Dennis-Wild Steel Framed House – Non Traditional Construction
The Dennis-Wild Steel Framed House
- Manufacturer: James Wild & Co (Housing)
- Type: Steel Framed
- Period built: 1920’s
- Number built: 10,000
- Alternative names: Dennis, Dennis-Wild Patent Steel Frame, Composite System, James Wild.
Shortly after the first World War of 1914/18, a number of committees were set up by the British government to examine the construction industry and to report on ways of solving the acute housing shortage and the severe lack of skilled labour and building materials.
The 1919, standardisation and new methods of Construction Committee, invited suggestions from the public for novel methods for building houses.
The committee received a large response to the invitation, resulting in a new list of approved methods for construction being published, which covered the Committee’s work up to the period of April 1920. The Committee finally ceased to function in 1921.
The method of construction used in the Dennis-Wild system is not featured in the original 1920’s list of approved construction methods but due to the fact that over 100 Dennis-Wild houses had been approved for construction in Blackpool during 1922, it is considered highly likely that Committee provided and approved this development.
Interestingly, the Burt Committee of 1942, lists two different sponsors for this building system. The first being, James Wild & Co (Housing) Ltd of Blackpool as the sponsor of the Dennis-Wild system and Edgar B Dennis, also of Blackpool which is listed as sponsor for the Dennis system, which according to the description provided,appears remarkably similar to the Dennis-Wild System.
No date is listed for the Dennis system, and no further mention of Edgar B Dennis can be found. It is possible that these two separate sponsors may have merged to support the one single system that we know today as the Dennis -Wild system.
During the 1920’s approximately 9,000 Dennis-Wild type houses were built on various sites in England with further undocumented numbers also being constructed in Scotland and Wales.
The Dennis-Wild House was typically built as 2-storey semi-detached and terraced houses.
These properties typically have a medium pitch hipped roof that is covered with either tile or slate. The external walls are constructed using standard brick but surface design does vary, often with a split in material usage between the upper and lower elevations. Whilst brick is typically exposed at the lower elevation, the upper elevation may be rendered, pebbledashed or hold hanging tiles including slate above, some may even be brick up to eaves level. Some of these houses also have single storey bay windows at the front elevation. The roof will typically have a Cradle roof truss incorporating iron tie rods.
Externally, the Dennis-Wild house appears to be of traditional construction, typical of the period.
There is no indication that the structure conceals a steel frame.
Two storey dwellings range from semi-detached blocks to terraces of up to six dwellings. Terraces have ginnel access to rear gardens.
Roofs generally have hipped ends. Some semi-detached blocks are rectangular in shape, others have bay windows to the ground floor and some have projecting extensions to the flank end.
Terraces are either rectangular in shape or the end dwellings is rotated 90 degrees to the main structure whilst the front elevation projects beyond the building line.
External finishes are varied. The majority have facing brickwork to first floor level, often finished with a projecting band course. From the first floor to the eaves the walls are either tile, slate hung or rendered with pebble-dash. Alternatively, walls may be of facing brickwork from ground to eaves level sometimes with decorative quoins to the facing brickwork.
Internally, the ground floor rolled steel stanchions to the middle of the front and rear elevations may protrude from the line of the wall, and in such cases the stanchions are likely encased in concrete or plaster. The stanchions of the separating wall and the flank end wall are not always visible.
The main floor support spans horizontally between the middle stanchions in the front and rear elevations. Ceiling supports are often below the ceiling line and are often encased in timber. The floor support channels are not always visible.
Where the second storey is rendered or fitted with hung tiles, walls to the storey may be of thinner construction.
The only accurate indication of a Dennis-Wild house is the presence of the patented Cradle Roof Truss, which is unique to this system.
The typical frame components for one house in a semi-detached pair are:-
Seven Eaves height “I” section rolled steel stanchions.
One Single storey height “I” section rolled steel stanchion.
One “I” section rolled steel first floor support beam.
Two Channel section rolled steel first floor support beams.
Three Angle section rolled steel ties at first floor level.
A typical frame has three eaves height stanchions in both the front and rear elevations, one located at each flank end corner, another at about mid-point along both walls, and one on the line of the separating wall, which is shared between adjacent properties.
A further eaves height stanchion is located at about mid-point along the flank end wall.
At first floor level the stanchions are connected by two floor support channels, a main floor support beam and two angle ties. The floor support channels connect the stanchions along the flank end wall and other stanchions along the line of the separating wall.
The main floor support beam spans between the mid-point stanchions in the front and rear elevations.
Angle ties connect the stanchions in the front and rear elevations.
A timber beam typically 5 ins x 3 ins is connected to the stanchions around the perimeter at first floor level and acts as a sole plate for the studwork in the upper storey.
A similar timber beam spanning over the tops of the stanchions, provides the only connection between the stanchions at the eaves and also acts as a head plate for the studwork and a wallplate for the roof construction.
Vertical timber studs are fixed between the two beams at regular intervals.
External walls are of cavity construction to the first floor level.
The outer leaf is generally of 4 ins brickwork, finishing with a projecting band course, and the inner leaf is of 3 ins blockwork. First floor to the eaves the wall is tile or slate hung on battens fixed to timber studwork. The inner leaf is of 2 ins blockwork built off the first floor boarding and nailed to the inner face of the timber studwork.
The internal finishing is of sand/lime/cement backing coat and a plaster finishing coat.
Separating Wall: The separating wall is usually of cavity construction with two leaves of 3 ins blockwork with a 2 ins cavity between.
Partitions: On the ground floor the partitions are typically of 4 ins brickwork and 2 ins blockwork. On the first floor the partitions are of 2 ins blockwork throughout
The ground floor to the living area of the house is of suspended timber construction, with 4 ins x 2 ins joists at about 15 ins centres spanning from the front elevation towards the rear elevation and supported on honeycomb dwarf walls. The floor to the kitchen area is of solid concrete.
The first floor is commonly of 6 ins x 2 ins timber joists at about 16 ins centres and span from the flank end wall to the separating wall. They are supported on the steel channels at the flank end and separating walls and on the main floor support beam at about mid-span.
The ceilings are usually of lath and plaster throughout.
The hipped roof is largely conventional in construction, except for the single James Wild Patent Cradle Roof Truss. The unique feature of this truss is the use of steel rods to support the strut below the purlins, avoiding the need for a load bearing wall below.
The rest of the roof is constructed with hip and common rafters in a conventional manner using the timber eaves perimeter beam as a wallplate.
Variations: There are a wide variety of constructional variations found with this property type that are not listed here.
- Render pebble-dash external finish to the upper storey on either:-
- 3 ins blockwork nailed directly back to the timber studs or secured with butterfly wall ties nailed to studwork:
- Or on 3 ins blockwork or brickwork on edge cavity construction.
- Absence of the timber perimeter beam at first floor level.
- Absence of timber studwork to upper storey.
Facing brickwork outer leaf from ground to eaves level, sometimes with decorative quoins.
- Surface corrosion of the steel frame has been frequently observed, particularly at corner stanchions.
- Severe corrosion with loss of section limited to lower portion of stanchions and at lateral connections at first floor level.
- Excess moisture or water ingress can cause severe corrosion to all stanchion bases.
- In the majority of cases, any protective coating if applied, is often found to be absent or significantly breached.
Deterioration of Timber Components:
- Severe decay to perimeter beam at first floor.
- General decay has been observed during instances of demolition.
- Long and unequal spans in the roof purlins can lead to bowing.
Deterioration of the External Components:
- Vertical cracks in brickwork up to first floor coinciding with stanchion locations.
- Bulging of the brick walls on both the rear elevation and flank ends.
- Vertical cracks often visible to the pebble-dashed render.
- Spalling of the pebble-dashed rendering from brickwork substrate.
- Tile and slate hanging to walls of the upper storey can deteriorate.
- Insufficient wall ties found.
- Deterioration of brickwork surfaces below DPe level.
GUIDANCE TO INSPECTION
This section is a compendium of deterioration and faults that have been reported to or identified by BRE which are specific to the Dennis-Wild steel framed house, much of which has been mentioned above
The principal defects are:-
- Corrosion of the stanchions at the bottom.
- Corrosion of the stanchions at first floor level and up to eaves level.
- Rot in the timber perimeter beam at first floor level.
- Bowing of the roof purlins and tilting of the roof wall plates.
- Cracks in the brickwork at stanchion locations.
- Bulging of the external walls.
- Spalling and cracks in the pebble-dashed rendering to the upper storey.
- Deterioration of and damage to the tiles or slates used in the vertical tile hanging.
- Insufficient numbers of wall ties.
- Ties not effectively bridging the width of the cavity.
- Ties sloping inward.
- Corrosion of ties particularly where bedded in black-ash mortar.
- Frost damage brickwork surfaces.
- Moderate to severe corrosion of RSJ stanchions has been noted particularly at stanchion bases.
- Damp proof course is not always present.
- Vertical cracking of brickwork can sometimes be found where stanchions are located.
- Vertical cracking has been noted in the upper floor render, particularly at the timber stud locations.
- Bulging of external walls may be present.
- Wall ties: Can be insufficient, failure to bridge wide cavity, may also suffer from corrosion.
- Decay of timber perimeter beams at first floor level has been found.
- Bowing of timber purlins and tilting of timber wall plates has been noted.
- This system was also used to produce flats.
- Surface corrosion of the steel frame.
- Severe corrosion with loss of section to the lower portion of stanchions.
- Corrosion to lateral connections at first floor level.
- Severe corrosion to corner stanchions, through water ingress in exposed conditions,
These do not constitute a comprehensive list of possible defects. Equally not all the above defects will necessarily be present in one property.
Nonetheless this list serves to highlight features which should be subjected to close examination as part of any overall inspection procedure for Dennis-Wild houses. It is emphasised that if significant corrosion of the steelwork has occurred, the extent of deterioration may be masked by the corrosion product itself. In such cases it is difficult, if not impossible, to determine the condition of the steelwork solely by visual means. This limits the effective application of purely visual inspection techniques, including the use of optical probes such as borescopes. If corrosion is seen to exist, the component should be exposed in order to enable the extent of deterioration to be determined by removal of the corrosion product.
GENERAL COMMENT ON CONDITION
The observations in this report result from examination of Dennis-Wild houses in England, Scotland and Wales. Some of the houses were in their original condition, others had been or were in the process of being refurbished. As with all steel framed houses, repairs to the frame are straightforward in principle. Affected members can be cut out and replaced by new steelwork adequately protected against corrosion.
This article has employed the use of publicly available published data including: Data provided by The National Building Studies Special Report No 16. “The corrosion of steel in steel houses”. HMSO 1951 & The publication, Post War Building Studies No 1. “House Construction” – First report of the Burt Committee. HMSO 1944.
Data published by The Building Research Establishment has also been consulted. A Full copy of the BRE publication titled, Dennis-Wilde Steel Framed Houses can be purchased from the BRE bookshop website.
Other extracts include work published by E Grant, based on site studies and other work carried out by J R Britten, R N Cox, A Christie, P Finch, E Grant, K C Harling, H W Harrison and J Thompson.