Identification Wapping Mystery - Help Please!
Hello - we've been going in circles for weeks trying to purchase a property in Wapping (47 Garnet Street, Wapping, E1W 3QS).
The house is of concrete construction and was built in c.1980. Both our surveyor and Natwest's valuation survey flagged that it may be PRC and defective, but the verbal commentary from both was that it was unlikely to be one of the defective types. The sellers paid for a more detailed non-intrusive survey which said it does not appear to be one of the defective types. However, the lenders are not satisfied as nobody can find any definitive record of how the house is built.
I've pasted the more detailed survey below... I'm happy to email it to someone along with any pictures we have if helpful. If anyone can help us figure out what sort of risk we may be taking on here, that would be much appreciated.
The property in question is a semi-detached private dwelling on three storeys in a terrace dating from c.1980.
The original house is of non-traditional construction, having a cast in-situ concrete frame instead of loadbearing walls of brick and block masonry.
However, it is not one of the recognised types of pre-cast reinforced concrete (PRC) house and not one of the types identified as defective under the 1985 Housing Act.
The method of construction is somewhat unusual for low-rise domestic housing, but of course is widely recognised a conventional for larger office and residential buildings, with no inherent defects when modern techniques of quality control are employed.
The appearance of the houses is conventional, with the concrete components entirely concealed and thus inaccessible for inspection.
The only indication of the concrete framing was on the outside corners of the street elevations, where the occasional hairline cracks are the result of curing shrinkage and not indicative of deterioration of the concrete or structural movement.
There was no visible sign of structural movement, cracking, spalling or corroding reinforcement visible anywhere on the terrace, and the exterior of the buildings were protected from the elements by painted stucco or on the rear elevations, hung tiles.
Many of the properties had their lofts converted into attic bedrooms, and the subject property was converted with Building Regulations approval in 2010.
The property was extensively refurbished in 2015 and the photographs on the following page were provided by the owner and show some of the concealed structure.
These show a pair of concrete beams at first floor level running rearwards toward the back wall of the house.
They are supported on a pair of steel box-section posts where the internal wall had been removed during remodelling of the ground floor space.
The beams are integral with the reinforced concrete first floor slab, forming a down-stand edge beam to support the floor.
Other internal walls are non-loadbearing partitions of timber studwork.
The ground floor was concealed but assumed to be a ground-supported concrete slab. There was no cellar or basement storey.
The steel cleat visible at the end of the floor beams does not provide vertical support but provides lateral restraint by tying in the rear wall to the first floor.
The front and rear walls of the terrace are alternately set back on the terrace, while the upper storeys are aligned at the rear, the tile-clad walls being supported at first floor level.
Although the foundations were not inspected, these could be either a concrete strip foundation or a reinforced raft slab, or a piled foundation.
From published geological maps, the subsoil in the locality is identified as London Clay overlain by Alluvial deposits of Clay, Silt, Sand and Peat.
This material is inconsistent and is bearing capacity is affected both by the highly compressible organic matter as well as the geologically recent sediments which have not been thoroughly compacted by the passage of aeons.
Borehole logs dating from 1988 nearby on the corner of Garnet Street and Wapping Wall reveal a considerable depth of Made Ground (silt and brick rubble from earlier activities) before a dense stratum of Gravel is found at 6.4 metres’ depth, beneath various layers of organic silty Clay.
Consequently, a piled foundation would be the expected choice for most buildings on the site, although a raft foundation could potentially be viable on a reasonable well-compacted layer of filled ground.
Fortunately there were no signs of foundation movement or disturbance in the terrace, and the risk of subsidence is therefore held to be low.
The roof structure was originally a series of factory-made timber trussed rafters, connected at the nodes with toothed steel plates. These were supported only on the outside walls and would not rely on the internal walls for support.
The conversion of the loft into attic rooms has required the roof to be supported on a platform comprising timber joists suspended from 203x203 UC steel beams spanning between the party walls, with bolted splice connections to ease erection on site.
The apex of the roof would need to be supported on a ridge beam, although this would be concealed above the ceiling of the flat-roofed dormer.
The property is in a sound and stable condition, with no significant evidence of structural weakness or instability, or recent or active foundation movement.
Although the property is not of traditional brick and block masonry construction, it is not one of the defective types listed under the 1985 Housing Act, and is not one of the Large Panel System PRC types identified as being of non-traditional construction.
Consequently, there is no reason why the property should not be considered equivalent to a conventionally-built dwelling and requires no special or unusual treatment or maintenance.
The defects described above would not make the property unsafe or uninhabitable and it should be possible to obtain insurance cover for the building on normal terms.