20 x 20 w 8 x 10 bedroom

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

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Quote from: Mike 870 on May 01, 2018, 08:47:59 AM
.......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.  .......

I didn't see this until today.....  The 6 inches of foam plus two separate layers of 3/4" furring with 8 inch screws doesn't add up to me.  6 + .75 + .75 = 7.5" total thickness to be penetrated by the screws, not to mention the osb or whatever the roof sheathing is. Generally speaking, you should have 1.5" minimum penetration into the underlying framing. Perhaps I don't understand how the screws are to be used; what thickness is meant to be penetrated.  ??? 

I'm not familiar with tables that would suggest the size and number of screws to use for roof sheathing + foam insulation, etc. However, there are tables for fastener size and number for foam wall insulation, installed on tthe exterior like we did when retro-insulating our home walls. Fastenmaster makes a variety of structurally rated screws and has a table for the Headlok series, for walls.   That doc is downloadable from here.  Just thought I'd mention that in case it might be of use to someone.

Fastenmaster has a large assortment of resources for their products.  I don't know about the same for GRK, but that may be only because I've never searched for any docs for their products.

Just because something has been done and has not failed, doesn't mean it is good design.

Mike 870

Thanks Nathan and Don,

I really could not find much info on this at all.  Most of what I found was on the forestry forum from guys who had build their own timber frame house.  Seems most people use SIPS, which just aren't possible on my site.  The 8 inch screws will go through 3/4 strapping then 6 inches of insulation before they bite into the sheathing boards and rafters so I guess I'm short by 1/4 inch.  I could always use a forester bit and bore out 1/4 inch of the strapping.  The screws have a pretty decent size head on them.  Once that first set of strapping is fastened another 3/4 inch will go perpendicular (horizontal) across the roof.  The second set runs the direction it needs to be for the roof.  I've got a layer of 30lb felt under the insulation, really it was because I've lost some knots and have decent size gaps between the boards in the dry winter air.


I used a spade bit to predrill all the holes through my 1x4 furring. Those screws would probably split the furring quite a bit if not predrilled, also could be a little risky trying to get the head of the screw flush with the wood. The nice thing with the spade bit is you could start all the screws on the ground, that way two hands is enough when you're trying to install.

I assumed fastenmaster or GRK would have a screw schedule for roofs like they do for walls, maybe not. The question mark is snow load, otherwise you could use the same schedule they recommend for walls.

This article is behind a paywall but would be worth a 1 month subscription or free trial. Martin Holladay will consult with engineers and professors when he writes these articles.

There is another guide called "REMOTE" that has good info on screws but I think it was mainly for walls.

I also marked the stud locations at the bottom of the wall before installing the foam. I then used a T square.. or level.. and marker to mark all my stud locations.

Some of the prep work gets pretty tedious but you really want to make it as easy as possible when you're putting in the big stuff.

Mike 870

Snow load is 20 psf, but I don't think that will really come into play here.  The only job of the screws is to hold down the polyiso and the strapping.  There really won't be much downward force.  The toughest job they will have is holding things down in high wind.   I'll need to predrill the holes.  I have some really good leftover pine for strapping the stuff is much nicer than your typical box store pine.  Almost too nice to use but I don't really have another use for it.  I have more than enough screws, so I should be fine.  I'm only accountable to myself on this build so...  heading to the cabin tonight so I can get an early start tomorrow.  Hopefully I'll have a video on the process.


Won't your siding attach to the 3/4" strapping?  If so, then those screws will be not only holding up your polyiso and strapping but also your siding.  That is a big moment arm (6.75") for so little bite into the house (1.25").  I would want more bite with so much weight hanging on the screws.

Mike 870

Here's what I got done so far.  Hopefully this picture helps it make more sense.  It's not for siding it's for a metal roof.  I still have a two foot strip to add at the top before I can finish this front section.  The screws are biting into the ash rafters, it's solid I've been climbing all over it today.  At the bottom and the sides the strapping fastens to built up 2x4's. 


That's a horse of a different color!

I think what you have done looks pretty good and if you have been climbing all over it and feel good about it, then do it to it!

Just for historical info, if someone else reads this thread and wants to copy what you are doing, I would want a little more bite with the fasteners.  In this instance, gravity is helping and the angle between the downward pull (gravity) and the fasteners are less due to it being a roof, but with siding, the angle would be 90 degrees and I wouldn't really feel comfortable with this at all. 

Mike 870

I think most people just use SIP panels on top of their roof, but my site would be very difficult for that as well as the logistics of it being a decent drive from my house.

In hindsight I would notch in some boards into my rafters themselves that run horizontally that way I have more area to fasten to because the rafters being 4 foot centers is kind of far apart for the strapping.  I have strapping on 2 ft centers but those ones only bite in 3/4 of an inch into the pine board ceiling.  I had to fasten those ones so that they would not penetrate through the sheathing.  So every other vertical strap is solid and bites into Ash hardwood, and the ones in between are not so solid but held down by the horizontal straps.   Overall all once everything joins up its pretty secure though. It's not ideal but a good learning experience. 

Mike 870

Here's yesterday's progress. I have a time-lapse of putting up the felt, strapping insulation and roof coming soon.

Mike 870

Here's the video of insulating and roofing the front side of the cabin: https://youtu.be/viabiXnrcjs

Mike 870

I took my 9 year old nephew to the cabin because he was really interested in helping.  We had a great time.  I don't have any kids of my own.  I don't know how you parents get anything done!  As much as he wanted to help, there wasn't much I was comfortable letting him do, so he ended up getting really bored about an hour after we got there... We made a short video together.  About half way through the video is when he started getting bored and barraged me with a stream of questions that is still floating somewhere over Lake Erie. 


Mike 870

Hey thanks Toyotaboy.  Here's a link to yesterdays progress.  I've got to admit I'm going slower than I expected on this project and I expected to go slow.  But fun things are coming, I'm going to order my doors and windows this week.  I hope to go down this weekend and finish the other side of that little roof, install some kickout flashing, and also finish sheathing and then house wrap it. I'm also looking forward to cutting out the windows in the bedroom.  Once I do that I will finally know if the real thing matches the vision in my head for how the space will feel.   We're hoping to get it dried in so my father in law can hunt there this deer season. 


Mike 870

Made a bit more progress on Friday.  Finished up the roof more or less, couple little odds and ends to wrap up.  Cut out the openings for my remaining windows.  I'll be finishing sheathing tomorrow and starting on house wrap.  Also taking delivery of my doors and windows so I'm renting a UHaul trailer to transport them. We ordered Marvin Wood Ultrex, really excited to see them.


Mike 870

We got our doors and windows in.   They are Marvin Wood Ultrex, I'm very happy with them. Not too happy with how much they cost but what are you going to do...I feel a lot better now that they are in, it opens up a whole new season for me to work on the interior (winter).



Looks good. It is a real treat having windows in place; light comes in, no wind.
Just because something has been done and has not failed, doesn't mean it is good design.


Very nice looking windows and doors. Better to overspend once than underspend twice.

Mike 870

We're almost dried in except for the very top of the loft side gable end.  It was a neat coincidence that we didn't get that bit done because I was treated to a full moon shining in over the loft.  I hope to get that last bit of sheathing up tomorrow and then the rest of the tyvec on.   I also have almost everything I need for my solar installation except for one 30 amp dc breaker and some #1 wire for my inverter.  I figured I could get it local at Home Depot but they did not carry it.



Congrats on getting it dried in. The windows look very nice, worth price paid in my opinion.

Not sure if you mentioned it already, are you planning on wood paneling for the walls (like the ceiling)? You are getting close to being insulated + woodstove.

I've been following along the videos too, I just keep thinking how much extra work it would be to move the camera around in addition to all the framing (not to mention editing it all together). I had thought about recording stuff before, but I think the most I'd have in me is to wear a gopro.

Keep it up.

Mike 870

Thanks Nathan, I really like the windows a lot, and the sting of the price has already worn off some.  I think we are going to do some sort of pine paneling like the ceiling. We may mix it up with some drywall in there in places as well to add some color and a change of texture.  I sometimes find that all wood can be too much pattern.  So we may throw in some drywall for contrast.

The filming really is a pain.  It requires a lot of planning and forethought to get the right shots and get set up.  But it's also enjoyable and a great way to chronicle the build.  The editing is pretty tedious.  I film a lot, and am usually compressing two or 3 days of work into 10 minutes.  I'd guess I spend between 2-6 hours editing each video after I get home.  And honestly I could spend even more time cleaning them up if I were really particular. 

Made another trip today, got the loft in the window:

Started installing the solar panels!


Really coming together. Looks great!


Love this build. Keep up the great work!

Mike 870

Mike 870

Made another video of putting in the last pieces of sheathing, the loft window and then installing the solar racking from iron ridge and got 1 panel up before we ran out of time.  My previous video kinda went mini viral, it got 18,000 views in a week, it was surreal getting so much views.


Migraine Craftsman

Thumbs up youtube brother, lol  c*