Bat Mitigation at St Tewdrics House, Chepstow

On 11th January 2018, a bat mitigation check was undertaken at St Tewdrics and we were happy to see that the bat loft incorporated into the newly created wedding venue was in use. We found a cluster of lesser horseshoe bat droppings on the floor, as well as two newly built swallow nests! This confirmed that the mitigation put in place for the development of the site has been successful, but further monitoring will be undertaken in 2018 in order to establish the number and species of bats using the site.

St Tewdrics

The site at St Tewdrics consists of an old 19th century Italian renaissance style villa which is now a wedding venue and can be rented out by couples and their families. The ownership of the building belongs to the Welsh professional racing cyclist Geraint Thomas and his wife Sara, who were the first to get married at St Tewdrics in 2015. Their story can be read here.

From the first wedding vows undertaken at St Tewdrics in 2015, the idea was born to enable couples to spend an unforgettable time at the place, where people can feel a homeliness to it and a relaxing private atmosphere.

An old barn behind the main building was converted into a wedding hall and connected to the villa by building a roof over the courtyard. Planning permission was sought from Monmouthshire County Council, who requested that a bat survey should be undertaken on the barn before works could begin.

Surveying for Bats at St Tewdrics

The initial inspection for bats was done in June 2015 and following three further flight surveys we confirmed that the site was used by common pipistrelles (Pipistrellus pipistrellus), soprano pipistrelles (Pipistrellus pygmaeus), brown long-eared bats (Plecotus auritus) and lesser horseshoe bats (Rhinolophus hipposideros). Lesser horseshoe droppings were recorded inside the first floor of the barn, and during following flight surveys it was identified that the building was used by a maximum of five lesser horseshoe bats, seven common pipistrelles, one soprano pipistrelle and one brown long-eared bat. Mitigation was designed according to each species’ requirements and has been successfully implemented.

Mitigation for Bats

External View of Bat Access into Bat Loft
External View of Bat Access into Bat Loft

A bat loft was constructed measuring 5m in width, 2.6m in length, and between 1.3m to 3m in height. The loft was lined with 1F bitumen felt, and additional plywood plates were attached onto the timber rafters in order to create different types of bat crevices. The bitumen felt was left torn in several places in order for some species of bats to be able to crawl through it. Five raised ridge tiles were also incorporated all along the roof, as well as gaps leading into the soffit box which was positioned on the gable end on the site of the bat loft. A broken window along the north-eastern elevation was originally used by lesser horseshoe bats to enter the first floor of the building and consequently the same access point was also retained for lesser horseshoe bats later on after the bat loft was constructed. The broken glass was removed, but the topmost window compartments were left open for the bats to be able to pass through.

Stone Arches at Rear of Barn
Stone Arches at Rear of Barn

During one of the dusk emergence surveys, it was noticed that the horseshoe bats utilised a stone arch at the rear of the barn as a ‘light-sampling’ area.This behaviour has an important social function prior to the bats leaving the roost.

The stone arch had collapsed under the weight of the scaffolding and was later rebuilt with an additional arch added next to it. The horseshoe bats now have two chambers which they can use before flying off to their foraging grounds. The stone wall of the arches has several gaps where mortar has been deliberately left out which can be utilised by crevice-dwelling bats.

In addition, several gaps were left without being fully re-pointed at the back wall of the barn for the crevice-dwelling bats to be able to roost within them. Several gaps were unintentionally left without being re-pointed in the wall surrounding the barn and therefore numerous gaps remain available for use by bats.

The brown long-eared bat found roosting in the barn will be able to utilise the pupose-built bat loft (together with lesser horseshoe bats) as well as crawl into the space between the roof lining and the roof tiles all along the length of the barn roof. Two Schwegler bat boxes were also installed on an adjacent tree before renovation works began and will be left on site permanently for any bats wanting to roost inside it.

A special lighting plan was also designed in order to keep the illumination of the wedding venue as low as possible, especially along the northern elevation of the barn. A laurel hedge was planted in order to screen the path, leading to the bat access into the bat loft along the north-eastern elevation. The main entrance into the wedding hall is through the corridor connecting the villa with the newly converted barn. The space designated for the outside gathering of the guests is along the south-western elevation, away from the bat loft and the stone arches utilised by lesser horseshoes to minimise any disturbance.

Bat Droppings found in New Bat Loft
Bat Droppings found in New Bat Loft
Internal View of Bat Loft
Internal View of Bat Loft

 Monitoring the Wedding Venue for Bats

The internal inspection of the completed bat loft showed positive results! Further monitoring this year will show if the external lighting needs to be adapted and the exact number of bats currently using the building, as well as which species they are and their new flight paths. The builders on site were very conscious of the bat mitigation needed to be implemented and this can be seen from the photographs provided. St Tewdrics is an example of a project where ecologists, building contractors and the client, if working closely together, can achieve positive results, despite the difficult circumstances of having to satisfy roosting requirements for a vulnerable species, such as the lesser horseshoe bat.

The guests at the wedding venue, if interested and naturally curious, will be able to observe these fairly unknown creatures as they utilise the northern and eastern elevations of the building, while the guests party along its southern and western sides.

Please follow our website for an update of the monitoring results and the final outcome of this project.

Our guide to bat mitigation can be found here. For more articles on the mitigation that we have conducted, please see the following link: Bat mitigation Forest of Dean.

For more information about bat surveys, please see the following links:

Bat Survey Information   I Need a Bat Survey