Engitect Issue 2

All Change at Waterloo Station - Frazzi Blocks - "Kleine" Floors - The Bells Rang Out - CDM and All That - Waitrose Salisbury - Partnership News - Road Scrapings for Mortar - And Finally...

ENGITECT

Issue Two - Winter 1997

Introduction

Welcome to the second edition of the Hurst, Peirce and Malcolm newsletter. Our aim is to keep in touch with our clients and fellow colleagues in the construction sphere and to build on relationships which in some cases extend back to the 1920�s.

We were gratified to receive over 20 written responses and many more verbal compliments about the first issue. We hope the standard has been maintained for the second issue which we hope you will find interesting and informative.


All Change at Waterloo Station!  

Users of Waterloo Station will be aware that construction activity in, around, and beneath the station has been nigh on continuous for the last decade. Work to develop the International Terminal for Eurostar and the construction of the Jubilee Line tunnels and platforms beneath the station complex has meant hard hats and fluorescent vests have been a common sight on the main concourse. However, it is quite possible that even regular commuters may not have appreciated that another multi-million construction contract has been recently completed before their very eyes! This work involved a major (�23m) refurbishment of the 3 to 4 storey Edwardian offices which line the concourse including the retail accommodation at platform level.

Waterloo Station facadeWaterloo Station was first developed in 1848 when the terminus of the London and South Western Railway was moved from Nine Elms to a more central location not far removed from Westminster. The station platforms are raised on a series of masonry arches which are in themselves the culmination of a viaduct comprising nearly 300 arches and extending almost as far as Clapham Junction.

 By the early 1900�s the station facilities were overcrowded and a major expansion scheme was developed based on studies of railway termini in the USA. The work was phased for financial considerations and involved re-constructing platforms adding new ones and building new office accommodation which eventually realised a building some 800� (243 metres) long.

Work on the office building commenced in 1909 at the south eastern end of the concourse. The front and gable walls are of loadbearing Portland stone ashlar work backed with fletton brickwork. The walls to the concourse elevation are of facing brick with stone dressings including a large stone cornice at second floor level.

The fireproof floors consisted of Frazzi hollow unreinforced clay blocks spanning between the lower flanges of steel beams. Timber joists were arranged to span on to the steel beams to support floor boards. In most cases the Frazzi blocks were topped by 3" of concrete to provide a degree of fire protection to the timber floors. (For further information on Frazzi systems, see 'Frazzi Blocks' below).

The floors are supported on internal steel stanchions with steel grillage foundations, themselves placed on massive brick piers, punched through the earlier arches, and extending down up to 10 metres in to the marshy ground beneath the station. Internal office walls were built up in hollow clay blocks.

Work continued in phases working northwards with a general suspension of activity during the Great War. The final stages constructed immediately following the War encompassed the well known Victory Arch which now stands proud at night under floodlights. Different materials were introduced to the floor construction suggesting that there were difficulties in obtaining items in the aftermath of the First World War. These floors comprised the Kleine system with hollow clay blocks, 6" wide and 10" long, long laid and jointed in cement mortar reinforced with a thin steel strip. (For further information on the Kleine system see overleaf).

Waterloo Station Front Elevation

During our initial surveys we found the building to have been largely untouched apart from Bomb damage inflicted during the Second World War.

Refurbishment work comprised the removal of all timber floors, partitions and some brick walls. Three new lift and stair cores framed in structural steel work were formed, the floors were strengthened to a specification in line with contemporary office requirements together with the insertion of a full air conditioning system.

The work was carried out under a design and build contract led by Bovis Construction Ltd with Wilson Mason & Partners providing architectural input and Hurst, Peirce & Malcolm responsible for structural engineering matters.

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Frazzi blocks 

Frazzi flat terracotta lintel system

The Frazzi system is just one of the types of terracotta fireproof flooring introduced in the late 19th century. The difference from the other systems was that the components were made in Cremona in Italy, from where they were imported, and the clay there enabled them to be extruded with much thinner walls than similar native products.

 Frazzi invariably used "joist covers" to enclose the bottom flanges of the filler joists and provide bearings for the flat or arched lintols or tubes spanning between them. Frazzi also provided 23 mm. thick cellular blocks with tongue & groove joints for fireproofing stanchions.

We have seen Frazzi floors in building dating from the 1890's up to the First World War, but not later, even though they were still advertising in the mid-1950's with an invitation to apply to their office in Norfolk Street, Strand for a brochure. We would be interested to hear of any Frazzi floors after 1915 seen by our readers.

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"Kleine" Floors

Kleine was another type of fireproof flooring incorporating terracotta blocks, but dispensing with iron or steel filler joists and using steel strip or rods between the hollow blocks as tensile reinforcement, in conjunction with the concrete topping. Kleine floors were first used in this country in 1906 and the early floors incorporated hoop iron or steel in the mortar joints between the hollow clay blocks. In later floors the lines of blocks were spaced out to form concrete ribs between them, in much the same way as the hollow pot floors most of us remember, which continued in use until London Brick ceased to produce hollow tiles in 1984.

Unusually there was no structural concrete topping with the Kleine floors at Waterloo. Load tests on the floors above near Victory Arch at Waterloo found it capable of sustaining loads equivalent to contemporary specifications albeit lacking in overall robustness and resistance to concentrated point loads.

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The Bells Rang Out

The bells of St Mary Magdalene, Cowden, East Sussex rang for the first time in thirty years recently as part of an exercise to assess what would need to be done to the fourteenth century oak timbers of the entirely timber framed tower and spire to enable the bells to ring in the next millennium.

The 127ft spire was notorious for swaying during ringing. Full circle ringing stopped in the 1960's when the timbers were found to be weakened by decay and death watch beetle.

As part of the investigation, movement of the tower was monitored during the ringing with accelerometers to determine the natural frequency and modes of the hollow pot floors most of us remember which continued in use until London Brick ceased to produce hollow tiles in 1984.

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CDM and All That

Lawrance Hurst was glad all Hurst, Peirce & Malcolm's appointments as planning supervisor are in the UK when he recorded this activity during his summer vacation.

Readers are invited to forward suggestions as to what the man in the foreground is saying to the decorator perched so precariously at eaves level!

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Waitrose Salisbury

Waitrose Ltd., part of the John Lewis Partnership, recently opened their new Food and Home Store in Salisbury. The store is only the second of its kind within the John Lewis Partnership to combine food, clothes and home style items. It is located on an island site within the flood plain of the River Avon with the main river running to the East on a branch stream, Summerlock Stream to the West.

Although the site had previously been a cattle market the Environment Agency insisted that the development should not affect the existing flooding situation. This meant demonstrating that in a 1 in 100 year flood, flood levels upstream and downstream will not change once the building is complete. Initially, this lead to the development of a scheme of extensive flood alleviation works upstream of the site. However, by refining the hydrological model for the River Avon, it was possible to show that much smaller flood alleviation provisions would suffice, much to the relief of the local residents who did not want flood banks built across their local green.

Hurst Peirce & Malcolm were asked to design these works in conjunction with assistance from hydrological consultants. The final scheme included a flood relief culvert through the site and automation, with remote control, of a rising sector flood gate which provides the main control of the river level through Salisbury. In addition, environmental works were carried out to improve the river margins upstream of the development and water margin control facilities were provided to a set of reed beds in an area of scientific interest to prevent them drying out. The local children now have a �dipping platform� where they can sample the water of the River Avon for aquatic life.

We are now advising Waitrose on the complications of developing a site at Cheltenham which is also in a flood plain, where the River Chelt currently passes under the proposed development site in an old brick culvert.

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Partnership News

We would like to welcome three new members to our technical staff. Mark Dicks who joins us from Waterman Partnership as Senior CAD Technician, Mrs. Alex Elliot who has just graduated from the Royal Military College of Science, Shrivenham as a Graduate Engineer and Michael Chung who has just graduated from Trinity College, Cambridge also as a Graduate Engineer

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Road Scrapings For Mortar

Readers will recall the back page article from our last issue where the 19th century practice of using road scrapings (sand laid on metalled surfaces to prevent horses� hooves from slipping) and ash pit refuse for mortar and plaster was described.

Confirmation of this practice in Victorian London comes from Johnny Johnson, whom many of our readers will remember as Hillier Parker�s Chief Building Surveyor for more years than he or we care to remember.

In 1951 Johnny was refurbishing three houses in Cromwell Road originally dating from 1874, opposite the Natural History Museum, for the Canonesses of St Augustine. The back additions had to be demolished because of an extensive attack of dry rot with which the brick walls were found to be riddled. This had started with dry rot in timber lintols and had travelled up to 20 or 30 feet through the brickwork to internal timbers, fed by horse manure in the road scrapings used as aggregate for the mortar in which the bricks were laid.

Knowledge of practice � good and bad � used by our predecessors in the building industry is usually interesting, sometimes useful, and, as in this case, can provide the answers to questions that modern analytical methods would find inexplicable.

This same theme is continued in the strip cartoon below, which confirms the use of other dubious materials. It comes from a book originally published in 1880.

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And Finally...

To continue our theme on 19th Century building practices, here is an article taken from the Complete Builder by J. F. Sullivan published in 1880.

Readers may empathise with the building owner as speculative housing of this date was built to the least possible cost using materials of questionable quality.

  The Mud Wall of Conceit