At this point in the process, like a lot of the steps along the way, it will be entirely up to you what kind of work you want to put in.
Ceiling: This is another subject of much discussion among bus builders. Whether or not to remove the inner liner. There are some reasons why you should and reasons why not. I’ll start with the pros: First is to be sure there isn’t any water damage or leaks that need to be addressed. Without removing them, it is very difficult to see where water can be leaking in. When you are spending a lot of time and cash on a project like this, you don’t want it ruined by a faulty roof. Another reason is the possibility of rodents making nests and leaving traces of nastiness in the insulation. Which leads me to IF you have proper insulation, or any at all for that matter. A bus is a giant metal can that doesn’t do well in extreme temperatures without help. If you find you have no insulation, then I absolutely suggest you get it taken care of. The last couple of reasons for removing the ceiling would be to create mounting points for a roof rack, for framing, or whatever else you need to support. And then there is the ability to remove old wiring, and add new.
Cons: It’s difficult to actually call these cons because it’s also a great option to not remove it. I will say that it is a lot more work to remove them! Most of the time, simply painting the existing metal ceiling is a quick way to create a beautiful space! You can leave the bare metal and simply screw wood planks, or any other material you choose. You also won’t have to deal with all of the following steps:
Removal. You will find that some bus headliners are attached with screws and others with rivets. My GMC was fastened with rivets and it was a nightmare. I have heard from other owners that have screws that say the same. Screws will tend to rust and strip out, causing you to drill them or cut them off. With rivets, you will always have a big work load ahead of you. First, decide which direction the metal is overlapping and remove from the top layer. There are a few solutions to remove rivets, and will gladly accept more options if you have them. One way is to pop them with a heavy hammer and a punch. It takes some major force, but a lot of people swear by this as the best solution. In my case, I used an angle grinder with a cutting tip to ‘X’ the rivets before I chiseled them off. ABSOLUTELY TEDIOUS WORK. Drilling them is also one of the best ways to remove them. Probably what I should have done, but went the hard route for some reason. The use of pneumatic air tools could have also been of great benefit here. Wear your gloves, mask, and safety glasses as always!
If you have taken the time to fully gut your rig anyway, reseal your windows! On school buses, windows are the number one spot for water and air leaks. On most models I have seen, removal is the same. There will be 4 screws with large washers holding them in place, as well as some form of sealant. After removing the screws, all I needed to do to pop them out was to slice along the caulking with a razor, gently insert a flat pry bar or screwdriver between, and push them inwards. The ease in which mine came out both surprised me and helped me realize how much the needed to be resealed. After removal, scrape all of the old gunk off of the windows and the seals. Use an outdoor window and door sealant around the edges, making sure to get all points of contact. Push the window back in and reattach the screws. Afterwards, I also did a bead of caulking around the edges to further seal from water.
Removal and covering of windows: I chose to remove 3 windows from both sides of the bus for my closets and bathroom. I simply framed the old metal frame with wood, making sure to also use construction adhesive and predrill my holes. I then used the metal from my old ceiling as my new outer shell. Owning a sheet metal shop comes in handy here as I was able to make perfectly straight cuts. You can hire an HVAC professional to cut them for you, or use hand tools. Again, seal them with watertight caulking and then screw them to the wood. Caulk the edges once again to prevent any leakage. Be sure to prime any metal that isn’t already painted to prevent rust damage.