XPS thickness - can’t find 3/4in. Change build plans?

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XPS thickness - can’t find 3/4in. Change build plans?

Postby jacr » Fri Dec 27, 2019 7:25 pm

Hi all,
I’m planning to build my first trailer. The idea is a pseudo-standby-squareback with a queen size bed and a bunk for our little one.
After reading many posts from the forum I decided upon 1x2 framing with extruded polystyrene infill and 1/8” Baltic birch inside and out, probably with an aluminium skin. In my stupidity I didn’t check that 3/4” XPS was available - it seems like it isn’t - I’m in Canada. So a few options that I can think of: 1) increase thickness of framing - I already purchased 1x2 (3/4” thick) but I could add some 1/4” ply and then purchase 1” XPS; 2) is it possible to pass 1” XPS through a thickness planer to create 3/4”? I know people use power planers on the same stuff when making surfboards; 3) use something instead of XPS.
I’m hoping the voice of experience may be able to guide me.
Thank you,
James
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby tony.latham » Fri Dec 27, 2019 7:53 pm

Take a look at Tom and Shelly's build thread. They too had that problem.

http://www.tnttt.com/viewtopic.php?t=70278

They built a hot-wire foam cutter and lived happily-ever-after.

:thinking:

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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby John61CT » Fri Dec 27, 2019 8:22 pm

I'd revise for thicker walls.

IMO 1" is minimal anyway especially for Canada
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby tony.latham » Fri Dec 27, 2019 8:46 pm

IMO 1" is minimal anyway especially for Canada


I doubt a human can tell the difference 1/4" of foam board makes in a teardrop cabin. The advantage of 3/4" walls is that you can use a skeleton made from 3/4" plywood or 3/4" thick boards. And I think that's huge.

Image

Teardrops require good ventilation. Even when it's below freezing you need to crack the vent on the roof and have one window down at least an inch. Insulation in the walls precludes condensation. 3/4" or 1" in the walls? It won't make a difference.

:frightened:

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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby jacr » Fri Dec 27, 2019 8:58 pm

Thanks Tony. Tom and Shelly's build thread was a great suggestion. The wire cutter looks like a feasible solution. It may slow the build down while I locate parts but it seems like it would work better than the thickness planer!

I’d be happy to increase wall thickness if there was an added benefit for comfort but otherwise it seems like a real PITA.

Thanks again.
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby Tom&Shelly » Fri Dec 27, 2019 9:12 pm

jacr wrote:Thanks Tony. Tom and Shelly's build thread was a great suggestion. The wire cutter looks like a feasible solution. It may slow the build down while I locate parts but it seems like it would work better than the thickness planer!

I’d be happy to increase wall thickness if there was an added benefit for comfort but otherwise it seems like a real PITA.

Thanks again.


Somewhere in the thread I linked to a site that describes how to build it, and also sells the transformer and wire. We built a 6 foot long bow so we could (and eventually did) cut our roof. You may want to consider a smaller one for the wall work, so that it is easier to handle. The wire may want to expand and droop if you aren't careful. Generally, we are very happy with our results.

Tom
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby Squigie » Fri Dec 27, 2019 10:16 pm

Call around.
Check with building supply places, insulation companies, and even businesses less commonly associated with XPS - like plumbing suppliers, electrical suppliers, HVAC companies, and where I finally found someone to order 3/4" for me ... overhead door companies.

We couldn't get 4x8 sheets without ordering an entire unit (64 sheets?), but 2x8 sheets were a reasonable price. And, since the overhead door company was ordering a truckload of insulation anyway, I didn't have to pay anything for shipping.
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby jacr » Sat Dec 28, 2019 8:44 am

Thanks Squigie. I’ll call around this morning. I tried the big box stores and sent a message to Owens Corning to ask who they supply. You made some good suggestions.
Back up plan is the wire cutter.
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby tony.latham » Sat Dec 28, 2019 10:42 am

We couldn't get 4x8 sheets without ordering an entire unit (64 sheets?),


Squig:

There's a big tall pile of them up here in Salmon at the lumber yard. There's a dust layer from when I bought my three sheets in May. I felt like I'd found bricks of gold.

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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby rjgimp » Sat Dec 28, 2019 1:10 pm

A hot wire is a far better idea than a planer. OP827 used a planer on foam sheets in his build http://www.tnttt.com/viewtopic.php?f=50&t=61344 and ended up with bags and bags of fine foam dust. Even with a vacuum it will get everywhere.

Is 1.5" available where you are? A well designed hot wire could neatly split that in half with no waste.
-Rob


I hope to make it to a Procrastinators Anonymous meeting someday...
just as soon as the steering committee gets around to scheduling one!
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby Squigie » Sat Dec 28, 2019 2:45 pm

tony.latham wrote:
We couldn't get 4x8 sheets without ordering an entire unit (64 sheets?),


Squig:

There's a big tall pile of them up here in Salmon at the lumber yard. There's a dust layer from when I bought my three sheets in May. I felt like I'd found bricks of gold.

Tony

Yea. I've been tempted to go grab some, a couple times when you mentioned it. But between fuel, time, and my lack of appropriate transport method, I didn't think it would be viable.
The best way for me to transport 4x8 sheets would be strapping them to the roof of the pop-up tent trailer. But towing it up and back would further increase fuel costs and time. (I have a self-imposed speed limit of 62 mph with that trailer.)
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby jacr » Sat Dec 28, 2019 6:36 pm

I did some more searching online and calling today. Neither the big box stores nor some smaller building supply stores carry it. However, I did find some specialty places that cater to tradesmen and they look more hopeful. I’ll call on Monday when they open.

I can get 0.5, 1.0, 1.5, 2.0” so cutting 1.5 in half may work.

Thanks again.
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby John61CT » Sun Dec 29, 2019 3:42 am

don't y'all have cheap truck rentals round there?
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby jacr » Sun Dec 29, 2019 7:23 am

John61CT wrote:don't y'all have cheap truck rentals round there?


We have UHaul or Budget Trucks. Are they a good source for XPS too?

EDIT: sorry - I didn’t realise you were replying to squidgie’s post :lol:
Last edited by jacr on Mon Dec 30, 2019 9:41 am, edited 1 time in total.
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Re: XPS thickness - can’t find 3/4in. Change build plans?

Postby John61CT » Sun Dec 29, 2019 12:28 pm

Was in response to

Squigie wrote:
tony.latham wrote:
We couldn't get 4x8 sheets without ordering an entire unit (64 sheets?),


Squig:

There's a big tall pile of them up here in Salmon at the lumber yard. There's a dust layer from when I bought my three sheets in May. I felt like I'd found bricks of gold.

Tony

Yea. I've been tempted to go grab some, a couple times when you mentioned it. But between fuel, time, and my lack of appropriate transport method, I didn't think it would be viable.
The best way for me to transport 4x8 sheets would be strapping them to the roof of the pop-up tent trailer. But towing it up and back would further increase fuel costs and time. (I have a self-imposed speed limit of 62 mph with that trailer.)
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