I was lucky with collecting pallets for my bar project. I emailed a local company to me as noticed they had a huge pile of pallets and asked if I could have some and luckily they said yes.
I probably collected about 140 pallets over the course of a couple of months. I decided to go big as have plenty of room in our garden. I made the base 7 meters long by 3 meters wide so I could use the whole pallets to fit up to the edge as they are a meter wide.
I cut small pieces of wood to screw each pallet together for stability and also used long screws to go through the wooden blocks on the pallets. Once the sides were complete, we used 4x2 pieces of wood for the roof beams, then used OSB board for the roofing plus four rolls of felt. That and the concrete base were the most expensive part. The windows were from a house that was being refurbished and was free. The doors were cheap from eBay.
We used the pallet slats to clad the outside over a waterproof membrane. I bought a cheap reciprocating saw to take the pallets apart, which was a bit time consuming but worth it. I also clad the inside with the slats but also used some plasterboard as to break it up a bit as didn't want it to look like a sauna.
I made the bar inside from reclaimed glass bricks and pallet wood. The floor is also free wood which is another type of stackable pallet again from a local company. The floor and bar are varnished with a floor varnish called No Nonsense, and it is fantastic varnish and looks brilliant considering it was only £10 a tin! We loved building this. There are bits I would do differently if I did it again, but having said that the result is awesome, and those that have popped round for a beer have loved it too!