- Manufactured by: Henry Boot & Sons
- Type: Metal framed
- Number Built: England 7200 / Scotland 1000
- Period of Manufacture: 1910 – 1930
- DESIGNATED DEFECTIVE ENGLAND & WALES
The structure of the early 1900s Boot house comprises of twin, precast reinforced concrete columns set at approximately 3 ft centres.
Each column is constructed with an inner and outer section located within the two leaves of the external walls. They were joined together at the ground, first floor and roof levels.
Within each storey the twin columns were tied together using mild steel wall ties. A precast reinforced concrete ring beam component were keyed into these columns at first-floor level in the inner and outer leaves.
At the eaves level a concrete ring beam was cast in situ (on site and in place) against a timber wall plate, which stabilises and locates the columns and other wall components.
The two leaves are formed by breeze block, which are also keyed into the components of the columns.
Where an opening is present, the twin columns were joined across the cavity to form the reveals.
External walls: Generally rendered throughout.
Floors and roofs: Traditional construction.
- The general condition of Boot Houses very much depends on the type of aggregate that was used in the concrete components. Those containing dense aggregate tend to be in better condition than those containing breeze based aggregates which are likely to crack to some extent.
- There may be a potential risk to safety in extreme circumstances in houses where columns have deteriorated substantially, although it is unlikely that such a risk could develop without cracking becoming evident on the external walls of the house.
Need For Action: There is generally no need for urgent action, however early remedial action should be considered once cracking of structural concrete components has been observed.
General Stability: There are four factors which contribute to the overall stability of the Boot house. These are:
- The interaction of blockwork with the columns to form external shear walls.
- The mild steel tie rods within the cavities which tie the corner columns to adjacent columns.
- The ring beams at first-floor and eaves level, which help to locate the columns and redistribute local loads.
- Internal blockwork partitions and floor construction.
Evidence from BRE inspections and reports from one local authority did not identify any Boot houses in danger of overall collapse. Considerable structural weakening had been identified in a number of components at two sites, but the combination of circumstances required to bring about overall instability had not yet occurred.
You can find a far more in depth report as the overall condition of Boot Houses, Titled, The structural condition of Boot pier and panel cavity houses, published by the Building Research Station and available through the BRE Press website.
One of the main reasons for this may be the visible external signs of distress which have caused authorities to investigate their houses before deterioration had progressed to a point where it became critical.
In the early 1980’s around 1500 Boot properties on the Saffron Lane & Braunstone Estates in Leicester were to contain a wide number of serious structural defects pertaining to degradation of both the steel frame & concrete that was used in these constructions. Demolition of around 1000 Boot properties on the Saffron Lane Estate began in 1985 to make way for new, replacement housing.