The iron slip cover roofs of Deptford and Woolwich Royal Dockyards 1844-1855
Duncan Hawkins and Caroline Butler with Andrew Skelton
The period 1844 to 1857 saw the erection of eighteen revolutionary widespan iron buildings in the Royal Dockyards of Chatham, Deptford, Pembroke, Portsmouth and Woolwich. 1 Constructed of cast and wrought iron frames and roofs and clad with corrugated galvanised iron (CGI), the buildings served as roofs to Dockyard slipways. The design brief was set by officers of the Royal Engineers, but all detailed design, fabrication and construction was by three of the leading contractors of their day, Fox Henderson, George Baker and Son and Grissells.
Three of these slip cover roofs were built at Deptford Dockyard (Slips 1, 2 and 3) and three at Woolwich Dockyard (Slips 4, 5 and 6). Of the surviving buildings, two are located at Chatham, having been originally built as slip cover roofs at Woolwich then dismantled and re-erected at Chatham as Machine Shop No. 8 and the Boilershop after 1869. The remaining (much altered) building is the Olympia Warehouse (formerly Slips 2 and 3), Convoys Wharf, Deptford, on the site of the former Deptford Dockyard.
The wooden slip cover roofs: 1814-1841
Wooden warships could remain under construction for many years, leading to significant problems with rot prior to launch. 2 By 1812 the Admiralty was considering roofing slipways and docks to alleviate this. The first slip cover roofs in Britain may have been built in 1812/13. 3 However, the first documented covered slips were at Deptford, Portsmouth, Plymouth, and Woolwich by 1814. 4, 5, 6 From 1814 to 1841 the slip cover roofs were framed in timber. They were clad initially with boarding and tarred canvas or paper, with slate from c.1817 but with copper or zinc by 1819. 7, 8 The last wooden slip cover roof constructed was over Slip No. 3 at Pembroke in 1841 which cost £7,500. 9
An evocative 1847 description of the 1841 wooden slip cover roof at Pembroke No. 3 Slip survives:
It is erected over No. 3 slip (calculated for a first rate) in Pembroke Dockyard; its span is 100 feet, and extreme width from eave to eave 160 feet; the entire area of ground covered is 291' 3" x 160' 0". It has twenty four standards 11' 9" apart from centre to centre, in each of the two parallel rows, and eight at the hipped end; and the height from the ground line at the two fore standards to the apex is 60' 7". 10
Examination of the design of wooden slip cover roofs indicates that these were not limited in span or scale compared with their iron successors. 11, 12, 13 The scale and sophistication of these buildings is shown in contemporary images (Fig. 1).
The imperatives to discard timber construction in favour of iron
The replacement of timber with iron in slip cover roofs may in part have been due to durability and maintenance. The cumulative cost of construction and subsequent maintenance of wooden roofs was significant. At Chatham in 1816 the estimated cost for building a wooden 'roof' over the 'first dock and second slip' was £11,650 but the 'second slip' appears again in the estimates for 1818, when roofing it cost £3,000. This appears to have excluded the copper sheathing, for which a comparable sum of £2,635 is available in the estimates for the 'first slip'. 14 Overall therefore the cost of providing the wooden cover roofs over the 'first dock and second slip' at Chatham was perhaps c. £17,285. By comparison the earliest iron slip cover roofs over slips Nos. 8 and 9 at Pembroke Dockyard cost £15,480. 15
Additionally the lighter iron slip cover roofs required significantly fewer supporting columns (standards) than their wooden predecessors, allowing more efficient use of the covered space within the building.
Many of the wooden slip cover roofs suffered significantly from rot. In 1844 it was reported that the wooden roofs over slip Nos. 8 and 9 at Pembroke were totally decayed. 16
The principal imperative for replacing timber with iron, however, was to eliminate the risk of fire. In 1845 (published 1847), Williams observed:
Hitherto the slip roofs have all been made of timber, with coverings of sheet iron, sheet copper, zinc, slates, tarred paper, or canvas. Creditable achievements in carpentry, but presenting masses of inflammable material which prudence suggest the expediency of replacing, as opportunity offers, by constructions free from so fatal an objection. 17
An illuminating text describes working conditions under a wooden slip cover roof at Devonport Dockyard recording that the men working on the future HMS Albion:
are suffering much from the heat of the weather, and the additional heat created by the unavoidable use of candles in the lower part of the slip, which together render their situation very oppressive and scarcely supportable. 18
The potential fire risk of this practice is scarcely calculable.
The first iron slip cover roofs: 1844-1845
Fireproof slip cover roofs were first proposed by Sir Samuel Bentham in 1812 for modifications at Sheerness Dockyard, though Bentham's proposals envisaged masonry walls and cast iron roofs and were never implemented. 19 In 1837 Captain Henry Brandreth, Royal Engineers (1794-1848) was appointed Director of Admiralty Works and the topic was reviewed again. His obituary records:
One of the most important considerations which engaged the attention of Captain Brandreth, as Director of Works, was the gradual substitution of combustible for incombustible materials, having found in the dockyards many temporary wooden and canvas buildings for which he was desirous of gradually substituting those constructed of iron, zinc, slates and tiles; and that sheets of corrugated iron should be supplied to the yards for temporary buildings when required. 20
As Director of Admiralty Works from 1837 to 1846, Brandreth was an advocate of iron construction. 21 In 1837 Brandreth formed a team of (then) Junior RE Officers who were made Supervisory Officers for the Admiralty Works in the Royal Dockyards (Table 1).
The experience of these officers with iron as a building medium appears variable. 22, 23 An indication of this is an 1843 paper by one of their number, William Denison:
The reduction in the price of iron within the last few years has led in many ways to an extension in its application to the purposes of construction; most especially is this to be remarked in the roofs which are so frequently erected over workshops, railway stations, and other similar buildings; where we find light wrought iron taking the place of either wood or cast iron, and considered as superior to both as regards lightness, and to the former, in addition, as regards durability. I have thought it desirable, therefore, to lay before my brother officers specimens of roofs which have been erected with a short description attached to them, sufficient to explain the principles of their construction and I have to thank William Crawshay Esq, of Caversham Park and Messrs Fox and Henderson of Birmingham, who have been kind enough to furnish me with the drawings from which most of the plates are engraved. 24
This shows both that the Royal Engineers were unfamiliar with this type of iron roof construction, and that Denison was reliant on civilian roof fabricators and contractors for technical details.
How early Brandreth was pursuing the aim of creating iron slip cover roofs is unclear, but a surviving document of 1840 in relation to Pembroke Dockyard refers to 'Fireproof roofs for slips. Mr William Potter proposes a plan, to send plan and estimate'. 25 Potter was perhaps a civilian contractor or a civilian member of the Admiralty Works Department. An intriguing possibility is that the concept of the all iron slip cover roofs, as eventually implemented, may actually have its origins in these proposals, put forward by a civilian.
In May 1842 the Admiralty directed that all new slip cover roofs were to be constructed of iron. 26
Brandreth was directed to find out the Master Shipwrights' opinions on their proposed standardised dimensions; the distance from centre to centre across the slip being 82ft 6in, and the distance from centre to centre of standards along the sides of the slip being 13ft 4in. He was also required to enquire, in view of the fact that the slips were placed 70 to 80 ft apart, whether it would be practicable to cover this intermediate space with a double roof supported by a row of columns along the centre. 27
Brandreth drew up a dimensional sketch drawing to show how his standardised slip cover roof might work (Fig. 2), and for the Shipwrights to comment on. The advantages of standardising the dimensions to facilitate design, manufacture (particularly prefabrication), and budgeting projects can be readily understood.
Most of the Shipwrights agreed with Brandreth's proposals. However, there was significant dissention from the Shipwrights at Pembroke Dockyard:
We beg to observe that there are great objections to the distance of the standards across the slips being only 82ft 6in, they should be not less than 100 feet, but if 105 feet could be obtained it would be much more convenient. 28
Brandreth also noted that the Pembroke Shipwrights objected to the distance intervals of the standards along the slips proposed at 13' 4", preferring a distance of 'about 11 feet' 29 noting also that:
They also consider the row of columns to support the double roofs objectionable, and refer to their letter of the 4th inst. and the accompanying drawing showing how a single roof might be arranged so as not to interfere in the least with the working operations and storage of materials. 30
That the Pembroke Shipwrights submitted an alternative sketch proposal to Brandreth's is noteworthy. Consequently Brandreth proposed:
As it is necessary to settle immediately these dimensions at Pembroke, that the officer of Engineers may construct the pits for the standards — I beg to submit the following observation on the report of the Pembroke Officers. The spaces between the piles in this yard are considerable, and the officers have adopted roofs of very large dimensions, which are in themselves very admirable, affording, in addition to working space storage for assorted(?) materials, and shelter from the peculiarly humid atmosphere of the place. An exception may therefore be made in (illegible) of Pembroke Yard — and roofs of larger dimensions than what I have proposed may be made a subject of consideration.
But as I now am willing to put up an iron roof of a greater span than is absolutely necessary, or particularly(?) desirable, I should be glad, if the dimensions I have proposed, could be approximated as nearly as possible.
I should also like the double roof and row of columns (the latter to be 20 feet apart, or more if wished) to be adopted as light and inexpensive(?) roofs might be applied with great advantage between existing slips, where the span exceeds 70 feet. The master shipwright at Pembroke, suggested an intermediate roof of iron to (illegible) the (illegible) which I think a very judicious plan.
The officers object to the centre row of columns for the intermediate covering as interfering with the working operations, and storage of materials.
I do not think it will interfere with the working operations, because each slip will have its own proportion(?) of space on each side of the columns, and in reference to the storage of materials under these sheds or under the roof of the slip I think this practice, although (illegible) convenient, should as much as possible be avoided, as in the case of the shed, the space should be left as free as possible so that in the event of fire the Engines may be worked to the greatest advantage; and because in both cases of roof and shed, the materials so stowed, would encumber the operations of the fire engine — would from their combustible nature, contribute to the spread of the flames — and could not be easily moved in the case of danger.
I beg therefore finally to recommend that the report may be sent to the Superintendent of Pembroke Yard and that he may be requested to call on the officers, to reconsider their report of the 26th Inst and forward the result with as little delay as possible.
Let this report be put to the Superintendent of Pembroke Yard (as suggested) who will call in the officers to reconsider their report of the 26th of May. 31
After further correspondence the Pembroke Shipwrights won most of their arguments. Brandreth's concession to the Shipwrights, compromising the opportunity to create a standard class of buildings to a pre-designed format suitable for pre-fabrication must surely be seen in the context of his documented ill health, which affected him from 1841 and forced his retirement in 1846. 32
The first timber slip roofs selected for replacement were those over the adjoining slips Nos. 8 and 9 at Pembroke Dockyard, the timber structures being totally decayed.
Williams records that:
Several designs were proposed; but that of Messrs Fox, Henderson & Co, of the London iron works, Birmingham having met with approval, they entered into a contract to put up the two roofs for the sum of £15,480, taking the responsibility of stability upon themselves; they were commenced in September 1844 under the immediate superintendence of their Resident Engineer, Mr J Hughes. 33
The fact that supervision of the buildings' construction was left to Fox Henderson's own consultant John D'Urban Hughes (1807-1874), an experienced railway and bridge engineer, is significant, showing there was no direct supervisory role for the Royal Engineers. As such, it reflected the Royal Engineers' lack of experience with iron roofs as indicated in William Denison's 1843 paper, with the Royal Engineers only responsible for directional control.
Williams, the Supervisory Royal Engineer Officer at Pembroke Dockyard at the time of the roofs' construction, 34 provides a complete description of the new Pembroke slip cover roofs and their erection concluding that the design and construction:
… reflect the highest credit on the well known talents of Messrs Fox, Henderson and Co, which have been most ably seconded by the science and ready resource of Mr J Hughes, who successfully overcame the many difficulties inseparable from the carrying out of so novel and extensive an undertaking. 35
Evans' statement that 'The two slip roofs … are the only ones to which a designer, rather than a contractor, can be definitely attributed' 36 must therefore be judged in terms of the Royal Engineers' own contemporary statement on who had principally contributed to the new buildings.
Fox Henderson's new iron roofs to Slips Nos. 8 and 9 at Pembroke Dockyard, together with a further new iron roof to Slip No. 7 at Pembroke of c.1845 owed much in form and design to Seppings' earlier wooden roofs. 37, 38 In essence it was the fabric of the material components that had changed rather than the principles of roof construction, with iron components being substituted for the wooden components of the earlier buildings.
Tucker observed: 'in form they resembled Robert Seppings' timber ship sheds, but using wrought iron arched principals comprised, in effect, of overlapping polonceau trusses, between cast iron pillars'. 39
Woolwich Slip Cover Roof No. 6: c.1845
Fox Henderson appear to have carried out a similar 'design and build' role at Woolwich Dockyard in 1844-45 where they were commissioned to produce an iron roof to Slip No. 6. The most up to date review of that dockyard's architecture states that this building was 'Designed and fabricated by Fox, Henderson and Co'. 40
This structure was again close in form to Seppings' timber precursors and very similar to the Pembroke Slip Roofs Nos. 7, 8 and 9, 41, 42 using almost identical components, very slightly reduced in scale from those used at Pembroke (Figs. 3 to 6).
The assertion that Roger Stewart Beatson, the supervisory officer of the Royal Engineers at Woolwich from 1845 had designed the cover roof of Slip No. 6 43 appears incorrect, though his predecessor William Thomas Denison may well have specified the dimensions. This building still survives today in skeletal form as Machine Shop No. 8 Chatham Dockyard.
By the close of 1845, Fox Henderson had erected four iron slip roofs (Pembroke Nos. 7, 8 and 9 and Woolwich No. 6), the design and fabrication of which it can be surmised had been carried out by them 'in house' (perhaps with the assistance of external civilian consulting engineers), as 'design and build' contracts based on the latest wooden slip covers designed by Sir Robert Seppings. The erection of the first two roofs at Pembroke had certainly been supervised by Fox Henderson's consulting engineer, John D'Urban Hughes.
In all cases the new iron slip cover buildings combined cast and wrought iron components. The types of component that were made from cast and wrought iron were determined by the methods of manufacture and shaping as well as the physical properties of the material. Typically cast iron is represented as massive columns, frames and beams and wrought iron as built up composites of relatively small components.
Where the iron slip cover buildings of the Royal Dockyards radically departed from contemporary factory, warehouse and railway construction practice was in the adoption of corrugated galvanised iron (CGI) as both a wall cladding and roofing material. CGI had been patented on 30 June 1829 by Henry Robinson Palmer, architect and engineer to the London Dock Company 44, 45 and by 1833 had been used in roofs for the London Dock Company warehouses. 46
Competitive contractors: Baker and Sons
The next iron roofs commissioned were built at Deptford Dockyard over Slip No. 1 and Slips 2 and 3 in 1844-5 47and at Portsmouth Dockyard over Slips Nos. 3 and 4 from September 1845. 48 These were by George Baker and Son of Lambeth. In September 1845 Denison at Portsmouth sent 'drawings of the explanation of this roof and proposed method of closing in the gables and states that Mr Baker's estimates are fair'. 49
A Goad insurance plan from 1889 shows the area of Baker's works as a small, elongated yard with two central buildings, both stores (but one containing a furnace), surrounded by ranges around all four sides. These ranges included a small smithery with two forges and an extensive range of carpenters' shops (Fig. 7).
Although there are no records directly relating to the occupation of the site by the Bakers, the compact nature and suburban setting of the site make it highly unlikely that the Bakers actually made any of the cast or wrought-iron components they used in the Admiralty contracts on these premises. Clearly they sub-contracted this part of their work out. Unfortunately it is now unknown with whom most of these sub contracts were placed, though it is known that Morewood and Rogers supplied CGI and galvanized angle iron for the iron slip cover roof to No. 5 slip at Portsmouth 50, 51 and the ironwork for the Natural History Museum was sourced from Belgium. 52 Bakers' roofs were quite different in form to the early Fox Henderson roofs, most notably in the greater use of cast iron and the much greater spacing of the frames – up to 30' (9.14m) as opposed to 12' 6" (3.81m) — transferring the load from the CGI sheeting to the frames through extremely light trussed purlins. It was in the design of the latter that the only certain evidence for the involvement of the Royal Engineers in these buildings' detailed design is identifiable. Following experiments on the breaking weight of the purlins these were found to fail with a pressure of 7,410lb when 7,980lb was required:
Sir William Denison therefore considered it expedient to strengthen the trusses by increasing the section of their centre tie-bears, and by adding to the thickness of metal in the cast iron traps, a course which in obedience to his directions has been pursued. 53
A complete technical description of the Baker Roofs over No. 3 and No. 4 slips at Portsmouth survives. 54
Deptford Dockyard Slip Roofs Nos. 1-3: 1844-1845
Deptford Dockyard Slip Roof No. 1 was built in 1844-5, 55 with completion occurring on 23 May 1845. 56 Unfortunately this roof was completely demolished following the closure of the Dockyard, and it is known now only from an engraving of c.1869 (Fig. 8) and from its foundation piers recorded during large scale archaeological excavations in 2011-2012.
The contract for constructing the iron slip cover roofs over Slips 2 and 3 in Deptford Dockyard (now the Olympia warehouse) appears to have been signed in October 1844. The building appears to have been erected in c.1844. The earliest illustration of the building is an engraving of c.1869 (Fig. 8). Subsequently, the roof of the building appears to have failed in the 1890s and been largely rebuilt.
The single internal area of 15,328' 1" (4,672m) comprises of an oblong 246' (75m) wide (east to west) by 203' (62m) deep (north to south) rising to a height of 56' 5" (17m) at its peak with (now) 33' 9" (10m) clearance in the main bays and 18' (5.5m) high at the eaves. Archaeological evaluation trial trenching in 2010 revealed the existing floor level to be 1m (3' 3") higher than in 1845. The original roof constructs were supported on cast iron I columns (Fig. 9) with flat capitals (totalling 24 in three rows of eight with three columns embedded in each of the end walls) and comprised two wide central bays 91'10" x 203'5" (28m x 62m) which covered the two slipways together with narrower side aisles 29' 6" x 203' 5" (9m x 62m) to the east and west to form covered working areas. The roofs and upper walls of the bays were originally wholly finished in CGI cladding. The upper walls of the north and south elevations are still clad in this material, though it is uncertain how much, if any, of this fabric is now original. Each of the north and south elevation upper walls were lit by windows. The engraving of c.1869 suggests that each end wall was lit by twelve windows (five upper and seven lower) whereas today the south elevation is lit by ten windows (four upper and six lower) and the north elevation by nine windows (four upper and five lower).
A photograph of c.1871 (Fig. 10) shows four upper windows plus a further blocked window and seven lower windows to each bay of the north elevation and it can be concluded that while the existing windows are probably original, two windows (one upper and one lower) have been blocked in each of the south elevations and three windows (one upper and two lower) have been blocked in each of the north elevations. The c.1871 photograph shows a further fourteen windows in the lower removable screens of the north elevation. These screens were taken down during ship launches.
The form of the building's roof has now been completely altered and originally was steeply pitched as is shown in the engraving of 1869 and the surviving Baker roofs at Chatham (Fig. 11). This is also clearly indicated in the internal photograph of c.1871 (Fig. 10).
As is shown in a photograph of pre-c.1913 (Fig. 12), the roof framing of the two central bays was replaced with a wrought iron tied arch roof 57 with riveted plate gussets. 58 The latticed trusses of the replacement roof are approximately 4' 11" (1.5m) at the apex, widening to 6' 7" (2m) at the supports. The context of this rebuild may be the conversion of the Dockyard to the Foreign Cattle Market in 1871 by Sir Horace Jones (1819-1887) but the photographic evidence (Fig. 10) might suggest otherwise. 59
However, the spans to the aisles and longitudinal bracing are largely original and closely match those observed in Slips 4, 5 and 6 at Chatham Dockyard. The cantilevered trusses to the side aisles are made from single castings with a straight top, curved lower boom and uneven pattern of lattice work. These trusses now rest on a steel wall plate resting on steel posts set in the outer walls.
Eleven angle/T section purlins span between the trusses in the central bays, three over the side aisles. Fourteen out of twenty-one original haunched longitudinal trusses remain, some 4-4.3m high. These have a ribbed lower flange, cast iron struts and wrought iron tie rods. The external appearance of the roof as originally rebuilt is shown in a photograph of 1947 (Fig. 13). Subsequently the roof cover has been entirely replaced.
The four lower sides of the building were originally completely open as is shown in the c.1869 engraving. Subsequently the south, west and north sides have been bricked up (the west possibly in part by c.1913 and the remainder by 1982 but with more recent rebuilds and additions). The cladding of the east side is in a modern profiled sheet metal fabric which also now forms the roofing material. Internally four cast iron wind braces are attached to the north and south walls; these are curved and include wrought iron elements.
Direct observation by the author of the surviving Baker roofs (Deptford Slips Nos. 2 and 3, Chatham Slips Nos. 4, 5 and 6) and the surviving drawings of all their slip cover roofs, including the preliminary unexecuted versions (Figs. 14 and 15), show these to form a distinct 'family group', with common design traits, standardised prefabricated parts, and little indication of any evolution in design over the two year period in which they were constructed. The surviving Baker roofs are recognisable as the work of one design team despite the severe mutilation of the Deptford example. Unfortunately the names of the civilian designers of these roofs are now unknown. 60
As well as the advantage in frame spacing enjoyed by the Baker roofs over the first four roofs constructed by Fox Henderson, there was another advantage; each pair of Baker roofs cost approximately £1,000 less than each pair of Fox Henderson roofs. 61, 62
Woolwich No. 4: the last contractor-designed slip cover roof?
After 1847 Baker and Sons were to receive no more new commissions for iron slip cover roofs following a near disaster in the construction of the Chatham roofs, though this was unrelated to the quality of the roofs themselves. 63
Fox Henderson however was to receive a commission for a further slip cover roof over No. 4 slip in Woolwich Dockyard. All discussions on the contract appear to have been managed by the Admiralty Works Department's civilian Architect William Scamp rather than Royal Engineers Superintendent Beatson. 64
The new slip cover roof was erected in 1847-8 and introduced an apparently completely new design devised for Fox Henderson by Edward Alfred Cowper (1819-1893) who had joined Bramah Fox in 1841. 65 Cowper stayed with the company until 1851 becoming Chief Designer and draughtsman under Fox. Cowper was to use his drawings of slip cover roof No. 4 at Woolwich Dockyard as a demonstration of the principle behind his design for the iron and glass roof of Birmingham New Street station which had a span of 212' (64.6m) and length of 840' (256m). 66
However, surviving photographs of Deptford Dockyard of c.1871 indicate that there was a wooden slip cover roof over Slip No. 5 of very similar form to the iron Woolwich slip cover roof No. 4, at least as viewed from the south east (Fig. 16; see also Reference 4, Fig. 5.14, p.100). This stood alongside and to the east of a more traditional wooden slip cover roof (Deptford No. 4), similar to the surviving Chatham slip cover roof No. 3.
The dimensions in plan of the wooden roof over Deptford No. 5 slip were 240' (73.15m) by 82' (25m) for the central span. These were recorded during a large scale archaeological excavation in 2011-2012. The evidence suggests it is possible that the wooden slip cover roof to Deptford slip No. 5 served as a model for Woolwich slip cover roof No. 4. This is consistent with Fox Henderson's approach to design on their earlier roofs, which were all based on wooden originals.
Slip cover roof No. 4 at Woolwich comprised a twelve frame building and was on a significantly greater scale than Fox Henderson's four earlier slip cover buildings, measuring 312' (95.1m) by 144' (43.9m) with a clear central span of 86' (26.2m) with the central space having a headroom of 58' (17.7m). The original 1847 portal frame was a structure of two tiers of roof with high level clerestory windows, louvres and a raised central lantern. In the construction of its frame it was a sophisticated and significant departure, using rigid framing or bracing through stiff joints. Cast iron framed aisles buttressed the tall nave, with wrought iron roof trusses incorporating tapered open work struts, possibly the first use of this type of iron component.
Again the detailed design and execution of this building was entirely Fox Henderson's. However, at £17,000 the cost of the building was more than that of the company's two first slip cover roofs at Pembroke, with the final cost representing an approximate 33% increase on the original estimate. This building still survives as 'The Boilershop' now converted into a retail outlet as part of the new Chatham Dockside complex (Fig. 17). 67
The final iron slip cover roofs: 1852-1858
By 1848 sixteen iron slip cover roofs had been constructed, of three basic designs with the most technically advanced being Fox Henderson's No. 4 slip cover roof at Woolwich Dockyard. No new slip cover roofs were built for four years. In 1850 Godfrey Thomas Greene (1807-1886), a retired Honourable East India Company Army Engineer, was appointed Director of Admiralty Works. In 1852 Greene, together with his assistant William Scamp completed the drawings for slip cover roof No. 7 at Chatham Dockyard. Drawings with specifications for this building were signed by Greene on 16 July 1852. 68 The design rather than being wholly new drew heavily on Fox Henderson's No. 4 slip cover roof at Woolwich, which as we have seen may have been inspired by the wooden No. 5 slip cover roof at Deptford.
In September 1852 Greene invited tenders and the contract to construct the building was won by 'Henry Grissell and Martin de la Garde Grissell of Regents Canal Iron works, … City Road, Engineers and Co Partners'. 69 Henry Grissell (1817-1883) and his brother Martin founded the Regents Canal Ironworks, Eagle Wharf Road, Hoxton in 1841. The works was located on the south side of the canal toward the City Road which is sometimes given as their address. Henry Grissell had been an apprentice and then assistant of John Joseph Bramah; he was noted for his technical knowledge and the Regents Canal Ironworks was noted as a 'test bed' for experimental ironwork. Although the design of slip cover roof No. 7 at Chatham has been ascribed to Greene and his Director's Office design team, in fact, when compared with Grissell's Sheerness Smithery of 1855-6 (now lost but recorded in a photograph of 1956) 70 and the surviving Sheerness Boat Store by Grissells' it is clearly part of a 'family' of buildings, which can be attributed to Grissell.
Although there is no documentary or drawn evidence to support it, there must have been extensive preliminary discussions between Greene and his design team with the subsequent building contractors before the design drawings for the building were finalised. This would fit well with Greene's approach to tendering in which only selected contractors, principally Fox Henderson and Grissell, were awarded contracts while others such as the Bakers were excluded. The implications are that the design of this building, although executed under Greene's direction were, in fact, as much the product of the contractors as of Greene and his in-house design team.
The last iron slip cover roof was also 'designed' by Greene and was originally erected over Slip No. 5 at Woolwich. Authorised in 1856, it was erected in 1856-58 by Grissell's, extended 1859-60 and subsequently moved to Chatham after 1869. It has been subsequently demolished. This building closely paralleled slip cover roof No. 7 at Chatham but with minor changes of detail; the main trusses were simpler and the knee braces below the bracing beams in the side were omitted. The building was 290' (88m long), and spanned 142' (43m) overall with a centre span of 82' (25m). A travelling crane was incorporated. 71
The Deptford and Woolwich iron slip cover roofs represent a fascinating period of rapid technical change. The creation of the first iron slip cover roofs was driven by economy and safety concerns, particularly the risk of fire. Happily iron technology had already reached a level whereby in 1842 the Admiralty could dictate that all new slip cover roofs should be in iron.
During the dominance of the Admiralty Works department by the Royal Engineers it is apparent that the detailed building design of the iron slip roofs was wholly decentralised. This explains the complete divergence in design between the iron slip cover roofs executed by Fox Henderson and those by George Baker and Sons. The former were clearly based on the pre-existing wooden slip cover roofs while the later owed much to contemporary railway architecture. Neither owed very much to the Royal Engineers except the broadest of dimensional specifications, and some minor technical details, facts which the Royal Engineers fully acknowledged in contemporary papers.
As Weiler stated:
The evidence suggests that previously [before 1850], major innovative works in iron were not designed in the Director's office with plans and specifications prepared in full detail before going to tender. Generally, engineering contractors did most of the important designs, although some were done by engineer officers in the dockyards. 72
The deployment to the Royal Dockyards of the Royal Engineers as supervisory officers in 1837 was an economic measure in a period of financial retrenchment. It was not based on the possession by the Royal Engineers of superior technical skills or experience in comparison with their civilian colleagues of the Admiralty Works Department, or of the civilian contractors engaged in iron construction. The skill sets amongst the Royal Engineers supervisory officers both as designers and project managers were variable, with Henry Brandreth being exceptional rather than typical. Ill health may well have prevented Brandreth from achieving significantly more in the way of systemised prefabricated iron construction during his time as Director of Admiralty Works.
In the period 1837-1850 project direction was almost wholly decentralised, and iron buildings directly designed in detail by the Royal Engineers could prove failures, as with Roger Beatson's Boatstore No. 6 at Portsmouth, 73 while those designed in detail by civilian contractors were largely successful. The most significant iron buildings constructed in the Royal Dockyards 1844-1848, the slip cover roofs, may have been conceived by a civilian contractor in 1840 and all of the detailed designs were by civilian contractors.
Only from 1850, as the role of the Royal Engineers in the Royal Dockyards declined, did a regime of centralised planning, project management and building design re-emerge under Godfrey Greene. The patronage by Greene of favoured contractors, in particular Fox Henderson (to 1856) and Grissell meant that their influence on building design was profound if understated. Research and fieldwork indicate that the majority of the buildings 'designed' by Greene can actually be attributed according to their civilian contractor, or other civilian designer.
Andrew Skelton BA ACIfA is a part time archaeologist and historian. Andrew is a co-author of a paper on Deptford Dockyard and a contributor to a paper on the Forge, Millwall and Paynes and Borthwick Wharves, Deptford.
Caroline Butler BA MSc ACIfA is an archaeological and heritage consultant and is currently advising on proposals to redevelop the former Royal Dockyard at Deptford.
Duncan Hawkins BA (Hons), MSc, FSA, MCIfA is a company director and archaeological and heritage consultant. He is currently advising on proposals to redevelop the former Royal Dockyard at Deptford. Former projects include work on various parts of Chatham Dockyard, the site of the East India Company's Deptford Dockyard, The Forge, Millwall, and Penn and Son's Boilerworks at Paynes and Borthwick Wharves, Deptford. Duncan is a co-author of a paper on Deptford Dockyard and co-author of a paper on the Forge, Millwall and Paynes and Borthwick Wharves, Deptford.
Notes and references
1. Sutherland, R J M (ed) 1997. 'Shipbuilding and the Long Span Roof in Sutherland Structural Iron 1750-1850 studies' in History of Civil Engineering, Volume 9, p 133 Table 1
2. Lambert, A 1991. The Last Sailing Battlefleet, Maintaining Naval Mastery, 1815-1850. Conway Maritime Press Ltd, London pp 37, 118-123
3. Sutherland, R J M 1997 op cit, p 127
4. Coad, J G 1989. The Royal Dockyards 1690-1850, p 110
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11. Ibid p.50-51, Plate XI
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17. Williams, M 1847 op cit, p 51
18. TNA, ADM 1/5521-1842
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25. TNA, ADM 12/370 24/10/1840
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28. TNA, ADM 1/5521-1842
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41. Ibid, pp 85-127
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47. TNA ADM 181/55/1844-45
48. Cumberland, F W 1847. 'Iron Roofs erected over Building Slips, No. 3 and No. 4, in Her Majesty's Dockyard, Portsmouth'. In Papers on subjects connected with the duties of the Corps of Royal Engineers, Vol IX (paper originally dated November 1846), p 59
49. TNA, ADM 12/444-23/9/1845
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54. Ibid, pp. 60-65, Plates 8 and 9
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64. TNA, ADM 12/460-6/5/1846-24/12/1846
65. Coad, J 2013 op cit, p 192
66. Proceedings of the Institution of Civil Engineers, vol XV, 1855-56, p 264 ff
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