largest residual estate of prefabs, presently consisting of 187 Uni-Seco bungalows, but the demolition of all but six was announced in 2011. Unity Structures (THP) Unity Structures were a construction company based in Rickmansworth. Using common storey-level precast reinforced concrete panels, they produced various updated versions of their bungalow and twin-storey house variations. Using metal bracing within the cavity and metal joists connected at column joints, the PRC columns act as mullions. Copper straps tie the inner panel to outer PRC panel on earlier variants, while later the copper strap fixed to column holding just outer PRC cladding panels. Although the design incorporates significant steelwork resulting in fair current structural condition, the concrete used in casting is decaying, and resultantly leaks chlorides. This results in internal staining through panel joints, and corrosion of the metal reinforcing and straps. A Unity Structures bungalow originally located in Amersham is preserved at the Chiltern Open Air Museum. Wimpey no-fines George Wimpey & Co., being a house builder, focused on both design but also speed and ease of construction. Their method used "no-fines" concrete, the composition of which used no-fine aggregates. Using huge reusable moulds, they were held in place as the concrete for the entire outer structure was poured in one operation. The ground floor was also concrete, while the first floor was made of wooden floorboards. Interior walls were a mixture of conventional brick and blockwork construction. Wimpey's design was particularly successful, resulting in many thousands built, and still occupied today. Other types There are: Hamish prefabs (types 1 and 2) Duplex Sheath prefab Bricket Wood Special prefab Blackburn Orlit prefab and even a pre-fabricated gem known as the Foamed Slag. Residual housing stock today The strength of the post-war temporary prefab housefast construction over an aluminium, steel or wooden frameis today its weakness. The properties were only designed to last 10 years, and so some of the quality standards were not as high as they would have been should a longer life have been envisaged. Secondly, the quality of metal production then was not as good as it was now, but it should be remembered that in only the previous few years British manufacturing plants had become adept at producing a consistently high quality product for the war effort, and so standards were consistent. The quality of a steel-framed prefab house, which can be suffering from rust, or a wooden house