HM The Tower of London

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1 HM The Tower of London Installation of roofing slates to increase projection of coping stones and to reduce damp levels in the walls of the wakefield tower (fig.1) Overview of the Wakefield Tower from the centre of the premises after installation of roofing slates 1

2 London Stone Conservation Ltd 2008 Company: London Stone Conservation Ltd Unit 25, Enterprise Row Rangemoor Road London N15 4LU Tel: Reported by: Hohi Ikeda (Conservator) Date of Report: 29/10/2008 Location: Wakefield Tower ( ); south side of the Tower of London Aims: Investigation of effectiveness of the use of roofing slates as a projection to prevent the outer wall of the tower from direct contact with rain (The roofing slates would be left in the upper north-east side just below the coping stones in the tower for six months at least). Reduction of long-term damage caused by damp to the walls both inside and outside the Wakefield Tower Condition: The Wakefield Tower has suffered from chronic, long-term trapped moisture (damp), possibly caused by the failure of the coping stones at the wallhead. The areas affected by damp are located in the upper north side of the tower. A large darkened area of persistent moisture can be seen in the north outer wall (figs.1, 2). Decay caused by damp, such as de-lamination of limewash, lime plaster and lime mortar, is evident on the surfaces of the walls within. 2

(fig.2) Overview from the north-east side before installation of

There is no remarkable damage at roof level to the fabric of the

3, 4): no apparent failure in the joints or the lead work (fig.

3 (fig.2) Overview from the north-east side before installation of roofing slates Darkened area (damp) Rooftop of The Wakefield Tower There is no remarkable damage at roof level to the fabric of the tower on the whole (figs.3, 4): no apparent failure in the joints or the lead work (fig.5); no sign of trapped moisture in this area. White Tower (fig.3) North-east inner wall (fig.4) North-east inner wall Drain pipe 3

(fig.5) Lower areas of the north-east inner wall North Side Outer

recognisable in the upper region of the wall.

long-term influence of damp, as the area s discolouration is most

Although the presence of relatively recent re-pointing can be seen,

4 (fig.5) Lower areas of the north-east inner wall North Side Outer Wall (from West to East) A large darkened area due to damp is recognisable in the upper region of the wall. It is present from the west to the east side of the tower (figs.6, 7). The arch-shaped area s upper side clearly exhibits the tower s long-term influence of damp, as the area s discolouration is most remarkable (figs.8, 9). Although the presence of relatively recent re-pointing can be seen, there are concerns about joint failure and damage to the stonework. These areas tend to be more weathered as they project. (fig.6) North-west side before installation (fig.7) North-east side before installation 4

Water (rain) directly hit the area (fig.

5 Water (rain) directly hit the area (fig.8) Close up of the area from the ground (fig.9) Close up of the area from the east side Tower Interior De-lamination of limewash and lime mortar can be seen in the upper north-east side wall. It is obvious that the inside wall face of the tower has been affected by long-term damp as the external wall. Damaged areas (fig.10) Tower Interior 5

11) Four different projections were set up by inserting a plywood board (length 1500mm approx) underneath the coping stone (fig.12).

6 Experimental Works: 1. Trials using different projections to investigate the depth necessary to protect the area below from rain 2. Installation of a second trial projection using slates and lime mortar Trials using different projections to investigate the depth necessary to protect the area below from rain (fig.11) Four different projections were set up by inserting a plywood board (length 1500mm approx) underneath the coping stone (fig.12). Each projection from the wall was 110mm, 130mm, 150mm and 200mm respectively. After inserting the board, water was sprinkled (imitative of rain) onto the top of the coping stones in order to ascertain what projection would be needed to protect the wall below from direct water penetration (fig.13, 14). The 200mm projection was the only one that successfully deflected the water from the wallhead below. Its first contact point was the buttress in the lower part of the tower at eye level (fig.15). Therefore, it was decided to employ the 200mm projection. (fig.12) Trials using plywood before watering (fig.11) Watering without projection Water made contact with the wall just below the coping stone. 6

Water made contact with the wall (fig.13) During watering (fig.

15) 200mm projection from top Installation of new projections using

installed just underneath the coping stones using Cumbrian roofing slates

7 Water made contact with the wall (fig.13) During watering (fig.14) During watering Buttress (fig.15) 200mm projection from top Installation of new projections using slates and lime mortar Projections of 200mm depth and 1500mm width were installed just underneath the coping stones using Cumbrian roofing slates wedged into position with lead packers (fig.16). All the joints were pointed with lime mortar to match the existing pointing mix. 7

be left in position for six to twelve months in order to ascertain its effectiveness in

8 Projection (fig.15) After installation of the projection from the top (fig.16) After installation from the east side Results (Conclusion): The slate projection will be left in position for six to twelve months in order to ascertain its effectiveness in drying out the fabric of the wall, both interior and exterior faces. Regular visual inspection shall be required. 8

abqstudio Damp Exercise St John the Evangelist, Penge Sean Albuquerque - Year 1 February 2011 chartered architects and designers

abqstudio Damp Exercise St John the Evangelist, Penge Sean Albuquerque - Year 1 February 2011 chartered architects and designers Damp Exercise St John the Evangelist, Penge Sean Albuquerque - Year 1 February 2011 Contents Introduction 1 Damp Generally 2 The Inspection 4 Conclusions 8 Drawings 9 Interior Photographs 12 Exterior Photographs