Following the tragic Grenfell Tower fire on 14th June. Southwark Council created a dedicated email address for residents in the borough who had fire safety concerns. They also held a public meeting on fire safety at the Old Kent Road Fire Station on Monday 26th June 2017. Southwark Council's Stephanie Cryan (Cabinet Member for Housing) and Gerri Scott (Strategic Director of Housing & Modernisation) attended, and I raised a question at that meeting about compartmentation of my flat potentially being breached by the gaps and cracks in my property. I was assured it would be investigated.
In the meantime, I sent images of the cracks to London Fire Brigade and received this reply from a Technical Advisor, confirming my suspicions.
I immediately forwarded this email to Southwark Council, urging them to move my family out of this property. Southwark agreed to place my family in 'band one' - the highest priority band on their housing waiting list and arranged to send out a team to assess the cracks in my property. I insisted on this occasion, that they must also send an independent building surveyor, not attached to Southwark Council.
On 29th June the team attended, comprising of a Southwark Council Senior Building Surveyor, a Southwark Council Fire Safety Officer and an independent Structural Surveyor from Sinclair Johnston Chartered Surveyors. The independent surveyor, upon opening up the architrave joints in the corners of the rooms in my flat, immediately discovered that the gaps posed a great risk.
Work was carried out immediately to seal the gaps with loft-insulation type material and seal over them with a fire-proof putty. I immediately realised the gravity of the situation and instructed Southwark to look at other flats within the block as I knew some of my neighbours also had cracks. They were reluctant, but eventually agreed and a team began knocking on doors. Subsequently it was discovered that previously reported cracks, across all four towers posed a massive fire risk. The teams worked late into the night to temporarily seal the gaps, and 24-hour fire marshals were brought in to patrol every second landing in the towers. I have since officially requested the fire risk report that was carried out on my flat on 29th June but have not received it.
The report from the independent surveyor at Sinclair Johnston (29th June) is below:
1.1 Concerns have been expressed by the occupants of Flat X regarding movement that they have observed within their flat between the eastern external façade and the internal walls and floors
1.2 Sinclair Johnston & Partners have been appointed by the London Borough of Southwark to view the flat and to advise on the structural engineering implications of this movement.
1.3 We visited Bromyard House on the afternoon of 29th June to view the cracking within Flat X. Our inspection was carried out jointly with Peter Clarke of Southwark Council and with Fire Officer Ajmal Khan. The weather was dry and warm.
1.4 Preliminary comments are made on the basis of a simple visual appraisal. A more detailed consideration will be required following further research and investigation and a number of recommended actions are made in this report, following which structural engineers will be able to comment on the implications of the movement in more detail. This is discussed further below.
1.5 Architrave cover strips were removed from between the Eastern elevation wall and the internal return walls was undertaken at the time of our visit. No other opening up or physical investigations were undertaken. No assurance is given that any areas which are covered up, hidden from view or inaccessible are free from corrosion, rot, decay, cracks or other defects.
1.6 This report is limited to the structural aspects only and excludes windows, services, drainage, cladding, finishes, etc.
2.0 DESCRIPTION OF THE PROPERTY
2.1 Bromyard House is a 14 storey tower block that is believed to have been built circa 1965. It is one of 4 No. similar tower blocks within an area on the northern side of Commercial Road known as the Ledbury Estate.
2.2 The tower blocks are believed to have been designed by the GLC Architects and were constructed, as were many such blocks at the time, using a form of prefabricated precast concrete large panel system. Un-verified documents suggest that Bromyard House was constructed using the Larsen-Nielsen panel system, a system that was used widely in London at the time. The infamous Ronan Point tower block that suffered a partial collapse in 1968 also utilised the Larsen-Nielsen system of precast concrete.
2.3 Flat X is located on the 12th (penultimate) storey and is on the south-eastern corner of the building. The reported movement is experienced along the main glazed length of the flat facing approximately eastwards.
2.4 In the absence of survey plans we have marked up an indicative plan of flat 50 for reference purposes only. This plan is included in appendix A.
3.0 SITE OBSERVATIONS
3.1 The external walls are formed of precast concrete panels with horizontal construction joints at each floor level and with vertical construction joints at corners and at intervals as indicated on the attached key plan. The mastic sealant to the external side of the joints has been replaced recently. The external wall panel thickness could not be accurately measured, but appears to be approximately 200mm thick with an irregular exposed stone aggregate external finish.
3.2 There was no evidence of insulation, or other dry lining to the internal face of the external concrete panels.
3.3 The localised removal of cover strips at the junction between the external eastern wall and the return internal walls exposed the concrete faces and found no plaster lining.
3.4 The floor construction is also of precast concrete construction, but it is currently unclear whether the precast panels have a screed topping. The soffit of the floor above has an exposed painted concrete surface and there is a V- shaped arris line visible in the soffit of the floor slab above Flat X that runs parallel with the glazed elevation that faces eastwards. This arris line indicates the joint between floor panels and suggests the floor panels in this part of the building span parallel with the eastern elevation, with the majority of the floor load being supported by the internal and flank walls that run at 90 degrees to the eastern elevation. No significant cracking was noted along these joints.
3.5 It is believed that most of the main internal walls are also of precast concrete construction. The sound on impact confirms that the wall panels that run perpendicular to the eastern elevation are main loadbearing elements.
3.6 There is a line of horizontal cracking between the eastern external wall and the soffit of the floor slab above. This cracking measured approximately 2mm wide in the bedroom adjoining the Party wall and measured approximately 4mm wide in the adjoining bedroom. The occupier of flat X advised that this cracking was of longstanding and tended to increase in width during hot sunny
weather. We were advised that under recent hot conditions the gap was wide enough to insert fingers in to the open joint and appeared to open up within the course of a couple of days.
3.7 We were able to pull back the carpet and underlay locally to expose a similar crack between the eastern external wall and the floor slab. We were able to insert a 110mm long knife blade freely down this gap towards the flat below and freely up the corresponding gap at the slab soffit joint above. This suggests that there is a clear air gap that exists between upper and lower dwellings and that the outer edge of the floor slabs locally stop before reaching the inside face of the eastern elevation external wall.
3.8 Use of an endoscope down the junction of the floor with the façade wall confirmed the open nature of the joint. There was even a suggestion that the camera image was picking up a glint from the glazing below.
3.9 The occupier of flat X reported that they could clearly hear their neighbours above and below and suspected the open joint was largely to blame. She also reported that prior to the mastic joints being replaced, driving rainwater often poured in through this open horizontal joint. We have also been advised by the occupant of flat Y (Floor below but at the north-east corner of Bromyard House) that they have similar patterns of movement and one of their windows recently fractured. We understand that similar movements have been reported elsewhere.
3.10 We removed the architrave cover strips from the corner of the middle bedroom where they cover the vertical joint between the internal wall and the eastern elevation wall. This exposed an open joint that had been partially stuffed with some form of mineral wool. The joint width between the internal wall and the façade measured 25mm at the top and gradually reduced down to 10mm width at the base. It is probable that the vast majority of this open joint width was original, and it was unclear whether significant differential movement is occurring at this location.
4.0 DISCUSSION AND RECOMMENDATIONS
4.1 The clear air gap between the floor panels and the inside face of the eastern elevation wall is of great concern, particularly given that this has been reported in a number of locations.
4.2 We are not qualified to comment on fire issues. However we understand that the Fire Officer Ajmal Khan has advised that the current open joints would allow the free passage of smoke and possible fire from one dwelling to another and measures should be undertaken as soon as possible to seal these gaps.
4.3 It should be noted that any such sealant measures should be able to accommodate continued differential lateral movement. At this stage we anticipate that a minimum allowance should be made for the reported movement of 10 to 15mm, but further studies are required to confirm whether this is appropriate. We assume that the Fire Officer will propose a suitable detail. We suggest that until a full structural engineering assessment has been completed, these open joints should not be infilled with a rigid material as this would prevent movement recovery and could possibly complicate any structural issues. This can be reviewed once more is known about how the various joints have actually been constructed.
4.4 The concern from a structural engineering point of view is, what are the effects of these cycles of movement on the building structure and in particular has the horizontal tieing action between the external wall panels and the internal floor slabs and internal wall panels been compromised?
4.5 It is plausible that the reported movements are caused by thermal changes acting on the external precast concrete wall panels in comparison to a relatively stable internal environment. Concrete will tend to expand when exposed to increases in temperature. What is surprising is the extent of the reported movements and the pattern of this movement. The effect that the movement has on the ties between the façade and the internal structure needs to be investigated as a matter of urgency.
4.6 Precast concrete panel system buildings remain stable provided adequate ties are present between adjacent panels. A review of all such buildings should have been undertaken post Ronan Point and a search for, and a review of this report should be the starting point for any structural assessment.
5.1 It should be stressed that the comments made above are based on a very brief initial viewing of Flat X. A greater understanding is needed of the pattern of movements both at flat X, elsewhere in Bromyard House and indeed in the other similar tower blocks on Ledbury Estate.
5.2 Very little is currently known about the construction details of the connections between the external wall panels and the floor panels and between the external wall panels and the wall panels that intersect at 90 degrees and this is essential to understand whether the movements are compromising tie details. The following actions are therefore proposed:
5.2.1 Arrangements should be made to visit flat Y, any other flats in Bromyard House where movement is suspected, and in the similar Tower Blocks in Ledbury Estate where similar movements have been reported. Ideally tell tales should be fitted across the cracks and measurements should be taken to establish patterns of movement.
5.2.2 Southwark Council should search their archives and other records for any information in relation to these tower blocks. Ideally the original drawings are needed, but any information, past reports, etc may be of help in confirming the type of large panel system used on the Ledbury Estate. With that information it may be possible to determine theoretical construction details.
5.2.3 Structural engineers should undertake their own research to see if they can find anything of use.
5.2.4 The results of Southwark’s and the engineer’s research will dictate the form and extent of investigation works that will be required. It is currently anticipated that investigation works will be required within void flats and could involve specialist surveying using radar scanning and physical opening-up to confirm the survey results and to establish as-built construction details.
5.2.5 Further investigation and testing may be required depending on the results of the research and initial investigation.
5.3 It should be confirmed whether the 4 No. tower blocks on Ledbury Estate have been assessed in the past by a structural engineer as having reasonable robustness and resistance to disproportionate collapse. It would not be uncommon for some localised strengthening to have been recommended as a result of such a review and it should be confirmed that any recommended strengthening was actually completed.