Here are some of the incredible ways to use old doors to create great spaces with nearly no carpentry work. This is a way to have raised panel wainscot, a beautiful bathroom wall, and other ways to make your Tiny Spaces unique, but they can be used on big spaces too.
The big secret to this is to lay the doors out before you lay out the electric outlets so that you do not have one come out on the edge of a panel or rail and not have the cover fit on properly. Here is also an example of how that layout goes.
You will find some great old wood in the doors that were built prior to 1900. Often, up North, you will find exotic or expensive woods that were once common, now hard to find and expensive, but in the form of an old door, they are cheap. Black Walnut, Butternut, Cypress, Hickory, Long Leaf Pine, and other great types of wood that were stable and strong were used to make doors that you can often buy for less than the wood costs new at a specialty wood store as these types of wood are not found at the big box store.
Off from a demolition site, a salvage job, or out of an architectural antiques store, you may be able to find them at a price that you can not pass up compared to the alternatives available today, like plywood, particle board, and other outgassing new building materials. The antique doors are all cured, often only covered with varnish that can be removed by washing them with simple cheap ammonia cleaner, ammonium Hydroxide being the key ingredient at full strength, and the varnish melts away. Ideally, Milk Paint is a great pre-existing finish, but you can also strip lead based paints off with a bit of care and they work great or leave the paint on and add a coating to encapsulate it so that it will not be dusting, or exposed later.
Installing a door to be a wall is as simple as putting down a 1/2″ strip of wood on the floor and butting the bottom of the door against it, and if possible, the top would go straight up to a loft beam that the top can be screwed to. It will add strength to the beam so that you might get by with a smaller loft beam as well as stiffen the wall. By putting one big pocket door as I have, as much as 5′-6′ in a single door, you then have a great wall. I have set several doors side by side to form the wall before and then put a knob and faceplate over the holes in the door for decoration. NO reason to hide what was done as it becomes a great conversation piece for guests.
I have also used two doors for the bottom of the Murphy Beds we make. If you are using a strong wood like Long Leaf Pine, the doors will give you all the support you need for the bottom of the bed structure. There are a number of ways of hinging it, counterweighting it, and even adding a block and tackle or pulley if you do not want to build a counterweight system. The weight of the mattress will determine what you will need to raise and lower it other than a really strong back.
Wide pocket doors can also work as a bottom for a Twin sized Murphy Bed as there are doors at 40″ wide and that can then be mounted on the wall so as to lower down sideways or longways to reveal a futon mattress and only take up a few inches of wall when put away. While I have not yet done it, we may well still use some of the thousands of paneled doors we have in stock to cover an entire ceiling. This would be a cool way to give depth to the room without a lot of extra work since there are not outlets and other things to get in the way on the ceiling like there are on the walls.
I hope that gives you a couple of good pointers to keep more doors alive and thriving for another hundred years in tiny houses. For quick closets in a house, for tables, work benches, and many other things you can create that I have not covered here, please check back and let me know if you liked this one and I will do another.