going to put it in attic
NOT a good idea! There are lots of threads scattered around all the various forums about where to build a layout.
Attics, unless fitted with proper floors, insulation, access stairs, and electricity, light, and ventilation, are more trouble than you would believe.
Taken to an extreme example - power from an extension cable plugged in to a socket in a bedroom, access via a chair balanced on a table on the edge of the stairway, you have arthritis in a hip, there is no proper floor in the attic, and there's a power failure while you are up there, at ten pm! Now - get out without putting a foot through the ceiling, or falling out of the hatch and down the stairs!
Being sensible, in summer you will roast, in winter you will freeze. Boards will buckle from the damp. All your models will get filthy, and so will you!
Before you build anything in the attic, you need to do a lot of forward planning, taking into consideration access, safety, and the house structure. You will be amazed just how heavy a solidly built railway layout is, and unless the attic floor has been reinforced, it will not take the stress.