Victorian Greenhouse Restoration
           
My first Victorian greenhouse restoration was the restoration of what is known as a stovehouse or hothouse which once formed the west wing of a Victorian Conservatory Glasshouse built of teak. The complete structure originally extended to almost 90ft in length and is located along the southern perimeter of what was once the vegetable garden at Winsford Walled Garden. The stove wing itself measures 28 ft long by 19 ft wide rising to 12ft at the ridge. The opposite wing, located furthest from the boiler house was the temperate wing containing an entirely different internal arrangement. Between the two was an octagonal fern house which was removed by US Forces who used the gardens and the surrounding estate before the Normandy landings.
The stove house has a central partition, within each identical half are two brick-built growing beds on either side of an ornate cast iron central bench.During the summer of 1999 it was obvious to anyone who saw the stove house and the multitude of roof props inside that the next winter would be its last unless something was done to preserve it.
Restoration work begins
Our first task was to uncover what was there. To identify what could be retained and remove what was irretrievable. While I removed the soil from the growing beds, Aileen removed the rubbish in the central duct beneath the benches. It took us three long days.
Initially, the greenhouse received two washes. The first wash removed the moss, dirt and slime from the wood. The second cleaned up after the first. All the 'quality' glass was removed after the wash down and set aside to be recycled.
There were several key structural problems due to various short cuts taken by previous owners in the past and these were overcome and corrected by rebuilding the corners and rebuilding about 95% of the roof. To this day, I have never seen a greenhouse with a higher degree of ornamentation and ingenuity than the Foster & Pearson greenhouses at Winsford Walled Garden. Fortunately, the ornate original Victorian cast iron work was retrieveable. Then it was taken back to the bare metal and repainted.
A typical example of the manufacturers’ attention to detail were the zinc inserts set at a downward angle into the top of each door frame (there are four doors). These prevent condensation dripping beneath the frame and remaining as a pool of water on the top of the door until the door is opened.
Ingenious Heating Design
Running the length of the greenhouse is a central duct that originally contained the 4 inch diameter primary heating pipe work, which exited the stove house and ran through to the other sections of the Conservatory Greenhouse.
Beneath both central benches lying across the central duct are two galvanised steel water tanks of 150 imp galls capacity each, which were, and still are, used to irrigate and humidify the greenhouse. The tanks straddled the duct in order to benefit from the rising heat off the primary pipe work. In this way, heated plants were never chilled by cold water applied to their roots or foliage. The heated duct also contained the irrigation water supply pipe. As a result, the irrigation pipe never froze and always brought warm water to the greenhouse.
The benches themselves were covered in thick slate which retained a tremendous amount of heat to warm the terracotta pots resting upon them.
A slate bottom at the base of each growing bed hides the secondary pipe work that once heated the compost. A valve on each side of the greenhouse meant that one pair of growing beds could have a different soil temperature from their neighbours opposite. Coupled with the partition and individual venting this made for a very flexible growing environment.
An important by-product of the heated beds was their slow release of stored heat to the surrounding air. This battery-like behaviour helped to smooth out any thermal inclines. In the event of boiler failure they could be the difference between the survival of a rare and expensive collection and its complete ruin.
A third heating circuit used to rise up through the floor beside the growing beds and ran along the front of each. Its convected heat was designed to remove any roof condensation and the resulting damage to foliage that dripping condensation can bring. The removal of roof condensation also led to an improvement in light transmittance, especially during the winter. The pipe work continued along the floor towards the nearest end wall before rising up the side and along the rear of each growing bed. Effectively encircling the bed with a warm air curtain that could be adjusted to suit the foliage growing in each bed. This curtain also prevented condensation forming on the glasshouse walls.
On cold winter days when the windows and ridge vents were closed and the risk of botrytis high, cold air was still permitted to enter the hot house through a series of vents along the side walls. This cold air passes over the third heating circuit pipe work running along the outer walls and the fresh air is preheated before it reaches the warm plants.
Replacing the ridge ventilator
The greenhouse ridge had been covered in sheet steel and secured with 4” nails. Beneath this sacrilegious eyesore were found some fantastic examples of the Victorian engineers’ art in cast iron. The greenhouse ridge was not only beautiful, it could be raised vertically to exhaust hot air at the hottest point, along the full length of the greenhouse. After the sheet steel was removed the ventilator was completely rebuilt. Where there had been sheet steel now there was glass.
The ornate windless and worm drive used to raise each ventilator had seized solid with rust. These had to be gradually eased free, cleaned up and then two coats of paint applied. It took about thirty-six man-hours before both mechanisms looked like new.
Replacing the timber roof
When condensed water falls from roof glazing and drops on valuable plants, the resulting droplets act like miniature magnifying glasses, that can often lead to unsightly burning on the foliage. Foster & Pearson designed a new rafter with an integral drip which carried the condensed moisture down to the eaves and outside. The cross section of these rafters is quite complex for any wood machinist to reproduce. Which meant ‘prohibitively expensive’ from our point of view. Thus the replacement rafters are a simple design based on the original overall dimensions but without the integral drip.
size="3">Approximately 95% of the glass on the stove house was recycled from the site. But almost every one of the 600 glass panes had to be re-cut. It was filthy and at the time a bitterly cold wind blew from the north, the greenhouse (then) was very exposed but we made it in the end.
We began our restoration on the first day of September, 1999. The tender plants went undercover in the first completed partition on November 4, 1999. The first frost arrived two days later. The restoration was finally completed on November 15, 1999.
Restoration purists might argue against our use of simplified rafters and silicone sealer. But I would argue that such methods have enabled the preservation of a fantastic greenhouse that would otherwise be lost. Also, because it was teak, this greenhouse was never painted. It does not need painting. Yet modern glazing putty needs to be painted otherwise it breaks down under direct UV light.
As a result of our 3-month effort, garden visitors today can wander inside the magnificent restored greenhouses and witness Victorian horticultural engineering at its very best for themselves. A polite request allows visitors to work the windows and vents themselves. This is a far cry from my first visit to a restored Victorian greenhouse that could only be viewed from the outside.
The selected images highlight various Victorian Greenhouse Restorations completed at Winsford Walled Garden. These low resolution examples are taken from the Victorian Greenhouse Restoration Guide which contains 65 colour photographs, together with a very detailed step-by-step description of the work, together with advice on the most appropriate method of restoration together with recommendations for tools and materials. Mouse over for image description.
|
