The roof beams date the Tithe Barn to around 1480. It was a basic agricultural barn with seven bays. It has since been significantly modified, especially when it was converted to use as a school, in 1789.

The original barn was a single open space with no windows. Carts would have come through the two large central doorways directly opposite each other, with a porch on the north side and probably a matching one on the south side though no structural evidence of it remains. Large wooden double doors were attached to the stone entrance – you can still see some of the pintle hinges (one in the accessible toilet!).

The barn was probably used to store tithes – a 10% tax of the agricultural produce of local farmers collected by the church. Holy Trinity Church was built c. 1311 on the highest point in Nailsea. The central floor area of the barn would have been used for threshing – the grain was harvested ‘green’ and threshed as and when needed. The main crops in the area at that time were hay, corn, wheat and barley.

The barn was a very basic build, for a small, probably quite poor parish compared with some of the more elaborate tithe barns attached to wealthier parishes and manor houses (such as Barton Farm, Bradford on Avon). It is similar in style to West Pennard Court Barn in Somerset built for Glastonbury Abbey and now owned by the National Trust.

The magnificent roof of the barn reveals its medieval origins.  Most of the original structure remains. The exterior roof is now clay pantiles but was probably thatched originally, given the relationship between the rafters and the walls.

There are six arched-braced collared trusses along the length of the barn. These were a ‘kit of parts’ pieced together and probably cheaper and easier to source than simple cruck trusses made from a single piece of curved forked timber.

The rafters running down the inside of the roof are crossed by horizontal purlins. The curved wind braces were thought in medieval times to stop the whole roof racking (falling east or west) but calculations show they are not required structurally.

The trusses were originally constructed at ground level, then dismantled and reconstructed in their final positions – the carpenters marks are still visible that were used to match each piece as it was put in place.

Ventilation (to keep the crops from going mouldy) was provided by the repeating pattern of arrow slit windows and four putlog holes in each bay. The putlog holes were from scaffolding originally used in constructing the barn. They were probably left open for air flow. The triangular owl hole at the top of the east wall would have allowed owls in to eat any mice!