The eastern internal steel fire escape stair is in good condition, however the riser geometry makes climbing the stairs difficult. The stairs treads are too short. The minimum tread length should be 275mm. It is recommended that these staircases are reconfigured to make their use more comfortable and safe. 37

38 Figure 62: Basement sump pumps in the lowest basement have been recently replaced and are in good working order. The pipe system which was previously leaking has been rerouted and is working well. Figure 63: Various inspection eyes for the subsoil drainage system are present and are in good condition. 38

39 Figure 64: Basement suspended slabs and surface beds are all in excellent condition Figure 65: Basement suspended slabs and surface beds are all in excellent condition 39

40 Figure 66: Local horizontal water entry is present on the south basement wall. This will need to be addressed with a waterproofing product applied to the internal face to architect specifications. Figure 67: Vertical water leak through the slab system is present in basement 2. This appears to a leaking from pooling water above (service leak or other) above in basement 1 which has caused this issue. The leaking service (if applicable) above to be repaired and the resultant damage repaired. 40

41 Figure 68: Vertical water leak through the slab system is present in basement 2. This appears to a leaking service above in basement 1 which has caused this issue. The leaking service above to be repaired and the parking surface screed repaired to restore the waterproof surface. Figure 69: The building has a movement joints in the north south direction. A noticeable lack of detailing of this joint within the building is noticeable both in the vertical and horizontal planes. The joint must be covered with vertical cover strips secured on one side of the joint only in an architecturally selected material. 41

42 Figure 70: The building has a movement joints in the north south direction. A noticeable lack of detailing of this joint within the building is noticeable both in the vertical and horizontal planes. The horizontal joint in the parkade to be covered by a steel plate secured on one face of the movement joint to detail. Figure 71: The building has a movement joints in the north south direction. A noticeable lack of detailing of this joint within the building is noticeable both in the vertical and horizontal planes. The mailing room column joint must be covered with vertical cover strips secured on one side of the joint only in an architecturally selected material. 42

43 Figure 72: Southern basement parking entrance ramp in good condition, however the mentis storm water grid half way up the ramp must be replaced and the channel below it cleaned out. Figure 73: Southern basement parking entrance ramp in good condition, however the mentis storm water grid half way up the ramp must be replaced and the channel below it cleaned out. 43

44 Figure 74: Unrouted service pipe in basement 1 ceiling void to be directed to nearest drainage point and ceiling replaced in this area. Figure 75: Document archive reception area has water supply valve chamber which requires rechecking for leaks, rerusting and repainting of the valve housing and re-plastering of the adjacent wall. 44

45 Figure 76: Main sewer launder pipes within the building run directly through the archive document store. These pipes often get blocked which results in sewer entry into the document store. It is suggested that a new service duct which is appropriately waterproofed is installed to ensure that if the systems leak, the spillage can be contained. Architectural guidance is required in this regard. Figure 77: Sewer leaks are present from overflows caused from occasionally blocked pipes on the floor above are evident. Containment areas for such sewerage issues is required from architectural guidance. 45

46 Figure 78: There are scattered piles of building rubble on the building roof that needs to be removed. Figure 79: There are scattered piles of building rubble on the building roof that needs to be removed. 46

47 Figure 80: Pavement at the southern entrance to the building requires patching of the concrete surface in the sidewalk zone. Figure 81: On the southern pavement a pipe exists which appear to serve no purpose that is a tripping hazard. This pipe to be removed and sidewalk reinstated locally. 47

48 Figure 82: Service covers on the eastern face of the building need to be removed, cleaned and refitted and the pavement repaired locally. Figure 83: The sidewalks are uneven and untidy. It is recommended that the paving on the pavement is uplifted and relayed. 48

49 Figure 84: The eastern face of the building has settled leaving the retaining walls below pavement level open to the elements. Figure 85: Service covers are missing and require replacement on the northern sidewalk. 49

50 Figure 86: The storm water drain system is blocked on the Northern side of the building. As a water pipe is leaking further up the street, there is a large volume of water standing in the street adjacent to the 75 Fox street building. 50