20 x 20 w 8 x 10 bedroom

Started by Mike 870, March 20, 2014, 05:52:24 PM

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Mike 870

How many inches of insulation did you go with?  My thinking is, I'm much more likely to get an R40 ceiling performing at R40 with foam.  Whereas someone with bats or blown in cellulose might get R60 performing at R 40 or so fourth.  Didn't know some forms of metal needed sheathing, thanks for the heads up.  I used structural GRK screws as a first method of attaching my rafters to my top plate.  They are pricey indeed!


Wrap and strap performs better than sprayed in between framing, I've run 5-6 inches mostly in the last decades. When Dad first started foil faced polyiso over solid roof decking in the early 70's we were putting 2" foam down over 2.25" thick wood roof T&G.
When it is dried in one of the deck cleaners with oxalic acid in it would wake that ash back up.
Half dovetail on the tie, nice  :)


We are in a regular 2 story with flat attic. We did R-23 in the walls, 2.75" on the outside - about R-15 to R-18 and R-60 in the attic. I had kept an eye on craigslist for a few months when a commercial roofer started listing the polyiso for $10 a sheet. If you keep an eye out you might find a really good deal, there are also some online retailers that sell used material that may be worth looking at.

I think if you put 5-6 inches on top you could get by with a pretty small wood stove.

The wood framing really does kill batt insulation. From memory, a 2x6 wall with R-19 batts performs at around R-10 to 13 depending on 16" vs 24", headers and all that.

The negative of thick foam - probably not as much so on the roof, but still needs careful planning, is that you have to hide it with a lot of smart flashing and trim work. It was a ton of extra work for siding, I'll tell you that...

Mike 870

Don are you needing venting over that amount of foam on the roof?  I am in zone 4 for heading/cooling.  I've been led to believe it's not needed with that thickness but I don't want to make a mistake.  I'll look into oxalic acid.  Thanks for the compliment on the ties.

Nathan I'm not looking forward to all the extra work the foam will cause.  I am going to put 1.5 inches outside my walls as well.


I've used unvented 6" SIPS on a roof here with no problems but when we do the wrap and strap roof it gets flatways 2x4's up and down the roof over the foam/over the rafters and then 5/8 osb and roofing, so that is vented. When we were doing the 2" foam back in the day we were using 3" roofing nails and applying shingle right over the foil faced foam. The foil cooked the shingles, that was when we started the sleepers and vented channel over the foam.


We went a different way here in Texas but here it is:
On top of the OSB decking, we put horizontal 2x4s spaced 4' apart so we could lay the 3/4" sheets of 4' wide rigid foam in-between.  Two layers of foam got it up even with the 2x4 and then we put the metal on.  Have 4" of spray foam under the roof deck.  With a silver metal roof, it stays nice and cool.  This is obviously a non-vented roof. 

We got the foam used on craigslist.  4'x24' sheets 3/4" thick for REALLY cheap.  Came off the roof of old chicken houses that were being torn down.  If I was doing it now, I would have put vertical 2x4s with two layers of foam in-between, then horizontal 2x4s and two layers of foam, then metal.  That would have gotten me 3" of rigid foam and almost zero thermal bridging.  No long screws needed and the metal attaches to the horizontal 2x4s. 


Mike 870

Thanks for all the pointers guys.  Once I realized what I wanted to do was called wrap and strap It was easier for me to research it.  I had never heard that term before.  Did another work trip today so here's a few more photos.  Got the other half of the ceiling in the main room and built the supports for the covered back porch.  Eventually I hope to use the rest of my Ash on cover for the Front porch.


Looks awesome. You are moving fast.

For doing my walls in foam I mainly used the "REMOTE" manual and the deep mass energy retrofit guides. The buildingscience.com website also has a lot of good info in general but you can definitely tell those guys 'think' about building more than actually building...



Mike 870

Ha, I hear you on that.  Lately I've been considering just doing exterior foam on the walls where it would be easy to do.  Mostly the North and East side of the cabin.  There are minimal windows and fewer tricky details to deal with.  Of course my biggest concern is cooling in the summer, so that wouldn't help there much.  So who knows what I'll do.  I do change my mind a lot during the process.

Mike 870

Hey guys, made a video tour of part of my property this past trip.  Also have a couple more videos I'll post once they are uploaded.


Mike 870

And here is a video tour of the cabin.  I give some thoughts on building methods and talk about how I'm framing the cabin.  It's much easier to get a good feel of the cabin via the video than pictures.  I appreciate anyone who watches and feel free to give feedback.  I'm trying to get better at the vlogging thing.  It's crazy you spend all this time learning to build a cabin and then you have to spend like twice as long learning to use your camera and not come off as a tool.  I have 4 more videos waiting to edit and upload so if you want to follow along, please do subscribe.



Enjoyed the videos and I'm jealous of your property.

Mike 870

Thanks for watching pmichelsen,  I appreciate it.


I liked the videos too.

That is a nice piece of property... the driveway is something else. Could be a good excuse for a 4 wheeler.

Very nice views and my favorite part is the complete lack of any sounds except nature.


Nice videos.  Hills are fun aren't they.  You have a longer uphill run than we do.
Just because something has been done and has not failed, doesn't mean it is good design.

Mike 870

Hey thanks for watching guys.  I'd love to get a 4wheeler...  I made a video of how my water system works: 


Mike 870

I Finish up the ceiling in the bedroom, talk about my back porch and how I'll insulate and finish off the roof.  Forgot to bring something critical to the operation...

Adam Roby

Hahaha... that totally sucks.  I wonder how hard it would be to hot-wire?  Coming along nicely though....

Mike 870

Probably not too hard but I just didn't feel like trying.  Thanks for watching...

Mike 870

I'm getting geared up to start building again.  Hope to insulate the ceiling and install metal roofing soon.  Take a walk of the land in this video and haul my camper up the hill to be ready for next trip.



Mike 870

Mike 870

Hey guys, I ordered my insulation, I have built cribbing on my roof, kind of an exo-skeleton box. 

Any last Advice before I start to wrap and strap? 

Planning on using a builders tape (whatever I can buy locally to seal the seams on the foil faced insulation).  Should I also Caulk?  If so any suggested caulk for Polyiso?  Planning to use something along the lines of 8 inch GRK screws to hold the strapping down. I have 6 inches of insulation, then 3/4 inch strapping vertically then 3/4 inch strapping again horizontally.  Then comes the metal roof, at which time I'll also be adding racking for my solar panels. 

Video forthcoming.

Mike 870

Well the insulation is now on site and ready for install and the metal roof is ordered and will be ready for pickup tomorrow morning.  I just ordered it today at 2:00!  For those interested in costs, the insulation was $2,300, Ill have about $400 in cribbing 2x4s strapping and structural screws.  The roof with all drip edge flashing, boots and screws was $1,200. 


Those screws sure aren't cheap. The manufacturer should have a table that tells you what size to use.. guessing you figured that out already.

Taping the insulation seams is a good idea - for air tightness alone. That foil is pretty fragile, You'll probably want to keep an eye on any dings and scrapes and tape them too. I was wondering about putting a layer of tar paper over top as an extra layer of protection. Metal roofing is pretty bulletproof though. Just keep in mind that any water that makes it past the metal should still drain out and not in.

My only real advice is always be roped in and make sure if you slip the strap is short enough that you don't dangle over the edge.