Fumigating a windmill is not something we do every day. This made the job carried out by our fumigation team in the Dutch town of Alkmaar this week particularly special: the complete fumigation of Strijkmolen C, a historic drainage windmill.
The oak windmill was built around 1630 and is one of four surviving drainage mills along the Molenkade, literally translated as ‘Mill Quay’. Originally, six mills stood here, identified by the letters A to F. Mill C has been damaged by fire twice and was rebuilt after each fire. Today, it is owned by the Molenstichting Alkmaar en omstreken, the regional windmill foundation. Although the mill no longer plays a role in water management, it is still in working order and is also used as a residence.
During a thorough inspection, evidence of wood-boring insects, including woodworm and longhorn beetles, was found in the heavy oak structural beams.
What makes these insects so difficult to detect is that their larvae can live deep inside the wood for years. They bore tunnels through the timber and can damage the structure unnoticed. Exit holes and bore dust are often the only visible signs of an infestation, and merely the tip of the iceberg.
Read our previous article to learn more about identifying, treating and preventing wood-boring insect infestations in timber structures and historic buildings.
Wrapped from base to cap
A surface treatment is not always sufficient for thick structural beams. The larvae may be hiding deep inside the timber, while not every side of the wood is accessible. Fumigation with sulfuryl fluoride was therefore selected as the most suitable treatment. The gas penetrates deep into the wood and is effective against every life stage of the wood-boring insects, from eggs and larvae to adult beetles.
Paul Wielinga, Team Leader Fumigation, explains: “We started the job last Monday. We wrapped the mill from base to cap in gas-tight sheeting and then put it under gas. The site was cordoned off and we remotely monitored the gas concentration for 48 hours. This allowed us to confirm that the correct concentration was maintained throughout the treatment.”
He continues: “Yesterday, we removed the sheeting, ventilated the mill and carried out the final measurements. By the end of the day, we were able to hand Strijkmolen C back safely and gas-free, allowing the miller to return home.”
The result? A structure treated against woodworm, longhorn beetles and other wood-boring insects. A special job at a special location, and a great achievement by our fumigation team!
Want to prevent damage to your timber structure?
Have your timber structure inspected promptly if you notice signs of woodworm or other wood-boring insects. Our specialists assess the nature and extent of the infestation and advise you on the most suitable treatment method. Contact us for a professional inspection and tailored treatment advice.
