Timber Frame Workshop (and house...)

[Bob Cooper]

Todd...are you working with a timberframe supplier? They deal with this stuff daily i'd think and would be able to give you some good feedback. For my TF i just did normal stick construction outside of the TF and held the stud walls off the TF by 3/4" so that i could slide drywall against the studs but behind the TF posts/beams. Doesn't sound like the look though that you're after. The advantage of the approach i took is, to a normal framer most everything was what they were used to.

The other approach which is a little closer to what you're doing is the SIP panel route...but i'm sure you know how pricey they are.

[Todd Burch]

I am working with a TF supplier, but they just do the frames and erection. No build-out once the frame is up.

[Todd Burch]

TF company confirmed I got the wrap and strap correct.

[Todd Burch]

Well, for a while I didn't think it would happen, but today I'm making a purchase in the first step of actually building a TF workshop. WOO-HOO!!

The above questions about "wrap and strap" came up as I was researching how I would insulate this shop. While researching rigid foam insulation, I happened across a deal too good to pass up for insulation for the shop.

First, I attempted to price brand new rigid foam insulation. The big box stores near me sell the 1/2" thick (1/2" thick 4'x8' sheets), but I was looking for 3.5" thick stuff, and no one near me carries it. After a week of trying, (and I'm still trying, so I can do a true cost comparison), still no success. I did finally hear back from a local building supply house, although, I have no faith in their quote, and they didn't even manage to quote the exact specs I gave them. I asked about pricing for a sheet of 4' x 4' x 3.5" polyiso (assuming a volume purchase). After 3 days, they called back and told me that one sheet would cost $88.85. That would be believable if he was talking about a pallet with 13 sheets, but for one sheet, (I tried to confirm he was telling me 13 sheets and not 1, but he insisted the $88.85 was indeed a single sheet), it would cost upwards of $30K to insulate the shop. He's got to be confused.

The deal I found is on a load of once used, reclaimed insulation. Buying used rigid insulation seems to be the new thing to do. I found, and I'm buying, a tractor trailer load of used polyiso rigid insulation, delivered, for just over $5200. There is approximately 9000sf of this stuff (way more than I need) on pallets, and about 1/2 of it is new and never used, still in the factory shrink wrap packaging of what I'm primarily looking for (4'X4'X3.5"). It's all foil-faced both sides too. Based on the inventory I got from the salesman, I calculated the volume to be roughly an 8' wide, 8' tall and 35' long stack of the stuff. My dad went and inspected it before I committed to the purchase, and his impression, based on what he saw, was that the volume was twice what I calculated... but we'll see. If so, even sweeter. The load is a mix of 3.5", 3", 2.5", 2" and 1" material. Except for the new 4'x4' stuff, all the other thicknesses are 4'x8' sheets in various quantities -and mostly of the thicker varieties.

Based on an LTTR (long term thermal rating) rating of R5.8 to R6 per inch, and I am supposing this stuff has already settled out, I will have just over R20 in the walls and over R40 in the ceiling, not counting the 2X T&G wall siding and any sheetings that make of the wall or roof sandwich. I don't know if this would qualify for "super insulated" (I think it might in my part of Texas), but I will be "super satisfied" with it.

It will be delivered early next week. Pictures to follow.

TF, here we come.

[Tom Scott]

Todd,
I have to agree with Bob's approach on this with the conventional stick framing on the exterior of the TF. I think your scheme is making it harder than it needs to be, besides not really having a load path with structural members. I can send a sketch of what I'm thinking, but would suggest putting the rigid insulation between vertical studs. To cut down how much you have to cut the rigid, studs can likely be spaced out at least 24" on center since they aren't load-bearing (they still have to resist the wind load, though).
Does the TF company suggest how the posts are anchored to the foundation?

[Todd Burch]

Hi Tom. The TF company, when I get that far, will exactly specify how to design the foundation for the structure, and how the posts attach to it. I believe this company uses straps set into the concrete, and the straps lag into the not-seen sides of the posts. There will be some (3) interior posts, and I'm not certain how they are anchored. I've seen the system that Texas Timber Frame uses, where welded up metal block assemblies are set into the slab and the protruding parts act as tenons into mortises in the bottoms of the posts, and then the posts are drilled horizontally at the proper height and a stainless rod is placed through the post and metal tenon, (the tenon is pinned), with plenty of relish, and then the hole in the post is plugged. It's a very nice system. Totally hidden and would resist up-pull as well as a horizontal shock as well.

I'm not getting how conventional stick framing outside of the TF structure would be a better approach for me than a wrap and strap. Perhaps if I were hiring a typical framing crew to dry it in, it would be a better choice. Conventional framing would certainly be a larger expense due to the quantity of lumber required, and there would be substantial more effort in cutting up this rigid insulation to fit where bat fiberglass typically goes. There would be many, many more thermal breaks doing it that way.

I don't understand what you mean by "load path with structural members" either. Please clarify.

I do agree, that for running any plumbing (for air or water) and wires, conventional framing is the easy choice. There are, however, approaches to wiring and plumbing that can be taken, obviously, and I need to figure out the approach, or approaches, I want to take.

[Jim Becker]

I like what you're doing, Todd. What a great project!

[Tom Scott]

I will preface this by saying that I'm not as familiar with the wrap and strap method, so feel free to totally dismiss the following comments:

- As framed, the horizontal 2x6 T&G members on the inside are your main structural members for wind loads, and they are spanning between your TF bents. I don't know what that span is, but seems like quite far for flat boards to span. Other examples I've seen had the interior T&G spanning vertically.
- The 1 horizontal 2x4 at the top of your window ends up taking 1/2 of the wind for that wall as you currently have it framed. Those should at least span from the foundation to the ceiling beam to avoid that condition.
- You have to assume that water will get behind your siding at some point, and thus need an air space so that it can dry out and not rot. Having only horizontal straps directly against the rigid insulation will trap the water instead of allowing it to drain out the bottom. It also does not allow for air flow within the wall.
- I have read that the wrap and strap method uses less lumber, but with continuous 2x6's framing the interior of the wall I find that hard to believe. Could be, though, as I haven't checked the numbers. If you were OK with gyp board, plywood, OSB or even 1x6 on the interior, then that would be a bigger case for traditional stick framing. Since these studs are only resisting wind load and not roof or other gravity loads, they can be spaced out greater than the traditional 16" on center.

I don't want to poo poo on your plans if you've already got it figured out. This looks like a great project and one that I've wanted to do, so I'm jealous.
Keep us updated on the progress. I will be anxiously watching.

Tom

[Todd Burch]

The gable ends will probably be 10' on center (if I opt to center the big door), or, they might be 15' on center if I move the door to either side of the opening. The long side bents will 14' on center.

I was thinking the TF itself would be my main structural "member" for resisting wind loads?

For purposes of comparing wrap and strap versus traditional framing, I'm not sure you can consider my choice for an interior wall covering. It so happens, my choice doubles as both an interior surface, and an anchor point for the insulating and exterior layers. When I compare W&S versus traditional framing, I'm looking at the quantity of framing materials, and the permeability of the insulating layer, along with insulation value and the time-vs-labor equation I have to consider (I have more time vs $ to pay for others labor).

The look and feel I want is interior horizontal wood walls. While 1X6 T&G would give me the look I want, I am opting 2X6 material for 2 reasons.
1 - as a thick enough surface to nail tar paper to and a thick enough surface to screw rigid foam and "strap" boards to, and
2 - to have a thick enough surface to screw cabinets and other items to from the interior.

1X material for the latter would certainly work for most of my cabinet (or other item) hanging needs, so option 1 is the primary motivator. If anyone has ideas for saving $ going with 1X interior materials, and still providing a cost effective option for hanging the rest of the exterior on to, I would love to hear it. (I haven't done the cost comparison for vertical studs walls with 1X boards, versus 2X6 T&G.)

I'll be ordering 2X6 T&G material for the upstairs flooring and roof decking, so the walls are just more of it. I mean, who wants roofing nails and screws coming down through into the interior to spoil the look?

I agree I need an air gap. The 1X4 strapping would give me that, but it's laying flat and would not promote top-to-bottom air (or water) flow. Perhaps the solution here is putting the strapping on at a 45 degree angle? Need to check into this option.

I would think I could even use 2X4's in a vertical framing (traditional) manner, even on 4' centers, since the rigid foam will assist in the support of the top plate. As I have it drawn now, I'm essentially doing this anyway, just on the horizontal and not vertical. Vertical studs might be better, since the siding will be hanging on it. I would think the foam would participate quite up a bit on either vertical or horizontal framing, but I'm not an engineer either.

Good discussion. Making me think through this.

[Tom Scott]

Yes, your timber frame structure will be designed for overall stability to resist wind loads, but your wall system has to get the load to the frame. When the wind hits your building, the first thing that is affected is the cladding. From there it has to get to the TF structure, thus the wall system has to span and distribute the load to the frame. It won't be required to support gravity loads or to act as a lateral shear wall, though.
Insulation is obviously a big concern for you, and that is not my specialty so I don't want to steer you away from the efficiency you are seeking. The key is getting all the systems to work together the best way possible and I think you are on the right track. At least you are thinking about it all now.

[Jim Andrew]

It would be cool if you could post pics of the project. I like the idea of the foam insulation, have seen stories of similar foam filled walls and they said they have no gaps so it keeps the building from burning down if you have a short in your wiring, as it keeps air out of the wall. I'd be tempted to use 30 lb felt for housewrap, to minimize any leaks from siding. I took down a church a couple years ago, and the lap siding leaked to the point the boxing was all warped. It had plain paper between siding and boxing. There was a section that had 30 lb felt between, and the boxing was like new.

[Todd Burch]

It would be cool if you could post pics of the project....

You mean like, what I've been doing?

I'm 1/2 way around the planet right now, but the insulation was delivered yesterday.

photo.jpg

[Todd Burch]

A few issues with the insulation, but the used-insulation-broker says he's going to make it good.

Paperwork started to get this project officially underway…

[Todd Burch]

This post is about loft doors. Not sure what to do here. I've been playing around with a design that might work. Opinions solicited.

The loft door openings in the shop will be 4' x 7'. There will be 2 doors per opening. The doors would open to the interior.

The door openings would be framed with 2X8 material. At the bottom, the exterior sill will be angled at about 15 degrees down.

My door design starts with a box frame out of 3/4" material. Basically, 1X4s joined well at the corners to create a frame 2' wide x 7' tall. That frame would be filled with 3.5" rigid foam.

On both sides of this frame, it would get covered with 1X6 T&G pine, nailed and poly-glued to the frame.

SketchUpScreenSnapz010.png

I would apply some fake strap hinges to the exterior. As high as these are, I suppose I could even cut them out from 1/4" pine and paint them black. I don't show a piece of vertical moulding nailed to one of the doors to keep driving rain from entering where the doors meet, but it would be there. I would also have to bevel back one of the door inside edges so the swing would work out properly and not bind or rub. 5 degrees I believe.

SketchUpScreenSnapz009.png

The interior would just be utility grade strap hinges. I don't show any hardware, but it would probably just be a screen door handle one one door and a katy bar across both.

SketchUpScreenSnapz011.png

I also didn't take the time when drawing to allow for side-to-side clearance. I did leave 1/4" between door casing and the top and bottom of the doors.

I think they would be pretty cheap to build and be adequate. What do you think?

Todd

(I've attached the .skp file too)

[Jamie Buxton]

This post is about loft doors. Not sure what to do here. I've been playing around with a design that might work. Opinions solicited.

The loft door openings in the shop will be 4' x 7'. There will be 2 doors per opening. The doors would open to the interior.

The door openings would be framed with 2X8 material. At the bottom, the exterior sill will be angled at about 15 degrees down.

My door design starts with a box frame out of 3/4" material. Basically, 1X4s joined well at the corners to create a frame 2' wide x 7' tall. That frame would be filled with 3.5" rigid foam.

So the rigid foam is wedged tightly inside the frame? That is, the foam is structural: it resists the urge of the rectangular frame to wrack into a parallelogram.