The build was originally begun October 22, 2018 and as of today is still ongoing.
I've copied some parts directly over, added some new info and pictures,
and modified some parts of copied posts for a clearer explanation.
I'll update things here as the build progresses.
I thought it might be of interest to a wider range of readers in this forum.
About 10 years ago I bought a Thomas Yorke roundhouse kit on eBay.
I had every intention of building it by the instructions but several things interfered.
Probably the biggest was that we sold almost everything we owned and moved onto our boat.
I did have one day of sanity and put all my train stuff in storage.
The other thing that held me up was painting the plaster walls.
I had never done it before, painted plaster, and couldn't find a technique that really met what I wanted.
I did get as far in the build as finishing the interior framework before packing it away for ten years.
This overhead view shows the interior a little better. I was originally planning to have four full-length inspection pits with one of them being set up for removing driver wheels. I think this time around I'll shorten up the pits. I still plan to have one pit for removing driver wheels but I've recently seen a prototype driver pit and have a better understanding of how that whole operation works. I'll try to include that detail.
Now ten years later I'm back on dry land and starting a new layout. I did the track design using the AnyRail program. I included the roundhouse but I've recently gotten involved with building from scratch and wanted to modify the kit. I'd like to add a machine shop off one side and add skylights across the roofs of both buildings. The skylights will require modifying the walls that came with the kit. I went back to AnyRail to see what I could fit in my limited space. My latest plan was to have the machine shop share space with a car shop and have the track lead in from near the ash pit. Since doing the design below I've decided the machine shop was too confined. I redirected the track down the side of the shop where a wood platform will serve as the car shop and the machine shop will have the entire interior space. There will still be a section of track leading through the right hand door of the shop which will be used for wheel maintenance and repairs. When I get a chance I'll post an updated track plan.
I chose to start with the machine shop since it has a shared wall with the roundhouse. I wanted to build the shop with the same architecture as if it was built at the same time as the roundhouse. The roundhouse walls are stone with large arched windows and buttresses supporting the midpoints and ends of the walls. It would save me a lot of trouble if I could make molds of the roundhouse walls and cast copies for the shop. The only hitch would be that the kit walls are 17" long with four windows and the shop will only be 12" with three windows. That will require some cutting and splicing. The roundhouse walls also taper down from front to back and the shop walls will be straight. I began the process with full size drawings. Below is the side wall for the shop.
I made latex molds of the walls and built wood frames to support them. The support was needed to get the walls to come out straight and flat. I hadn't done any plaster work in years so this was all a learning process. I made the walls the way I used to make rock molds for scenery by coating the surface with three layers of liquid latex, then two more latex layers with gauze to add strength to the mold, and then finally three more layers of latex over that. Eight layers all together. I'm sure manufacturers have a better technique for this but I don't know what it is. Pouring the plaster was also a learning process because small bubbles formed on all the edges of the details ruining the casting. I found that pouring a half layer of plaster and then tapping the bottom of the wood frame with a hammer would remove most of the bubbles. Then I would pour the rest of the plaster before anything started to harden. I ended up with about five failed attempts before finally getting the right technique down but those failures came in handy later on when I was practicing painting the walls.
To make the side walls for the shop I needed three two window castings. I cut the buttresses off each end and removed the stone cap from the top, making the top level instead of tapered. To mate the third window to each wall I made 45 degree angle cuts and smoothed each piece with a wood file until they mated perfectly. I used wood glue to hold the pieces together. To finish the joint I carved the plaster with a dental pick to mate the adjoining stones. I found that the wood glue was a really good choice when I dropped one of the completed walls and it broke in a different spot than the glued joint. That was pretty impressive.
The shop has a skylight doghouse along the full length of the roof which will continue across the roundhouse roof. This required the end walls of the shop to be made from scratch. I thought about making them from wood but finally bit the bullet and made my own plaster castings and carved the stone details to match the rest of the walls. Below is the drawing I worked from for the end walls. The inspiration for the shape of the walls came from some old photos I found on the net of shop buildings at various railroads. Most of them were brick but I liked the arched entrances and the roof shape with the skylights.
My original plan was to combine the machine shop with a car shop so the large arched door on the right was intended for the car shop. After I finished all four walls I realized the machine shop needed more floor space so I moved the car shop outside. I didn't want to redo the end walls so I justified the arched doorways by saying this was the original engine house and the roundhouse was added afterwards. My railroad doesn't have a prototype so I get to make up the history to suit my needs. Carving the stone was done over several evenings. I would draw out the stonework on a small section of the plaster with a pencil and then carve it with the dental pick. In the photo below you can see the next section to be worked on to the left of the round window has already been penciled in and is ready to begin carving.
The next step was to paint the walls so I spent a lot of time hunting for a good technique to give me the look I wanted. I found what I wanted here (https://www.nebrownstone.com/blog/painting-new-england-brownstone-castings/) but instead of following their instruction exactly I modified them for the look I was after. I spent the afternoon developing my technique. I had a pile of reject wall castings from when I was learning how to pour plaster that served well as practice platforms. In the picture below the wall on the left has about five different techniques. I'm going with the technique used on the wall on the right. It uses five different acrylic tints with an India ink wash along the grout lines. The plaster casting was first sealed with a flat clear coat of spray paint. Then I used a chunk of natural sponge to blob on grey, Mississippi mud, burnt umber and burnt sienna followed by a selective wash of raw sienna. I also painted individual random stones with burnt umber to make them stand out. When dabbing on the colors I started with the lightest color and added successive colors to that instead of using individual colors. I think in the end this is what gave the stone the multi-colored look after it was polished. Then I flowed in the India ink on the grout lines and dabbed off excess ink from the tops of the stones. Goes pretty fast considering I waited ten years to try this.
I was going to stay with the dark grout lines but it just didn't look right to me. I tried smearing artists gesso into the grout lines of my practice pieces but that just made a mess. I then tried joint compound for plasterboard. I smeared it over the entire wall and then cleaned the surface with a clean wet sponge. The result was exactly what I wanted. Even better than I had hoped for because the joint compound filled the grout lines but also worked with the paint. When I wiped the surface clean I think it polished it and brought out the color.