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XPS foam for permanent cover?

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#1 Rac19

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Posted 05 October 2020 - 12:22 AM

I am thinking of adding an insulated, permanent cover to my permanent pier. A material that I am considering is extruded polystyrene (XPS), 30 mm thick. It seems to be easy to work, reasonably rigid and to have good insulation properties.

 

I am thinking of a 900 mm x 900 mm x 600 mm box, glued with silicone sealant. I would probably cover it with reflective insulation secured with contact glue. There would be a suitably sized plywood base on the pier to fit it to.

 

My question is, has anyone used this material for this purpose? If so I would be interest to hear any thoughts.



#2 speedster

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Posted 06 October 2020 - 12:48 AM

Howdy Richard!

 

The sun eats XPS, as well as the other foams. You might consider Polyiso panels.  They come with foil faces on both sides so the sun thing is not an issue.  A little more flexible than XPS but plenty stiff for what your need.  You can pin your joints with 16D nails and then cover the joints with foil tape.  Big Box stores stock it.  Loctite and PL make an adhesive specifically for XPS.



#3 Rac19

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Posted 06 October 2020 - 01:48 AM

Howdy Richard!

 

The sun eats XPS, as well as the other foams. You might consider Polyiso panels.  They come with foil faces on both sides so the sun thing is not an issue.  A little more flexible than XPS but plenty stiff for what your need.  You can pin your joints with 16D nails and then cover the joints with foil tape.  Big Box stores stock it.  Loctite and PL make an adhesive specifically for XPS.

Thanks for the advice. The purpose if the post was get feedback such as this.

 

I was definitely going to cover the XPS with a reflective insulation and seal any joints gaffer tape or similar. The Polyiso panels, with a skin already attached, sounds appealing and the product is sold here. There is a 1" (25 mm)  thickness too, which I think that I would prefer.



#4 Rustynuts

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Posted 06 October 2020 - 03:20 PM

silicone does not stick to XPF board!



#5 Rac19

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Posted 06 October 2020 - 03:50 PM

silicone does not stick to XPF board!

Thanks, I can see that I will need to find a suitable adhesive such as the Loctite PL product already mentioned.

 

I am also looking at FoilBoard which is EPS with aluminium foil each side.



#6 Rac19

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Posted 19 October 2020 - 07:22 PM

After some thought, I have decided against a foam box. We occasionally experience large, destructive hail stones that could rip a foam box to shreds. They can be "golf ball" size and even larger.

 

I am thinking now of using 6 mm marine plywood. Thicker would be stronger but weight could start to be a problem. It would weight 10 kg as it is and, being quite bulky, it would difficult to handle. For this reason I would hinge it at one end, to a 12 mm plywood base fixed to the pier. I will possibly use lift-off hinges.

 

I the short term at least, sun protection (and waterproofing) would be achieved by covering the box with a plastic/reflective telescope cover that I have. Later, I might consider gluing an insulation foil to the outside of the box and possibly some thin foam insulation to the inside.



#7 speedster

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Posted 20 October 2020 - 03:51 PM

No need for marine ply.  Same adhesive as exterior grade.  The difference is in the plies.  Marine does not  allow knots and checks in the inner plies so that it bends uniformly.  Some other minor differences in plies as well.



#8 Rac19

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Posted 20 October 2020 - 07:59 PM

No need for marine ply.  Same adhesive as exterior grade.  The difference is in the plies.  Marine does not  allow knots and checks in the inner plies so that it bends uniformly.  Some other minor differences in plies as well.

Thanks. I will check the pricing of exterior plywood to see how much it saves. The marine ply is quite expensive. The absence of knots might just make a difference in a hail stormsmile.gif. The worst storm in this area (30 years ago) had hail stones the size of tennis balls that shattered roofing tiles


Edited by Rac19, 20 October 2020 - 08:04 PM.


#9 Rac19

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Posted 24 October 2020 - 06:43 PM

I think that I have made a decision to go with a 1000 x 810 x 660 cover fabricated from 6 mm plywood (probably marine grade). Because thin plywood difficult (impossible) to join, 30 mm square wood will be glued and screwed for all joins. I will probably line them box with 30 mm thick polystyrene foam or Foilboard. The cover will be painted for sun and weather as well as to help it blend into the yard (hopefully).



#10 jcj380

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Posted 30 October 2020 - 11:42 AM

Have you considered an XPS "sandwich"?  Thin veneer glued to both sides of XPS sheet.  Two-inch is popular for lightweight model railroad benchwork.  The veneer would still have to be waterproofed.  Just a thought...



#11 Rac19

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Posted 30 October 2020 - 05:13 PM

Have you considered an XPS "sandwich"?  Thin veneer glued to both sides of XPS sheet.  Two-inch is popular for lightweight model railroad benchwork.  The veneer would still have to be waterproofed.  Just a thought...

Thanks for the suggestion. I did find foil faced polystyrene (FoilBoard) which I don't think is as strong as XPS.

 

As mentioned, I am concerned about large hail which can smash roof tiles on rare occasions and I assume that either type of foam board would be less resistant than tiles. I have started work on the plywood solution, which will be lined with foam board if necessary.




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