Although we completed this commission shortly before the controversial demolition of Greenside, I now find it impossible not to link the project with my experience of serving as an expert witness at the recent Greenside public inquiry.
The contrasting fate of these two distinguished works by the gifted and inscrutable Colin Lucas seems to join the original divisiveness of Modern architecture with the struggles of its current conservation.
Both listed buildings, one is razed, while the other is now fit for an unlimited future.
Just as in the 1930s, radical buildings need brave clients. The commitment of the incoming owner to the rescue and regeneration of Frognal was exceptional. The house purchase was completed with only a hope that listed building consent for the necessary interventions would be forthcoming.
Of the three determinants of any building project, here programme and cost were treated as variables (within reason). The constant was quality. For my associate Amir Ramezani and I, this tenacious client aspiration was the crucial enabling factor in completing a conservation and upgrade project fraught with all the usual difficulties and more besides.
Though the accommodation brief was a good fit for the house overall, the search for an elegant synthesis with conservation objectives was not straightforward. Numerous permutations of the top floor in particular were tested in constructive discussion with English Heritage, before arriving at a resolution that we felt balanced operational and historical demands.
Our eventual strategic decisions included:
completely rebuilding the poolroom to differentiate it in plan and section from the main carcass; locating service rooms (which suited the high cill levels) along the noisy west side as a buffer zone; forming two good bedrooms from the subdivided spaces in the south-east quarter;
reconfiguring the master bedroom as a unique room facing south over its own terrace (the raised portion of the living room ceiling below);
retaining the corridor with reinstatement of its characteristic lens lights; and, most importantly for the retrieval of Lucas' original composition, retraction of the top-floor enclosure on the northern part of the street facade and its treatment as frameless glazing to recall the original terrace opening. (According to local anecdote, many people assumed 66 Frognal was actually a small apartment block with two flats each side of the central staircore, such was the misleading effect of the earlier alterations. ) Other moves were more subtle. Claiming a margin of the second-floor terrace for the master bedroom as a window-seat gives a new spaciousness to this room without increasing floor area. Introducing louvres by the living-room entry seeks to register the nuance of asymmetry in the status of the two nibs that results from the updated kitchen plan behind. The fireplace 'floating wall' helps anchor the living room, while disguising a maelstrom of services within - an architectural and engineering installation that involved coordinating five different contractor packages.
The staircore glazing is etched to within an inch of the frame to allow glimpse views out, while eliminating the need for curtains, which it was felt would corrupt the abstract quality of the street facade.
The biggest technical challenges were probably the achievement of adequate tolerances on the wildly irregular original envelope to establish workable lines and levels and allow window replacement without excessive shimming; devising suitable construction details despite the enhanced insulation, in order to retain the 'thinness' of original edges; and the usual puzzle of finding discreet ways of re-servicing the building comprehensively to current standards.
The proposition we hope to advance in this case, as in our Modern Movement conservation work generally, is that such projects can result in both a more authentic reading of an original masterpiece and a wholly viable property geared to 21st-century expectations of comfort, value and performance. Achieving one objective without the other might be easier, but would leave a conundrum unsolved and jeopardise sustainability, which is, after all, what real conservation surely entails.
John Allan, director, Avanti Architects