What is an oast house?

A question we get asked from time to time is, what actually is an oast house?

For us, there couldn’t be a better symbol of Kent than an oast house. Their striking shape dots the countryside skyline, providing some Instagram worthy shots – but what exactly are they?

In a nutshell, an oast house or hop kiln is a building created to drying hops as part of the brewing process.

Oast houses or hop kilns have played a huge part in the agricultural history of both the county and the country. And, at the heart of their fascinating origins is one of the nation’s favourite tipples – beer!

Starting from the top, what are hops? Hops are the flowering clusters of a plant called Humulus Lupulus and they give beer its distinctive flavour and aroma. Like grapes in wine, hops come in different varieties, each with its own characteristic. For centuries, the garden of England produced hops on an industrial scale, bringing life and prosperity to the countryside – and building on mass the oast houses seen all over Kent.

Side note: If you want to know a bit more about Kent’s oast houses, please have a read at our previous blog post.

Ok, but what do hops have to do with oast houses?

After enjoying a long summer basking in the English sunshine (in theory), hops are harvested around September. But, before they can be popped into any brews, they need to be dried. That is where the oast houses come in.

When hops are picked, they have a moisture content of 80% – which is no good for brewing. However, after an oast house has worked its magic, the amount of moisture in them goes down to a tiny 6%.

oast house history

How did a traditional oast house work?

Sitting on the ground floor of the roundel was a furnace, halfway up the tower was a slatted ceiling covered by a horsehair cloth, then above that a cone-shaped roof, and at the very top a cowl.

First, the hops were placed across the slatted ceiling. The furnace was then lit, and as the heat rose through the slatted ceiling, moisture was removed from the plants. The excess steam rose through the conical roof and out through the cowl. Not only did the cowl act as a very effective vent it was also rotated by a wind vane, ensuring that air was always circulating throughout the roundel and that the hot air had a clear path out of the oast.

Henden Manor Oast Cowl image

After the hops were deemed to be dry, they were shovelled out and placed onto the barn floor to cool. Once ready to be packed, they were pressed into large jute bags and sent to market. Just like today, brewers would not just throw any old hop into their beer so, by law, each batch was labelled with the grower’s details. This ensured that the much-loved Kentish beer would never be compromised.

As the hop growing industry in Kent declined and imported hops fell into favour, the use of oast houses declined too. Now, many of these wonderfully clever contraptions have a new lease of life as beloved homes!

Dude & Arnette are the UK’s market leader for oast cowl manufacturing, restoration and repairs. We have been the go-to family business for oast house owners since 1937.

Sue & Les Hart - Cowl