Polystyrene..?

[mick]

One of the things I've been looking into recently is insulation sheets for lining the interior of the shed to help stabilise internal temperature. It's got me wondering about the properties of polystyrene sheeting - the type used in the construction industry as wall/floor insulation and whether it would be possible to use it as a successful track base outdoors. Is polystyrene weatherproof? Can it be used outdoors?

A portion of my intended new layout will be at or very close to ground level and I'm concerned that any timber used in such close proximity to the ground would quickly succumb to the levels of damp and moisture found in that situation. Polystyrene appears to be pretty resilient when left outdoors. Does anyone have any ideas or thoughts on this?

Even if it was deemed suitable there would then be the problem of finding suitable adhesives for use on polystyrene outdoors so this is only a thought that came to mind after seeing the sheeting at my local builders yard. I'm open to any advice.

[IanR]

Not sure about that Mick but what about the recycled plastic base that you mentioned a while ago?

[mick]

IanR said:

...what about the recycled plastic base that you mentioned a while ago?

I'd absolutely forgotten about that Ian Just had to revisit the website to take another look as a reminder. It's definitely what I'm looking to use in the areas that will be very close to the ground although the only curved radius track board they advertise 'off the shelf' is to a radius of 1.125 metres. They do 'curved planks cut to order' which I'm guessing won't be cheap.

[mick]

Polystyrene might not sound like the best material to use in order to construct a solid base for an outdoor model railway but my interest in it is solely as a track base upon which the track can be directly laid. For instance, on the SGR I constructed a building block base upon which I fastened decking boards to take the track. However, no matter how careful you are you're never going to get a completely flat and level base using such timber and if you do, you can be sure that the climatic conditions will soon have an adverse effect upon it. In my opinion, what's required is something that will withstand the weather and remain flat without the warping often associated with some timber products.

I have considered using plywood and feel it is the best option when looking at timber products but even if well protected and sealed, Worsley Dale will require sections of track that are at ground level and susceptible to damp from below as well as the elements from above. If I build a nice solid base, perhaps of masonry construction, do you think that a 25mm thick layer of polystyrene along the tops would be a suitable surface for track laying and would it survive outdoors?

[IanR]

Well I think it would probably be ok to use outdoors, especially if it was treated to a couple of coats of water based masonry paint. Being chewed by wildlife could be a problem. I'm not sure what you would use to fix it to the masonry and fixing track to it could be problematic too as I doubt that it would take pins very well.

[traingeekboy]

i suppose what I see is that the materials being used up till now seem to work. But you may want to explore this new avenue of design.

I'd be curious to know exactly what kind of a thing this is. We use blue and pink styrofoam over here for our layouts. It doesn't have tiny beads like the white stuff and is designed as an insulation. Everyone is pretty crazy about it, but I think it's actually a pain to work with and prefer older methods for building a layout, since everyone covers up the foam with scenics anyway.

One thing I really like about the roofing felt you guys use is that it looks like roadbed already and all you need to do is apply scenics on other parts to make it even more convincing.

[Vagabondic]

With reference to your thoughts on polystyrene as being something suitable for a base at ground level, I have a similar need for a base for a garden railway I would like to construct in the near future - time permitting - and am considering using equine rubber matting - these are 8'x 4' sheets of rubber - normally about an inch thick. We have some for our horses and it is very tough taking everything a big horse can throw at it for years with no obvious deterioration. As it is flexible it would need a firm level base beneath but it can easily be cut to the necessary radius for curves and will easily take tacks or screws so securing track shouldn't be a problem. Does anyone think this would be a good material to use or is there some basic flaw I havn't seen in the plan - other than it being unsightly black rubber

[chris]

My only question would be what about expansion and contraction? Some materials expand far more than you would imagine they would and garden railways can get rather long. A couple of millimetres gap between boards would probably prevent any issues.

[fungus]

I use closed-cell foam as the final track base. It's similar to the material used for camping sleep-mats, and is sold by C&L Finescale (or it might be Exactoscale). I have used several methods of sticking it down. I started by using roofing-felt adhesive. It works well but is messy. I then tried using the roofing-felt adhesive primer only, but this is also messy. (The problem is that you really need to lay the track while the adhesive is still wet, to keep the base as level as possible. Inevitably the adhesive gets all over your hands, particularly if you are forming flexitrack into curves!) For my most recent length of track, I used builder's waterproof PVA adhesive, but it hasn't been down long enough yet for me to be able to say whether it's a success.

Polystyrene foam sheet may also work as well. Your best bet is to try it! I would lay a few test lengths, one using PVA, another using roofing felt adhesive (if it dosn't melt the polystyrene), and leave them outside. A crucial decision is how you will hold the curves in shape. For long straight track sections, I glued the foam to the concrete base, and glued the track to the foam, lining it up with a sraight-edge while the glue sets. For the curving sections I have a layer of rubbercrete under the foam so that I can use track pins. If you used pre-formed curves or used curve templates to keep the curve while the glue dries, the rubbercrete could be dispensed with. In all cases, I have finished with real stone ballast and diluted waterproof PVA. The sections done this way have lasted a year so far, the sections using synthetic ballast or ordinary PVA are now bare. If done properly, the finished ballast also helps keep the track in place.