Project Profile: Queens County Farm Museum Phase II

The first step was to determine the material to use for the restoration. Many materials were considered. Cypress is one that was used for many years in the construction of old greenhouses and conservatories. Readily available and high resistance to moist environments.

However a new timber product was favored, Accoya. This wood modification has outstanding durability, terrific dimensional stability and has a perfect surface for  Technos, a paint coating we used on the surface. Accoya wood modification is not a pressure treatment. It is a chemical modification of the wood itself. Unlike pressure treatment, in which preservatives such as ammoniacal copper quaternary compounds are infused into woodacetylation chemically modifies wood. In the process, acetic anhydride reacts with the hydroxyl groups on large molecules such as lignin and hemicellulose in the plant cell wall.

The result is a wood product that will literally last forever and never change its moisture content. This was a huge eye opener for the City of New York. Accoya has been widely used in Europe for years, but is just now finding its favor among designers, builders and architects in the United States. Now the material selected, the components of the greenhouses had to be carefully removed, categorized and copied. Like and architectural dig, each member was carefully measured and drawn to scale so the CNC machine that would copy the designs would create exact duplicates.

During a restoration project, especially a government project, the goal is to maintain the history of the structure. Ideally the material specified for the greenhouses would hold the historical significance. The Accoya frames will do just that, especially when painted the original color. The Accoya looks like it has withstood 100 years and will certainly withstand 100+ more.

When it came time to specify the make-up of the glass roof and side walls historical significance had to be tossed aside to public safety. The original roof frames were made to hold 2 layers of 1/8″ annealed laminated glass. Laminated glass works similar to that of a car windshield – if it breaks it won’t cause extensive harm. We felt very strongly that the glass, especially the roof glass, should all be tempered. Tempering the glass meant that the entire project would have to be modified to accept thicker, more durable glass. In the end current safety standards won over history.

All the the metal gearing and structural components had to be cataloged, removed and sand blasted before powdercoating and re-installation. Many of the components were missing and created quite a hunt for historic greenhouse parts in various ‘boneyards’ around the country.

The new structure had to be built exactly the same as the original or non of the gearing would work. Site measurements were taken once, twice and then again to make sure every part and partial would be an exact fit to the original.

Work began. These large piles of rough looking wood are actually the Accoya. We carefully create the image of the wood items to be made, enter them into the computer and the CNC takes these rough piles of wood and turns them into the finished product.

Three coats of Technos, shop painted and we are ready to install.

Next: Constructing the greenhouses.