Hi, I don't have any experience of building layouts in an attic, but as regards the surface on which you will be laying your track, I would definitely, definitely get it as smooth as possible. Time and effort spent here will be repaid with reliable running for as long as your layout is in existence. Just think how annoying it would be if you laid your track and completed your scenery, only for trains to keep derailing, thus leading to you having to virtually dismantle the whole thing, in order to smooth out the track base.

As regards rails expanding in the heat, one way is to lay the track on a hot day, thus ensuring that the rails have expanded as much as they are likely to. This may not be practical, though, unless you are happy to wait around 6 months! Also, if you do that, the subsequent contraction in colder weather may open up gaps that in themselves cause derailments. May be better to lay the track in an 'average' loft temperature, but leave small gaps in the fishplates to allow for expansion. Also, probably better to fix the track down as securely as you can, ideally gluing it with something like PVA.

Perhaps you could put a photo or two up in this blog or a fresh blog entry, so that we know what we're looking at?

A bit of sanding might be sufficient, but it really depends on what the surface of the baseboards is like, plus the joints between the boards.

I've been in my present loft for years, but until I had a conversion, expensive but well worth while, it was grief! It ain't just heat, there's cold as well. I made it that summer peak to winter low, there was about 40degree difference, so you must allow for expansion/contraction, unsoldered track joiners with flexible jumpers in particular. You also get dew forming in the cold, so oxidation/rust can happen. There's a window for reasonable working conditions for some weeks April and September, rest of time iffy for comfort. Your photos show you're trying some insulation which might help, but you need to bear in mind roof spaces need ventilation to preserve the structure, which conflicts with your comfort, and you really need good expert building advice if you start trying improvements. Sorry to sound a wet blanket, I'd like to see you succeed and enjoy your modelling. There's a good site, worth reading up on here, by Mallard60022, 'In the spirit of Seaton Junction' which gives a good idea of modelling in a loft. Anyway, all the best with your project.

I hope I haven't been too much a prophet of doom, certainly I don't want to put you off a great hobby. If it is all completely new to you, maybe a small line to gain experience, build up stocks, and get expertise, would be good sense, as you propose, rather than being too ambitious with a big oval at your first attempt. In the meantime, you can get an electronic thermometer with max and min recording, and see just what does happen up there. Also in the meantime, have a good luck round this website, and see what people are getting up to, there's immense variety, and you'll find something I'm sure you'll identify with.

Keep this post going. We'd like to know how you get on. Good luck.

Get the missus onside and you'll have a good railway, class 40, she's a treasure!