I plan to put a 130’ turntable and Walters 3 stall roundhouse and a 2 stall engine shop, and maybe two tracks in between the two buildings, along with a return loop going around the back side of the buildings. All this will be going in the corner of the two joining walls.How much space would I need in feet to pull this off. I am modeling in HO. Thanks for any advice. need all the help I can get Thanks again Sam
Not sure of your space requirements, but what I did was make a cardboard template of my turntable and one of the measurements given for the roundhouse. May have to change plan, so not sure if I will use it or not. However, make templates of all the buildings you want to use, one for the tracks between the buildings and go from there. Your return loop will have to be large enough radius to go around the whole thing, at a guess it will not be too tight for long engines, but keep it in mind.
Will the engine shop come off the turntable?
You say you want to back this into a corner. How will you access the tracks in the back? A turntable and roundhouse take up quite a bit of space. My thought would be to cut out the corner of your layout surface and curve a backdrop in front of your access hole, but have it short enough to reach over to get to the derailments that will surely occur if you do not have access.
Good luck,
I have my engine servicing facility on a 36" x 96" section, I have a full facility with a lot of lead in tracks, coaling tower,ash-pit, etc.the hole nine yard with no loop running behind the round house as thats where I have plans for the back-shops and a transfer table in your case it’s all predicate don how big of a loop do you want to make the track behind the round house I would say no less the 24" radius allowing for ample clearance between track and structures maybe a tad tighter but you have to consider what size engines are you going to be running/ Looking at mine a 18" radius curve would just clear but be tight for any large sized locomotive providing that is you don’t put any buildings like the machine shop etc. next to the round house.
I have a Walthers 130 ft turntable and roundhouse kit.(not installed on layout yet)
My layout now is 6 feet wide by 24 feet long( totally walkaround) and the TT and roundhouse will take up so much room , that the only way I see to use the turntable is to add another table.
If I use it on the present setup (which is not finished) I will have to make serious changes.
The 130ft TT and roundhouse takes up a lot of room.
The reason I went with the 130 ft TT is that I have several really long steam engines, several 2-8-8-2’s and few other long steam engines , but using it on my present setup I am building , I would have to rethink some of my other layout designs.
I am trying to build my present layout so I can run 4 trains simulataneously, but the big 130 ft TT wouldn’t allow for that.
I may end up not using it and selling it, but not sure yet
Unless someone out there can show me how I can make it fit?
I’m open to ideas.
TheK4Kid
This is what I did. The basic table is 4 1/2 X 8 1/2. I wanted a loop around the scene and a small yard leading to it. You can see the yard is not yet laid. Maybe this will help you decide how much you need for what you want. 
Draw it to scale on paper or CAD. You can get the dimensions from Walthers. Don’t rely on guessing or eyeballing pictures (although they can help).
Dante
Hello, ART. That looks really good to me. I was planing on setting the RH & T-T and the engine shop all in the corner of the room, but I like what you have there, so I am thinking of maybe adding a peninsula. On the end of the peninsula should be at least 4 1/2 x 4 1/2 '. Do you think that will work? Thanks, Sam