Expanded polystyrene, how does it stand up outside?

[Martino]

A bit of a silly question (yes, there are silly questions) about expanded polystyrene.

I have some fairly dense polystyrene blocks and want to create some outside structures. How does the material stand up to outside conditions - weather, sunlight etc?

My project will almost certainly be covered with soil, cement, Rowland’s Mix or HyperTuffa, so won’t just be sitting in the sun. I’ll be using it as filler (almost) for embankments.

What do you all think?

 

[Gavin Sowry]

Hmmmm...... personally, I'd give it a miss.

I had some stored, out of the sunlight, for a 'rainy day' project. It becomes brittle after a while, discolours. and once broken, leaves horrible beads of off white poly all over the place.

 

[Paradise]

If you cover it with plenty of house paint it will help make it last longer but it will eventually break down and collapse outside in the elements leaving a mess to clean up. It may be OK as a filler as long as it doesn't have to support much weight because it will compress. If used as a filler under already supported banks etc. I would wrap it in builders plastic to contain it and keep water out. Make sure the builder's plastic is also covered in soil etc. as that will break down in the sun too.

 

[Martino]

Ah. Thank you both. I think I’ll give it a miss!

I’ll stick with good old concrete, Rowland’s Mix or HyperTuffa.

Thanks again.

 

[Paul M]

They use expanded polystyrene under concrete floors for insulation, so if it's totally encased it should bexpect alright, but as others have said not really ideal.

 

[stockers]

Polystyrene will eventually soak up water if used outside - it then slowly disintegrates. I expect freeze/thaw is involved. If out of direct sunlight it should last a few years. I one saw a large model church made of the white stuff - looked good but no idea haw long it will last.

 

[dunnyrail]

Hm strange I have a building that I made as long ago as 1990 ish. Long overdue a new roof that I was only putting on my round toit list when running trains yesterday. Used old ceiling tiles (the horrible things that used to be used to disguise shot ceilings before the advent of Artex for such jonpbs) so they would have had plent of paint on one side. Building was double laminated in places with the things and both sides coated with Exterior Quality Tile Adhesive. Still going strong today except for small places where things have gone a bit busted where a Ply Roof has been held in place with nails.

 

[JeffofSpace]

Anyone tried the not expanded stuff? We used it as a base and for scenery for nscale be never thought about it for use outside. It is the same styrene they use to insulate houses in the north. I sourced it from hardware stores.

 

[stockers]

Not sure what actual material you are referring to. If it's insulation I would have thought it must be expanded to some extent - otherwise it is solid styrene sheet - like brick effect sheets or similar

 

[JimmyB]

I think we are talking Foam Board - link is to Amazon to show examples:

Amazon

 

[stockers]

Could well be - but that's not insulation and it is expanded (in the middle). It looks like the stuff mike uses to great effect so probably good

 

[Martino]

My original question was about the stuff that’s packed in boxes around frozen food (dog food in this case) that is delivered by mail or courier. Inside there is dry ice in plastic bags. It’s definitely polystyrene, rather than foam board, although it is rather more compact than the old ceiling tile stuff.

Anyway, I decided against it and sent the stuff for recycling!

 

[JeffofSpace]

Yes, I was mistaken...the extruded is certainly what I had in mind.

 

[ebay mike]

This embankment is part of Great Yarmouth's A47 western by-pass built in 1984 using huge polystyrene blocks with earth banks either side. I've watched 100 ton loads travel along it en-route to Ipswich, Lowestoft and Great Yarmouth docks. It's had a few dips develop over the years but hasn't disintegrated - yet!!!

 

[mike]

Foambords great for out door use..if painted