Case Study

Fire Defence plc has a wealth of experience in the more unusual fire sprinkler installations. After designing and installing sprinkler protection to Longleat House, Wiltshire, we were appointed to provide the same disruption-free service for a castle in the Hebridean Islands.

12 HOUR AND A FERRY CROSSING
Quite apart from the fact that it was some 12 hours and a ferry crossing distant, this ancient shooting lodge was a very different project from Longleat. The castle has evolved through the centuries, so that former exterior granite some walls two feet thick did not line up with new partition walls and needed to be broken through for our installation. Did the ‘grey lady’, the inevitable apparition said to float around the house turning lights on and off, also need our concern?

LACK OF FLOOR SPACE
The main hall rises the full height of the house, under a pitched glass roof. There are none of the usual huge voids. We lifted oak floorboards and parquet flooring to find joists laid on 15 inches of concrete supported by steel ‘H’ sections, installed after a disastrous fire a century before. There was only 50mm of space under the floorboards. To be able to install rigid steel pipe, some 90% of the floorboards would need to be raised. Given the thickness of the concrete, there was no easy way to fit ranges tight to the floor and screw in drops with concealed sprinklers on the end.

CONDENSATION CONCERNS
A further concern was the difference between the temperature of the outer granite skin of the house and the ambient temperature inside. How would the installation be affected, when the pipework within the exterior walls would be significantly colder than the spurs entering the floors? Would the result be condensation and subsequent corrosion?
The answer  to many of these initial problems was found in plastic pipe.
Plastic offers no corrosion. As it is semi-flexible, it allows use where rigid metal tube is impossible. There is no ‘turning’ requirement for joints. It could be slid under floorboards to save lifting them all. It permitted internal coverage of a spiral staircase and tower within the stairs. Approvals were checked and the containment of the pipe in floors ensured hanging was not a problem.

No oil-based paints could be used on exposed pipework. Metal sleeves had to be provided for pipework running through joists, to protect against piercing by the nails used to refasten floorboards. An extremely high level of cleanliness had to be maintained, to ensure that dirt or grease did not affect the correct bonding of the joints. Despite this, installation was quick, simple and clean (although the problems of supply and delivery to such a remote spot are another story.)

UNMARKED BEAMS AND JOISTS
Other issues still needed addressing. Routes for traversing the building were often convoluted and difficult to access. It was important to obtain the best visual aspect for the heads. To do so the sprinkler positions were marked out from below, and the ceilings drilled upwards to meet the pipework above. However, unmarked beams and joists and differing room layouts from one floor to another were discovered. Despite frequent measuring between known vertical reference points like walls and open fireplace flues, varying wall thickness and positions sometimes resulted in a need for our engineers to drill additional reference holes. Although later made good, actions like these can tend not to be fully appreciated in a building of this quality and history.

ALTERNATIVE TESTING EQUIPMENT
During the installation of pipework care was taken to mark each joint as it was sealed. Additional bracketing was installed in the roof space for support. Air vents were installed at high points, as well as drains at low points. It was necessary to be especially careful when the time came to test the system, as the techniques are slightly different from steel. A dry compressor had to be specially taken to the island, as the lubrication oil in our usual equipment could damage the plastic.

RESTRICTED WATER SUPPLY
In such a remote location the water supply can tend to be less than adequate, and so we installed a 75 cubic metre tank and pumps. Once more the harshness of the climate had to be considered and additional insulation and even an extra immersion heater was fitted.

THE GREY LADY CAN NOW SLEEP AT NIGHT
The project went well and proved the effectiveness of correctly selected modern materials and techniques. The maintenance contract has been effective and in two years there has been no emergency – merely the failure of an immersion heater. The grey lady appears not to have objected to these new safety precautions. Maybe even she can now sleep at night, knowing that the catastrophes once caused in the castle by fire can never be repeated?