October 8, 2019 – David Petrina, “Timber Frame Construction”

David Petrina
Timber Frame Construction

David got hooked on timber framing after building a timber frame cabin for his family near Manning Park in 1998. Shortly after, he quit his engineering job at a high technology company and started Kettle River Timber frame construction uses timber studs and rails, together with a structural sheathing board, to form a structural frame that transmit all vertical and horizontal loads to the foundations.









Question: A friend of mine, well a neighbor of mine on Mayne Island started with cedar logs and ended up with a traditional Baltic cabin that they built in the woods in Norway for 500 years. He was just driven crazy by the inspectors and by code requirements, do you have to face that stuff too?
Answer: We do. I would say almost all construction does now and nowadays just everything has to have an engineer’s stamp on it and in general as long as we can show that, you know, it’s a degree of CYA (for those unfamiliar with this acronym, it stands for “Cover Your A$$!), I guess, they’re happy at that point. So that’s how we do it.

Question: When the Amish do their barn raising, is that the same principle that you use?
Answer: Yeah, so the Amish barn raising is the same principle. It’s the same type of construction. It’s the mortise and tenon timber frame construction. The only difference is they typically would do what’s called a hand raising. So, they’re not using a crane. They’re usually using a bunch of poles to push it up, but other than that, it’s the same program.

Question: How do you connect wood to steel?
Answer: I had a longer slideshow that kind of covers that which I give to architects, but there’s been kind of a bit of a revolution in timber frame construction in the last probably 20 years with the advent of a bunch of really fancy high-strength screws that we typically get out of Germany or Switzerland and they’re wonderful. I usually bring samples when I give a presentation, but they’re just basically heavy, heavy-duty screws. You can get them three feet long and their self-tapping. You just grab a cordless drill and as long as you got a strong wrist, you can drive those screws. So, we use hundreds and hundreds of them and they’re amazing.

Question: You read about multi-story buildings being built with wood how high can they go and would you care to comment on that?
Answer: Yeah, I’d love to comment on that. So, I think there’s a real revolution happening in construction moving towards wood construction, wood high-rises. I mentioned Brock Tower, I think it’s 18 stories. It’s the biggest in North America right now. I don’t think it’s the biggest in the world anymore. I think something surpassed it. There’s something going up in Vancouver that will go 20 stories. There are plans for 40 and even 80-story wood towers. The beauty with wood construction is it uses a fraction of the energy that steel and concrete use. It also captures carbon, it sequesters carbon, so it’s very good for the environment. And because wood so light, from a foundation perspective, you don’t have to build nearly as heavy of a foundation and from a seismic perspective, you just don’t have the inertia that a big concrete building has so, you will see in your lifetime, you will see a skyscraper, you will see an 80-story building for sure. They’re already on the drawing boards.

Question: What’s the difference in square-foot-cost between a stick home and a timber home?
Answer: Oh, I hate that question. So, it’s a lot. I would say for apples to apples, if you do everything else the same, you know you get the same countertops, the same window choices, same flooring choices, same cabinetry, for a timber frame home, you’re probably going to pay $50/square foot premium versus the same house without timber in it.

Question: I’m intrigued by the business side of what you do. How many people do you employ, where do you source your materials?
Answer: Yeah, so, I’m a bit unique. When I got into timber framing, I told my wife, “let’s move to the Kootenays and I’ll set up a shop and hire a bunch of guys and we’ll cut some timber frames.” and she just looked at me, she grew up in Toronto, she said, “not a chance.” So, I had to kind of reinvent my business model, so I outsource a lot. So, I’m a small company. I have six employees and I outsource the cutting of the timbers to a supplier up in Squamish, and he’s kind of a business-to-business supplier. So, what he does is he’s invested in all this CNC (Computer Numerical Control) machinery and he supplies a bunch of timber framers like me, and what we do is we send him our 3D CAD (Computer Aided Design), our design, and he cuts it on his machine and then similarly, I have another supplier that cuts the panels. So, what my company does is marketing, design, and then we actually go into the field and put these things together. So, I’m not completely unique, but a lot of my competitors are in the Kootenays they got a shop with, you know ten guys cutting away with chisels so, a bit of a different business model.

Question: You mentioned that you use fir, what are the other options? Do you work with other woods?
Answer: Yeah, so we predominately use fir because it’s a West Coast wood and it’s readily available, but we’ve used yellow cedar on projects before. Red cedar isn’t great, it’s quite soft and weak so, we don’t typically use it, maybe if it’s something that’s outdoor we might use red cedar. And we sometimes use a species called Port Orford cedar which is in the cedar family, but it comes out of Oregon. It’s a beautiful very white cedar. And then if you moved across North America, if you moved to Ontario, timber framers there would use white pine and oak. And in the tropics you see, you know, I know timber framers that have built with purple heart, but the predominant species in North America if you’re on the West Coast, it’s Douglas-fir, if you’re in the East Coast, it’s oak and white pine.

Question: Is your timber all kiln-dried?
Answer: We always use kiln-dried, not everybody does. A lot of timber frames still get built with green wood. Just more for cost reasons or just access to drying. I don’t like doing it because the wood changes, you know, it shrinks, it twists, it moves, joints open up, and it’s always a difficult conversation to have with a client when their timber frame doesn’t look as good as when you put it up.

Question: I was just wondering how many homes have you done? And secondly, from start to finish, how many months for an average-size home?
Answer: I’d have to count up again how many we’ve done, but I think we’re approaching I’d say a hundred projects. Most of those being homes. Some of them being, you know, we’ve done some commercial jobs. We did the big curved beams on the Safeway on 70th and Granville, but I think close to a hundred. Typical projects nowadays, I would say typically is nine months to a year from start to finish. For our part of the project, we’re usually on-site for three weeks. So, we show up, timber goes up, panels go up and we’re out of there. One of the general contractors that I used to work for shut his company down and came to work for me. And he just said, “you got a way better job, you know, you guys are Glory Boys you come in here, you know, you put your timber up, the clients are happy, you guys, the marriage hasn’t fallen apart yet, the budget hasn’t been blown yet, you walk up, you could get paid, and then I deal with the crap that happens afterwards, right?” *laughter*

Question: How long does it take an 18-story wood-framed building to burn down?
Answer: Do you work for the steel industry or something? *laughter* I will say that if you have a choice, if there’s a fire, you’re way better off in an 18-story wood frame building than you are in a steel building. The steel building will collapse much, much sooner. What is phenomenal, we call it mass timber, but mass timber has a very, very good fire rating. What happens with wood is it chars, and once it’s charred, it stops burning. I used to work in the sawmill industry before I worked in the high-tech industry and I was working in a town called McKenzie and our mill burned down, and we took all the glulams and they were all charred and black and we ran them through the planer and we put the building back up with using the same timbers. So, it actually does very well in fire.

Question: Where do you get your wood?
Answer: So, we get our wood from the West Coast. Not all timber framers use coastal wood, but it’s Douglas fir and it’s coming from Vancouver Island, it’s coming from the Sunshine Coast. We typically actually use a second growth wood. We’ve actually found second growth wood is actually a better product for what we do. The old-growth timber is a little bit unpredictable and as you start sawing and drying it, it tends to have all sorts of things going on with falling breaks and cracks in it and stuff. We do a little bit of cedar. We don’t do a lot of cedar just because it’s a very soft wood, particularly the red cedar. So, will you only use it if it’s going to have a heavy outdoor exposure where cedar performs very well, but it doesn’t work very well for the mortise and tenon joinery it’s just too weak.

Question: What are the panels made out of?
Answer: The panels are called a SIP panel or a structural insulated panel and it’s Styrofoam, laminated between OSB (Oriented strand board) and then it gets cut on a CNC machine for all the door and window openings, so it all fits together. And that burns. That will burn much better than the timber so Styrofoam burns.

Question: Do you coordinate all the trades, the electricians and the plumbers, and so on?
No! Thank God, I don’t. I always say I’m a sub-trade. So, typically the general contractor is coordinating all that. We tend to get a little bit involved with particularly the electricians because with these panels there’s a bit of a different way to wire them so, we have to hold their hands a little bit, but we definitely don’t. We leave that to the general contractor.

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