C O N T E X T 1 3 4 : M A Y 2 0 1 4 25 the introduction of RSJs would be the normal approach but at Mount Stewart the ceiling below usually has cornicing and often heavy plasterwork. To remove or replace these would be prohibitively expensive, and could not be further from the minimum intervention approach we usually take in conservation. Necessity truly is the mother of invention: structural engineer Jon Avent of MannWilliams designed a unique floor-strengthening system, ingenious in its design and simplicity. I had the privilege of working closely with Avent in the fitting, trial testing and evolution of the system, which works by placing tension into the floor via a truss system of threaded bar and linkages placed between the joist bays. It is fitted from above, with the only intervention being the lifting of floorboards. The system provided stiffness improvements and recovered deflection. Performance improvements of up to 40 per cent were achieved where the system was adopted. Crucially, there was no damage to the ceiling below. Where required, the system is now being rolled out in the first-floor bedrooms. The house’s quality of building makes one ask: ‘why on earth did they do that?’ The stud walls, which are mostly on the first floor, are generally built straight on top of a single joist. Considering the joists (305mm x 50mm, or 12"x 2") span a total of 8.22 metres (27 feet), we often wondered why things still stood. I believe that what saved the house, or certainly the ceilings, is the excellent quality of the longleaf pine (pitch pine) used. The visual joinery in Mount Stewart is often stunning. The best example of craftsmanship is to be found in the floors of the Music Room and in theTemple of the Winds.The original work, carried out by a Belfast man, John Ferguson, is of the highest quality in comparison with the few other Irish houses to have inlaid floors. Two floors stand out for reasons of technique and beauty, both presenting challenges in their conservation and restoration. The first is in Lady Londonderry’s sitting room. Designed by Dance, it is a suspended longleaf pine floor inlaid with bog oak and holly bands in a unique pattern.We needed to lift sections to facilitate cable and pipe runs. This floor was the one I looked forward to lifting as it was complex, and needed much care and attention. At no stage would I have allowed it to have any major interventions or be roughly treated. The floor, and most crucially the bands of bog oak, had, however, been disrupted in the past by over-zealous electricians. Thankfully they limited their activities to just two routes, leaving the majority of the floor and the exquisite centre piece alone. The floor is secret-nailed with flooring brads and an oak peg between adjoining boards at 305mm (12") centres. Thanks to the heavy-handed workmanship of those electricians, I had an entry point into the floor. The bog-oak inlay had cracked and separated over the years into small sections. In some places it had been glued down rather crudely. To take the bog oak and holly strip up, I had to rebate a section of timber. The rebate was equal to the width and length of the section being removed, so when lifting a section it could be placed into the groove, keeping it all together and protected from any further disintegration. In this state, any conservation work needed could be carried out. The second floor of importance is in the Saloon, which was originally a grand function room, with a gallery and a domed skylight, designed by William Vitruvius Morrison in the 1850s. It has a suspended, quarter-sawn oak floor laid out in a quadrant style, with boards radiating from a central point. The floor had been disturbed in the past (those pesky electricians) so it was possible to inspect and lift the floor using the existing access points. What became immediately apparent was that instead of there being oak dowels, metal dowels had been used. Having metal dowels and being secret-nailed, the floor would be a real challenge to lift. To separate the boards without causing any damage, a metal bracket was specially made from 3mm steel plate, 100mm wide, with an end bent round 90 degrees. It fitted in the gap between boards and gave me something MannWilliams’ floor strengthening system for the over-spanned joists Timber decay in the joists of the Saloon
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