Constructing Exterior Walls for Small Timber Frame Cabin

[CJ]

   Good Morning One and All,

  After a very long winter here in Northern Ontario, and having spent much of it in my garage constructing a 14' X 18' timber frame cabin, I am now down to my final two pieces of the puzzle (top plates) and hoping (fingers crossed) the it all goes together without a hitch. 
  That being said, the next phase of this project will be to construct it on my waterfront property and enveloping it with insulated walls and roof. That! is where I am in the dark on how to approach this process. 
  When I took my timber frame courses in May of 2018, we learned how to construct two different structures, but never learned how to build the exterior wall and how to finish it off. I have looked on line for videos, but haven't found any to provide some sort of guidance. 
  Can somebody instruct me on how to; build an exterior wall and how to insulate it? How to get a finished wall (drywall) in behind the girts? Do you install drywall first and then install the frame around it? 
  One thing that was mentioned on course was, that if drywall is installed, then (5/8') spacers are to be put on the posts and the drywall isn't to be attached to the timber frame structure. That's all fine and dandy, but how to I put drywall up without supporting it, taping and mudding it, and then building the frame after that? Very confusing indeed! 
  Any advice or info that can be provided from any of the members here, it would be certainly be welcomed. I dread this part of the project because I am absolutely in the dark with this process. Thanks very much!!

   Cheers!
   Chris 

[Hilltop366]

I would be reluctant to put drywall in a seasonal building that is not being heated during the winter, (edit: around here) it would tend to hold moisture and cause the crack fill to pop around the nail or screw heads. A solid wood product (t&g boards) would be my first choice.

For insulating do a forum search for "wrap and strap".

[ballen]

I am planning a similar size build. Just like I did with my outhouse, I plan to build the frame, line the outside with barn wood, put 2 layers of 2" polyiso then nailers and board and batton.  You see the barn wood on the inside but thats what I'm after.

[Hilltop366]

Sorry, I never answered your question about hanging the drywall, I used 5/8" spacer blocks in between the timber frame and the stud wall then after exterior walls were finished I slid the drywall behind the timbers. I found it easier to run the drywall horizontal and do the top piece first then the bottom.

I also know a guy that put the drywall on the stud frame and then stood the wall up, but because the building inspector wanted to see the stud framing and the electrical inspector wanted to see the wiring before the drywall was put on he built the walls standing up and had the electrical installed and inspections then unscrewed the walls at the corners and laid them down to install drywall and then put back up. 

If your building needs to be inspected at various stages of the build I would recommend talking to the inspector about you plan of construction and find out when and what they need to see so there are no surprises for either party later on.

[CJ]

The reason I was leaning towards drywall, is that I am going to have T&G for the ceiling and the wife doesn't want the entire inside of the structure to be wood lined. She wants contrast. I tend to agree that too much wood in the interior can be somewhat overwhelming, hence the drywall idea. If there are other alternatives, then I am open to ideas.
So, back to the completing the walls...if the 2X framing goes up and you say slide the wall panel in behind the posts, how is this done when there are girts 3' from the floor? So my thinking is that I do one bay at a time with the wall finish and then stick each stud into place between the sill and the top plate rather than build a section and try to fit it into position in the hopes that it'll do so without complications. I presume that the 2X's get fastened to the top plates and secured to the foundation sill plate? This is all new territory for me, so I need a general understanding on how to envision this. 

[Hilltop366]

Other than painting the boards I'm not sure what else there is, could check with your building supply store.

The girts 3' from the floor would make things more challenging for sure, if I recall it was not much fun wrangling the drywall behind the post without the extra girts.

Wondering if a person could tack the drywall up to the frame first then build the stud wall and attach the drywall to the stud wall after?

I did all my wall framing by myself I would not have to lift wall sections, I did frame it one stud at a time.

I would start the usual way by laying out the top and bottom plate and marking all the stud and window and door locations, next fasten the bottom plate then nail the corner studs together and stand and brace them up (toenailed at the bottom) next nail together the window and door openings and toenail them into place. Then add the rest of the studs. Add a temporary horizontal board or strapping with all the stud locations marked on them (a bit above 4' if you are using plywood or osb sheeting for exterior) then put on first top plate and make sure the top plate is straight (I was taught to use string and blocks for this but really you will be fastening the stick frame to the timber frame so it may not apply) and add second top plate with over lapped corners. 

I hope this makes sense and helps.

[Brad_bb]

You haven't said whether the cabin will be conditioned air all year round?  The biggest enemy is moisture.  Moisture allows mildew on drywall, in fabric etc.  You've got to control humidity all year round inside.  You often do that with the same devices that control temp.  

The ceiling T&G is typically nailed or screwed onto the timberframe before any walls go up. Then roof paper over that.  Next you've got to think about how you will get electrical in that T&G  ceiling for lighting.  I did that by creating a 1.5" chase/air space between the t&g and the next part of the roof by putting horizontal 2x4 blocking across the roof every 2 feet.  Cut out the spacers wherever you have to run conduit.  I like to use Sips on the roof so those go on top of the spacers and screw through the sips to the timberframe.  Then you put roof paper on those(I use Titanium UDL50).  Next you create a cold roof by running 1x4's vertically on the roof every 2', then run them horizontally over those creating a square grid.  It's important that the first layer on the sips runs vertically.  As a cold roof, should any moisture or condensation occur in the cold roof, it has to be able to run down the roof, which is why the first set runs vertically so as not to impede that.  Then you can sheath the roof and install your roofing material.  For walls I build 2x6 framed walls and later will spray foam them with 1.5 inches of closed cell, then open cell on top of that.  The reason to do framed walls is that you will often end up changing electrical or moving it as you go along and it's a lot easier to do that in a framed wall than in sip walls.  I don't use wall girts as it seems you are.  So I use a 3/4 or 5/8 spacer on the outside of the timberframe so I can slip in drywall after.  Do you really need wall girts on that frame of yours?  Typically in a structure like that you don't need them for strength.  In old barns, they needed them as a place to nail siding to.  If you want them for looks, what if you install them after your drywall by slipping one end in the lap mortise, and don't use a tenon on the other end just screw it to the post with a pocket hole screw from underneath?  Kreg is making a larger screw for decks or something and it's much heavier than the standard.  Just a thought.  Are you pouring a concrete foundation once you determine your wall and siding thickness?  Will you have a stone lug on the foundation for 18 inches of veneer stone so that your siding is not close to the ground where it would stay damp or catch a lot of dirt?  




 

 


 


  


 

[CJ]

Hilltop366
  Thanks for your point of view. Your process on how to frame the exterior wall one stud at a time was the way I was going to go about it, rather than build the a section of wall and try to fit it into place after. It would seem to prove to be a bit difficult, in my view. However, being a first-timer, I am not 100% sure of that.

Brad_bb
  The cabin will not have air conditioning, as it will not have power right away (new property with no other structures on it) and possibly at a later date, if and when I get around to building a small cottage (that's the plan). I might go with a small solar array with an inverter, but not big enough to power an air conditioner. So now that you've mentioned about the moisture, then maybe drywall is not the approach to take. 
  Thanks for your step-by-step approach and your pictures! The pictures alone are worth a thousand words. That certainly helps in giving me a better idea on how to go about proceeding with enclosing the frame. One question; what is the difference between open cell and closed cell? 
  The reason I have girts is that's what the plan called for. The mortises are already made as are the girts, so leaving them out altogether probably isn't a good idea aesthetics wise. I could, as you say, open one end and install it after the fact. I'll play it by ear.
  As far as the roof goes, I will T&G it in the manner that you have pointed out and once my roof paper is on, I will either sheath that with a layer of plywood and then install two or three layers of 4'X8' SM board laid out in a manner where the butt joints from the meeting of two pieces are, I will then overlap them with another board to eliminate having the same gap meet there creating an avenue for air leakage. If I add a third layer, then I will run that board horizontally and in a manner where no added meet existing joints. That may require some cutting of the board lengths (if that makes any sense to you). 
  All I know is, it is now June 1st and I haven't got my slab on grade yet, and I have been waiting on a quote from a contractor in my neck of the woods where I plan on building this frame. My window of opportunity is a short one here in northern Ontario (June, July, August and maybe September), so time is of the essence. 
  Thanks for all of your input and advice. The pictures were absolutely a big help. Maybe for future reference and to help out other greenhorns, someone would actually video tape a full build and put it on line? I know it seems like a huge undertaking to set up a camera every day, have to edit it, maybe in a time-lapse manner, but the idea would be immeasurable for someone just coming into this type of work. Maybe I could even do it. !

[Don P]

If you don't control moisture I'm not sure that paperless drywall is any more likely to mold than wood paneling. We don't have ac here in the humid mountains and by the end of summer it is the woodwork that is in need of a good wipe down not the paper faced drywall. Nowadays you can go one step better and avoid having that organic paper facing. There are paints that have mildew inhibitors in them so I don't think it is a non starter. One way to lower the relative humidity is heat and vent. Raising the temperature a very few degrees lowers the rh, stirring the air and venting that moisture prevents damp from settling in to cool spots, that can be solar and pretty simple, think of principle of the solar dry kilns on a much reduced scale. That is much easier in an unoccupied building. Since we live in this house full time we do things backwards for people comfort, intaking cool damp air all night and then shutting down the house in the daytime letting that moisture settle on surfaces. One solution there still short of ac is running a dh but as in any kiln the laws of thermodynamics rear their head, that drives up temps as well. Anyway, just stuff to ponder.

[Hilltop366]

I was thinking more of being unheated in the winter being a problem with drywall, in my area seems like the change in temperature and humidity tends to cause wood movement problems with the drywall compound cracking and then the moisture will rust the screw heads. It is recommended to keep the minimum temperature above 12°C to help reduce problems with walls sweating in the winter around here.

This is what can happen around here with big temperature swings and high humidity in the winter depending on which way the wind is blowing, humidity may not be a problem in North Ontario winters where I suspect the winter air is much dryer.

I guess one has to take in their local climate and conditions to make a decision.

[Brad_bb]

If you're going to all the trouble with 3 layers of polystyrene panels, why not just install SIPS on the roof?  Given your short window of time, it would be a quick install.  

[CJ]

I haven't ruled that option out either, Brad. There's a company out there called EZ Sip in where they provide a polystyrene type product with slots at 16" centres that will accommodate 2X (4 or 6) studs and come in 4'X8' sheets that can be custom length depending on your situation. I was eyeballing them, too! Pretty neat really.

[Don P]

I would cost it out, the foam goes on quick, especially at that size.

This was 3 layers of polyiso on an 18/12 pitch, seams offset, sleepers, ply, shingles. The foam took a few hours, it was probably the most minor part of the labor on the roof.

[CJ]

Wow! Steep slope. Did you glue each layer of polyiso as you went along? I kinda played around with that method in my mind. Install one layer of foam board, then add a second layer, but laying the board in a manner where the seams from the first layer are overlapped with the foam, and then doing the same for the third layer. Meaning, the seams will not be matched up to those seams on the layer below. This would alleviate a channel that would allow air in or out of the building. Then install a layer of plywood and screw it down to the rafters sandwiching the foam board, then follow that up with sleepers. Maybe I have it backwards, I'm not sure? I've only mulled this over in my mind. Again, being a first-timer, I am totally in the dark with how to proceed with finishing the exterior. Hence the reason I have turned to this forum to get a much better idea from those who have the experience and the knowledge to lend to the inexperienced.

[Don P]

Yeah above a 12/12 I call a rain splitter roof :D. Dad's whole career was the age of the 4/12 roof, the minute I started working out on my own 10/12 and up became popular.

There was a "dam" at the bottom of the insulation on the roof, built up of flatways 2x4's and ply, this one was 5" total, 2 layers at 2" and one 1" layer so I must have had 3 layers of 2x and one layer of 1/2" ply at the bottom. A vertical 5" ripped 2x6 up the rake edge of the foam and a 5" rip with a 2x4 screwed to its side flat to make an angle up the overhang rake edge as a subfascia. The 2x4 flatways there was deck screwed to each piec of 2x T&G roof decking to hold them up tight to the sub.

The first layer of foam was ripped 2' wide for the first row and the first piece was 4' long. Second layer began with a full sheet then the third layer went back to the layout of layer 1, so just as you were thinking, offset the joints. You can use tyvek tape on the seams, I can't remember if I did on that one. No glue, I did use some nails to hold sheets temporarily then worked my way back across nailing the sleepers to the back of the bottom subfascia, screwed to the dam and thru the foam and deck to each rafter which were on 4' ctrs and using shorter screws just thru the foam and into the deck for the sleepers in between, so the sleepers were on 2' centers even though the rafters were on 4' centers. Then nailed the ply over that. My vent channel was under the ply, over the foam. This was shingled but I do the same for metal. I feel it works better to seal the metal to the sheathing and vent under the ply, this avoids condensation on the underside of the steel. You'll find opinions either way there, read the manufacturers recommendations as well, some styles and weights require a solid deck others do not.

[CJ]

  Don, as much as I appreciate your detailed step-by-step process, you are telling it to a guy is not fully comprehensible about your technical guide. Things like dams and rake edge are all new terms and I'm trying to visualize what they are.  :-\
 

[Don P]

A coupla pics will hopefully be worth more than trying to do a word picture. I started drawing this awhile ago for another FF'er I was pm'ing with, his is a purlin roof but the insulation and sleeper concept is the same so I grabbed that file and sketched a little more on it, laziness but hopefully it'll work for our purposes.

The ridge of the roof, you understand what that is, the eave is the bottom horizontal edge, the rake is the roof edge along the slope between the ridge and eave. Other terms you'll hear on a jobsite are eave soffit and rake soffit, the underside of the overhangs along the eave edge or the rake edge

This is looking from the eave end. Not sure if it'll be legible in the post, the labels read sleeper, insulation dam (same height as the foam), overhang vent intake area (put soffit vents here), eave subfascia, rake subfascia (they are 1-1/2" taller than the foam). You'll nail or screw the finish fascias to the subfascia, they are framing. Sheathing ply goes over the subs and sleepers, air intakes into the soffit vents runs up along the sleeper area and exits a ridge vent;





A shot from the ridge looking down slope showing the end views of some of the framing. You can see how I make an "angle iron" subfascia out of wood along the rake edge. I screw the flatways 2x4 to every projecting piece of T&G on a rafter roof. In reality on a purlin roof I would just use timber screws into the purlins from the eave subfascia so kind of ignore the purlins here. You can see the eave insulation dam and cap sleeper over the outside of the wall. You can omit that and run the foam all the way out to the sub, its about six of one on cost by the time you factor labor vs materials.

[CJ]

Now those pictures are really helpful in defining what you were trying to convey, and certainly a big help in what I require in my build. I kind of had this idea in mind, but seeing it in a drawing just solidifies how I should go about doing it. Thanks so much for your time and explanation. As I have stated earlier, looking to the experienced guys for much needed guidance is a valued asset here on this site. Great job! Thanks!!

[CJ]

Does anyone think that I should put some kind of preservative to help prevent the invasion of insects such as ants or other little pests that have a tendency to show up without an invite?