Brief summary of Part 1: the bat man checked for bats and found bat poo indicative of one bat, but couldn't rule out the possibility of there being more bats hidden between the felt and the tiles of the roof. He then wrote us a bat plan which received the necessary approval from the bat people at Dorset County Council, once we'd resolved a few glitches (they initially failed to read the plans properly).
The bat plan (Dorset Bat Mitigation Plan/DBMP) sets out an approach to roof works that will minimise any potential disruption to bats. Although the plan describes "a bat roost of low conservation significance", we have to act as though there may be
more bats roosting in the space between the roofing felt and the
concrete roof-tiles, just in case. Had we known earlier about the need for a Bat
Survey we could have carried out emergence surveys - checking at dusk to
see how many bats emerge from the roof - and based the Bat Plan on more
specific information. Sadly, it was already October by the time we
knew a survey was needed and at this time of year the bats aren't
active in that way. I'm not sure what they are doing, but it isn't flying in and out of roof roosts.
The primary restriction that the discovery of bats imposes on us is that work affecting their roost must be carried out either in March/April or October/November; when bats are neither hibernating nor breeding. Strawbale building is primarily a summer activity, in order to keep the bales as dry as possible and to allow the breathable lime-render to be applied and cured before any chance of frost. The roof work needs to be done first, so that extensions to the roof are in place to cover the new bale walls that will wrap the existing bungalow. That leaves us now aiming for the March/April window of bat-safe roof work.
It should be possible to complete the majority of the roof work in two months, even if we find all the battens are rotten and need to be replaced. It will be quite tight to get it all done, but possible. Within that time we also have to make alterations which will bring the ceiling of the living room/kitchen area up to roof height. The DBMP requires us to have completed this and to at least have boarded the remaining loft area off by the end of April so the bats have somewhere dark to come back to.
My main concern about the deadline is not finishing the roof work in two months, but whether or not we can be ready to start it in time. We haven't even submitted our planning application yet. Even if we are lucky and do get permission first time (which is not definite by any means, although we have tried to do everything we can towards that happening) it can take 8 weeks to get a decision, presumably longer if it stretches over the Christmas Period which our application no inevitably will do. If we get planning permission, we will then need to obtain advice and construction design info in consultation with a structural engineer and building control to ensure that the changes to the roof structure will be safe and comply with regulations. We'll also need to source and order all relevant materials and book scaffolding etcetera. Some of this can be done concurrently (materials research especially is something I've spent a lot of time on already, for the project in general). But the fact that we now have 3 and half months to get all of this in place if we are to even begin out project next year is terrifying!
The other requirements of the Dorset Bat Mitigation Plan/DBMP are less stress-inducing. We need to install two bat-slates in the ridge of roof. These are bits of lead (or other) flashing which follow the contour of the tile below them but leaving a gap for bats to enter the loft. Inside the loft we will fit a couple of crevice roosts: two rough surfaced boards (rough so that the bats can get a grip on them) held 20-25mm apart to create a space for bats to sidle into and sleep.