The original walls of the bus are an interesting space because they are recessed by the floor and then jut out about a foot off the floor, making the wall as a whole uneven. This has created some challenges for us in customizing our build as most things need to be flush with the wall and the floor to be secured. We also had to make decisions about how many windows and which windows we wanted to board up. Boarding up select windows has been a very important step in making the space feel more private and homey.
In this post: Lower Walls Boarding Up Windows
Lower Walls
After tearing off the aluminum sheets of the original bus walls and removing the old, damp batting insulation in them, we were left with open cavities. The plan for these lower walls was pretty basic: fix any leaks, replace the old insulation with new insulation, and enclose it all with a thin layer of something other than 10 year old aluminum.
We started by framing out the walls with 3/4 inch furrings. We wanted the furrings to be substantial enough because these wood panels and our floor is what everything we build will be secured to.
The cavities of the wall are only accessible from the opening about a foot above the floor but they do extend down to the floor. This was an awkwardly narrow open space that was hard to see and work with. The rivets from the outside of the bus protrude through the wall and stick out in this cavity, so trying to push batting down into the enclosed space would have been difficult. Our solution was to fill it Great Stuff Spray Foam Insulation, which was easy and worked great.
Tip: Great Stuff comes out small but quickly expands and then hardens into a bulbous shape. It comes with a straw for easy application into small spaces. Once you start a can, the straw will only be good for the one time use as the insulation in it will harden.
To fill in the rest of the cavity, we decided to use Safe’n’Sound Rockwool Batt Insulation, which claims to be made of natural and recycled materials and is safer to handle as it does not have any fiberglass in it. However, this insulation should still be handled with gloves as it can cause skin irritation. The insulation was easily cut using a knife.
We chose 1/8 inch hardboard to cover the lower insulated walls. This came in 4×8 foot sheets so we cut what we needed with a circular saw and secured it to the wall furrings using screws and liquid nails.
Due to water leaks, our hardboard unfortunately developed large water marks in a few places on the passenger side. We primed and painted the hardboard white to freshen it up.
Boarding Up Windows
Our 5 window short bus has a total of 13 windows in the body of the bus (5 windows on each side and 3 on the back wall). We chose to board up the two small side windows on the back wall and the last three windows on the driver’s side. Roughly two of the windows we boarded up would end up in the bed space and the third would be storage space.
We used 3/4 inch tongue and groove pine boards and painted one side black to black out the windows. We double checked where the stock wires for the bus ran before drilling. Some wires go down the metal frames between the windows and we didn’t want to install any screws where they might hit wires. This was mostly an issue on the back wall because we could see that wires were tucked into the back left and right corners of the bus. To avoid drilling into them, we used metal “L” brackets and screwed the boards into the adjacent side wall.
We drilled normal screws on the other end of the board because we don’t see any wires going down the emergency exit door frame. We predrilled each hole and countersunk the screw heads.
Tip: Pre-drilling holes refers to the process of using a drill bit to make a hole in the materials you intend to screw together so that when you drill the screw in, it already has an easy path to follow. When pre-drilling, you want to use a drill bit that is similar in size to the shaft of the screws that you intend to use NOT INCLUDING the threads of the screw that will "bite down" into the wood or metal. If the drill bit is too big, the screws won't "bite" into the material and they'll be loose. Countersinking refers to the process of using a drill bit to make a shallow hole for the head of a screw so that it can lay flush with the board. This prevents screw heads from sticking out further than the board and in some applications, from getting in the way of the next steps of the project. In this case, you should choose a drill bit that is the size of the screw head. To countersink into thin or soft woods, we put the drill in reverse and push the bit spinning backwards into the board. This prevents the larger drill bits from catching on the wood and going too deep. When dealing with thick or hard woods, we suggest approaching the board with a high drill speed and only pushing very gently. This will encourage clean drilling while also preventing the drill from catching on the board and going too far.
Next, we moved onto boarding up the 3 side windows. We wanted the boards to lay flat on the window frames but the screws and washers on the window frames pushed the boards out significantly. Travis used a router to make circular indents in our boards for the screws to fit into.
Tip: A router is a power tool with specially shaped bits that are used to make grooves and indents. This tool is mainly used in woodworking and cabinetry but can also be used on plastic.
The final touches included cutting the front ends of the long boards at a 45 degree angle and hiding the screw heads with wooden screw hole plugs. We later finished the pine boards with danish oil to seal and protect the wood. Of course if we did this again, we would oil the boards before installing them to make sure we got every nook and cranny of the tongue and groove.
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Great Stuff Foam Insulation Rockwool Batt Insulation Router Wooden Screw Hole Plugs Danish Oil