Designated defective in England & Wales
The Newland house otherwise known as the Tarran-Newland or Tarran-Clyde in Scotland, was constructed by Tarran Industries Ltd, between 1944 and 1956. The structural form of the Newland house is somewhat similar to the Dorran, Myton and Tarran House constructions which were also built by Tarran Industries.
All constructions were based on the use of 16 inches-wide, storey-height precast reinforced concrete panels with the possibility of a number of variations.
Newland Houses were built as 2-storey semi-detached terraced houses. Having a shallow pitch gable roof covered with tiles or profiled asbestos cement sheets. External walls are of narrow storey height PRC panels. The Gable wall apex is of asbestos cement sheets. A flat canopy was fitted over the recessed front door.
Brief Construction outline.
Substructure: Concrete strip footings.
Brick under building and DPC.
External walls: PRC kerb units (1-See image below right), storey height 16" x 11/4" PRC cladding panels [2] bolted together through MS dowels [3], steel cleats [4], timber stud framing infilled with glass wool insulation and lined with plaster board [5]. Panel joints caulked with tarred rope. RSC ring beams [6] on timber bearing plate [7]. PRC cover panels [8]. Timber wall plates [9]. Storey height PRC corner columns [10]. Gable wall apex clad with asbestos cement sheets.
Separating wall: PRC panel cavity wall faced with timber studs lined with plasterboard.
Partitions: Timber stud lined with plasterboard.
Ground floor: Concrete.
First floor: Timber boarding on twin back-to-back RSC floor beams [11] supported on single storey tubular steel columns located at centre of house. Ceilings: Plasterboard. Roof: RSC trusses and tiles.
The Newland system of construction comprises of precast reinforced concrete storey-height tray-shaped panels which are joined at the corners and party wall by precast reinforced concrete columns. Steel channel floor units are bolted together to form a continuous steel ring beam around the structure.
The panels and corner columns are clamped together as shown in the image below, are located at ground level on precast reinforced concrete kerb units.
At first-floor level the steel-channel ring beam is fixed to the upper and lower storey wall panels with hook bolts. Timber bearing plates are sandwiched between the ring beam and the wall panels.
The vertical joints between the wall components are caulked internally and mortar pointed externally.
At eaves level, a timber wall plate is bolted to the panels.
The roof is of a steel truss design and constructed from steel angles. It is fixed down to the timber wall plate and is clad with profiled asbestos cement tiles.
At first floor level, the prefabricated steel-channel floor units span from the front and rear walls to the centre of the house, where they are supported on tubular steel columns. Where the steel channels of the floor units abut other units, ie at the centre of the house, over the support wall and at junctions between adjacent units, the back-to-back channels are bolted together to form an 'I' section.
The floor therefore comprises of a complete steel grillage with the periphery channels forming the ring beam for the external walls.
Overall stability
The construction of a pair of Newland semi-detached houses is unusual in as much as two separate concrete box structures are formed by clamping together adjacent panels which are then additionally connected by the steel ring beam at first-floor level and a wall plate at roof level.
The stability of each house therefore relies upon the wall units remaining connected and forming a box which will carry the vertical loading and withstand the horizontal forces.
The steel grillage provided at first-floor level, provides an effective diaphragm which should eliminate the possibility of local lateral failure of the walls,and will distribute vertical loads onto adjacent wall panels should individual panels become weakened by corrosion of the reinforcement.
Corner columns
The storey-height columns are reinforced with stirrups and four 1/4 in.(6 mm) diameter steel rods. Holes are cast in the columns to take the fixing dowels from the panels. The columns share the vertical loading with the panels, but their prime function is to tie the corner wall panels together providing continuity to the external wall. If deterioration of the post occurs, such that the continuity of the concrete box is lost, the steel ring beam at first-floor level and the wall plate at eaves level should prevent immediate further damage.
Reinforced Panels
The reinforced panels are of a thin section and corrosion of the steel whivh results in spalling and disruption of the panel, will reduce its load-bearing capacity. Disruption of the concrete between the clamping members of the fixing as shown above, could put the fixing under strain or if concrete fails the fixity could be lost.
Kerbs
The precast reinforced concrete kerbs provide support and location for the wall units. Disruption due to corrosion of the reinforcing steel could result in lifting or dropping of panels putting increased load on the fixings and causing distortion of the ring beam.
Variations
At one site inspection, a pair of suspected semi-detached Newland houses was found to be devoid of columns at the corner locations and at the party wall.
Due to the houses being occupied, it was not possible to determine the corner detail, although the joint was clearly mitred
The Newland house is similar in concept to the Myton house but has construc- tional differences in the floor and roof components.
These are:
1 The first-floor joists and roof trusses were specified as steel components, not timber.
2 The ring beam at first-floor level is a steel channel section and not of precast concrete units.
3 The Myton house uses narrow storey height precast reinforced concrete panels for its main loadbearing components. The floor and roof are of traditional timber construction.
