Oak House, Derbyshire

Original Building
1. Location

Geographical region: 
East Midlands
Town: 
Nether Biggin
Name of council or planning authority : 
Peak District National Park
Name of consultant: 
Turnstone Ecology
Name of architect: 
John Williams
3. Details of proposed work and associated impacts

Type of impact to bats or roost: 
Roost loss
4. Description of roost (before mitigation)

Bat species found on site: 
Brandt's bat - (M. brandti)
Common pipistrelle - (Pipistrellus pipistrellus)
Age (estimate of how long the roost has been in use): 
10 yrs +
Size (estimate of number of individuals using the roost): 
Approx 10-12 Brandt's and 5 Common Pipistrelles at the time of survey
Use Type of roosts (e.g. hibernation, spring gathering, maternity, nursery, swarming): 
maternity
day roost
Location in building: 
In loft, below ridge tiles and between roof tiles and lining
Aspect (direction facing): 
Parts of the roof being used by bats faced south east, south west, north east and to a lesser degree north east
Description of immediate emergence environment in relation to the roost: 
Brandt's bats were emerging from a hipped ridge on the W aspect of the building and flying to nearby woodland
Roost substrate (e.g. brick, stone, wood, roofing felt): 
At wooden ridge, and between concrete tiles and roofing felt
Evidence of insulation?: 
yes
(If yes), name/brand: 
Fiberglass rolled insulation, brand unknown
Height of roost above ground: 
4-5 m
Roof covering: 
Concrete tiles
Lighting levels inside roost (lux reading) - Day: 
Very dark! i.e no obvious gaps at eaves
5. Description of access (before mitigation)

Size of access: 
Brandt's bats were accessing via lifted tiles which were lifted by between 15 and 20 mm. Common Pipistrelles were using lifted lead flashing which was lifted by approximately 20 mm
Location in building: 
Brandt's were predominantly using a row of lifted tiles along a west facing hipped ridge. Common Pipistrelles were using lead flashing on the eastern aspect of the building
Height of access points above ground: 
4-5 m
Aspect (direction facing): 
West and south east
6. Description of mitigation

Type of mitigation and compensation: 
Purpose built roosts (e.g. bat boxes and bat barns)
Objective of mitigation: 
To move the maternity colony of Brandt's bats and day roost of Common Pipistrelles to a purpose built bat barn in a separate area of the clients land so that populations of bats could continue to use the site and so that the local and regional populations of bats were not adversely affected
Method to achieve objective: 
The replacement barn was constructed over winter 2012/13 and was built using as much material from the old roost as was possible without destroying the roost. This involved using wooden weatherboarding from the front of the original house, and removing the insulation from the original house and filling the new barn. The replacement barn was designed to replicate the locations bats were observed using, including; ridge tile access, raised tiles along the hipped end of the barn, lifted lead access tiles and internal beams. The aspects of each face of the barn were positioned so that the solar regime the new building was subjected to would replicate that of the original structure. Once the barn was completed and the weather was suitable the roof and ridge tiles were stripped by hand and the bitumastic lining was also removed (all tile stripping was completed by our intrepid licence holder Simon Parker who was roped to the roof)
How is success of mitigation to be measured: 
Use of the replacement barn by individual Brandt's and Common Pipistrelles and in time the presence of breeding bats at the site.
Location: 
Approx 60 m north of the original building
Size: 
The overall dimensions of the building are 5 m x 7.5 m with a ridge height of approximately 4.25 m. The internal ridge height of the bat loft area is 2 m
Materials: 
Oak main frame, softwood pressure treated internal trusses, a mixture of new and reclaimed concrete roof tiles, bitumastic lining, reclaimed wooden weatherboards from original house, lead flashing and plyboard flooring
Additional info: 
The planned location for the replacement bat barn contained several small trees and was adjacent to an outgrown laid hedgerow. The small trees were removed or coppiced and the hedgerow was re-laid so that the amount of sunlight hitting the new barn was as high as possible
Estimated cost of mitigation construction (optional): 
Approximately £20k
7. Monitoring Data

Average daily temperature: 
Unknown at time of 1st monitoring as data logger failed but the internal temperature was 7*c higher internally than externally at the time of the first monitoring visit (29.5*c inside, 22.5*c outside)
When this temperature data was measured: 
2013
Evidence of bat use post mitigation: 
The internal walkway and beams were swept clear of bat droppings following the installation of the old insulation to allow easier identification of fresh bat droppings. Common Pipistrelle droppings were found scattered over this and a small collection of Brandt's droppings were found in one location. An emergence survey was completed in July 2013, during this at least two Brandt's bats emerged from the new bat barn (one from the south west hipped end and one from the west side of the ridge) along with an individual Common Pipistrelle which emerged from the western face of the roof
How long did it take for bats/signs of bats to appear?: 
Pipistrelle droppings were found within 4 weeks of completion of the bat barn (April 2013), Brandt's bat droppings were found on our monitoring visit which was completed in July (4 months)
8. Measures of success
Based on the objective of the mitigation do you deem the mitigation to have been successful?: 
Yes
What alterations could be made to make the mitigation more successful?: 
Possibly add more insulation at a later date, and if temperatures are not shown to be staying high enough heating will be added in an attempt to encourage bats to breed on site once again.
Are there lessons from this project that you would like to highlight?: 
Little is known about Brandt's bats and their requirements with regards to mitigation and roost specification. This project has given an indication that replicating as many features as possible between the original roost and the replacement roost is important. This along with another project involving Brandt's roosts we have had over the last year has led to the suggestion that this species of bat is sensitive to temperature changes within a roost. Both the roosts were inhabited by people until approximately two years ago, and the evidence we found within would suggest that the roosts were previously much much larger (Oak House contained huge numbers of droppings under the ridge tiles, below lifted tiles and within the loft space - many more than the numbers of bats we found during surveys could produce even over a long time period) We were very lucky to have a willing client, an experienced architect and an excellent builder, all of whom listened to our instructions and implemented them as required.
9. Photos (before and after)

Before – outside showing roost location: 
Before, Outside showing roost location - Roost 15/08/2013 - 12:17pm
Before – inside of roost: 
Before, Inside of roost  - Roost 15/08/2013 - 12:01pm
After – outside showing mitigation: 
After, Outside showing roost location - Roost 15/08/2013 - 12:09pm
After – inside showing mitigation: 
Before, Indise of roost - Roost 15/08/2013 - 12:09pm