Check the fuse if okay Disconnect battery for 10 mins then reconnect my caddy does it when there frozen you might get a steering wheel symbol pop up but that will reset it's self
If you're joining the joists on the load bearing wall should be okay but if you're doing lengths the full span you would only get them in by removing tile and sliding in from a scaffold
I've got a couple of Spyder waterproof hoodies for when not too cold and gortex army jackets when wet an cold you can get them pretty cheap from surplus stores