Building the New Palace: A Watery Challenge
I don’t often write about the new Palace of Westminster, because I think it’s had a lot of attention over the years, and can stand up for itself. I prefer to blog about the old Palace because far fewer people know about it, and I remain fascinated by the great hole in our knowledge about it. However, on this occasion, I’m making a rare exception to explain an aspect of the construction of the new Palace.
The footprint of the old Palace was under two-thirds of that occupied by the new Houses of Parliament today. The eastern (ie river side) wall of the old Palace buildings would only have reached as far as today’s central lobby (about half its current width). Charles Barry’s ambitious plan extended his giant new building over the gardens on the eastern side and beyond the shoreline of the Thames, so that the new Palace was built right out into the water. Subsequently the embankments north and south of the Palace did the same, to accommodate Bazalgette’s great sewerage system for London. As anyone who has sailed down the Thames past Westminster will tell you (including those in the recent Diamond Jubilee River Pageant) the creation of embankments on either side of the Thames has narrowed it and speeded up the current very considerably. Navigating a small boat downriver through the arches of Westminster Bridge these days is not for the faint-hearted.
To construct the riverwall and the foundations for the eastern flank of the new Palace, including the terraces and dining rooms on the ground floor, and above them, the two great libraries on the principal (mezzanine) floor, and the committee rooms on the first floor, the engineers had to building an enormous cofferdam to hold back the Thames. Test borings began in 1837, and the cofferdam itself was designed by Charles Barry and Walker & Burges, the civil engineering company, with construction being let to the firm of J & H Lee of Lambeth.
The cofferdam was a watertight box (a technology later replaced by the caisson more familiar today) made of two walls of tight layers of timber cladding ten feet apart, the gap between them filled with wet clay from the river bed which prevented the water seeping through. The whole construction, begun on 1 September 1837, was 920 feet long, connected to the walls of the old Palace’s wharves at the north and south ends. A ten-horse power steam engine was used to pump the water out, and then keep it out, creating a dry plateau where the river wall foundations and then the terraces and Palace walls could be built. It also accommodated the contractor’s workshops. It was the largest cofferdam ever seen at the time and was in position for 12 years. Excavations for the new Palace began there on 1 January 1839, it having taken 16 months to build.
Further reading: Denis Smith, “The Techniques of the Building”, The Houses of Parliament ed. M.H. Port (Yale UP, New Haven and London, 1976), pp. 195-197.