Other Trusses - Arrow Timber Framing

Mono truss, Box truss and Multi Web truss

These three trusses are uniquely different, but they share a lot of overlap from a stylistic perspective. So for your convenience, I’ve grouped them together. How do they share style overlap? Answer: With rustic, modern and industrial influence. Let’s break down these three adjectives one at a time.

Rustic – Even if you were to paint all of your timbers bright white, you would still have some rustic influence simply from the geometry and presence of the square boxing shapes punctuating otherwise flat surfaces in a structure. Geometrically, sharp straight lines and edges represent strength. Curves represent elegance. For example, compare posts that are embellished with curves or softened in some way with standard straight posts. Or consider the change in appearance when round Geco-Roman columns replace square posts. There is just something raw and basic when the “bones” of a structure are visibly celebrated rather than hidden behind drywall. In general timber framing or post and beam construction represents warmth, belonging and security.

Modern- By definition, Modern is always changing because it is keeping up with the times, always on the cutting edge of what is possible with design. One hallmark of Modern style is, SURPRISE! Modern design uses surprising, charming or good looking ways to combjne different building materials to create a unique look and feel. Another hallmark of Modern style is mixing old and new. I once seen bright red heating ducts suspended from old multi-web timber trusses in a commercial restaurant space. This used both of these Modern design principles.

The Box truss was used for a lot of old commercial construction and subsequently many penthouses and offices display a modern style of old and new. The Mono truss plays well with simple, single plane roofs sloping outwards towards a view or up to capture light.

Industrial- We have already touched on ho w some of the Industrial look has evolved in discussing the Modern influence above. All three of these trusses have what you might call unorthodox beauty. You see unorthodox or unique beauty with a lot of movie stars… you might say perfection can get boring! This concept is the driving force behind the use of raw industrial elements and features used in Modern designs today.

While these three trusses capture imperfect beauty on a bigger scale, you can also use rough industrial touches on the trusses themselves. Such as rusted metal work or heavy cables with crude functional clamps. You are only limited by your creativity accent!

Lastly let’s talk about some Span limitations. The multi Web truss has the biggest load capabilities, precisely because of the many truss webs. Many old warehouses have spans of 60-80′ and have held up well. Today’s engineering criteria may limit the span or require beefier timbers. The Box truss capacity is limited by its height. The taller the Box truss the greater it span capacity. I remember one project which had a relatively light snow load. It had many 30″ tall Box trusses 4′ apart with a span of 28′ or 30′. With the webs at such a low angle, metal connections were required to address the big tension loading. The Mono truss has similar constraints as the Box truss. Sometimes the Mono truss is used in a unique way. A big supporting Mono truss as a centerpiece underneath and upwward sloping ridge/hip has produced a great look. So maybe one of these 3 trusses will work for you? Or maybe just a creative piece of what you’ve learned here? There are many things to discover and utilize regarding imperfect beauty!

Arch Truss

Technically this truss should be called by it’s specific name with arched members. i.e. A king truss with arches or a queen truss with arches etc. But who has time for that, with everyday communication? Clients and professionals alike, latch on to the easiest name available. The clear winner has been simply Arched Truss!

And it is a very popular truss indeed. Why? Without a doubt, it has to do with softening the rustic strength of the timber trusses. You might say everyone is seeking a balance between rustic and elegance, with ALL of their building choices, from timbers to cabinetry to colors. Timber arches provide a big “influence dial” to adjust that rustic/elegance balance. Here are some popular arched truss applications for your inspiration.

Arched King Truss

This truss can be done with or without webs. And the arched bottom cord can be made slimmer in the center- this slimming has a lightening effect, reducing a heavy rustic feel. Not that it is better, but sometimes it just seems to fit better for different situations and style taste. That goes for the webs as well. Sometimes less is more- no webs might look better. Sometimes straight webs with arched bottom cords is the answer to the client’s taste. Sometimes arched webs and sometimes webs with a single arch find the sweet spot.

I remember one outdoor living project review with the clients. We gave them the options of arched webs and no webs. The lady liked both options, but didn’t get an absolute YES from either option. On a on a whim, we made the webs straight. That did the trick! That achieved the right rustic/elegance balance for her.

Arched King/Queen Truss

Here are a couple of options which utilize uniquely positioned Queen posts on each side of the King post.

Sometimes people want a high elegance factor and a high rustic factor. This solution with added beef and vertical support to the bottom of the truss do exactly that, with the rustic girth and soft arches. It also works well for a high ceiling space to add a cozy warm influence.

Arch Scissor/Queen Truss – This truss is not particularly strong without a tie rod collecting tension loads from Queen post to Queen post. But it is an attractive solution for a lot of different situations, as it captures a piece of the hammer beam truss look and feel. Don’t ask me why it looks good in some situations and not in others. I’ve just learned to try a lot of different ideas to capture beauty!

Arched Box Truss – Many times a space will feel better by eliminating the traditional orientation of timber trusses and placing a Box truss at the ridge- or two box trusses spread slightly apart from the roof peak. Creating a big arch or smaller arched webs is a common solution to avoid looking too heavy for some clients taste. Obviously, a big arch at a shallow angle provides no additional strength, but yet everyone calls it an arched box truss. (If it looks like a duck, if it walks like a duck and it quacks like a duck, it must be a duck!)

In the example above, loading constraints for this arched Box truss then would be limited to how big of a span a simple beam could take. Regarding the loading capacity for the other examples, refer to the King, Queen and Scissor truss sections to extrapolate rough load capacity for your project.

Cable Truss – This trust is not so often used, but I wanted to include it for two reasons. 1) It breaks the conceptual mold of what is possible with timber trusses. It also works really well with modern style, with its airy feel and visual surprise. Cables also give a nod to the nautical or a coastal style we have defined in our book, the art of hybrid timber framing. 2) The cables give an unforgettable visual picture of tension loading for how a truss actually works. A cable cannot work in compression, only in tension. Extra strength can be gained by using a longer king post to change the leverage or tension angle of the cable. With or without a king post, this truss is limited by the top chord/rafter capacity, just like the simple truss. Without getting extra beefy with the top chords, this trust tops out at about 30′.

Cruck Truss – So you want a ‘barnominium’ feel? This truss is found in a lot of early timber structures and barns as it is such a simple practical building solution. You might call this a glorified teepee! But it is an example of the brilliantly applied common sense, of early builders. Because it was used so often for barns, a stong style association has been set. Also the presence of the long tall knee braces, really dial up the rustic factor making a ‘barnominium’ feel a natural easy step.

Or stylistically, this truss can also be used to create a hobbit-like look and feel, if the space is kept cozy and the timbers retain a lot of live edge in an organic form. The best looking cruck truss I have seen to date, was featured in the timber frame journal years ago. An Australian timber framer built his own home with a lot of natural curved timbers sawn flat on both sides leaving a lot of rounded live edge. And he had a lot of timber posts, as he used mud and wattle in-fill between the timbers to form the exterior walls. This turned out very warm, whimsical and charming! I suppose I should qualify that – best looking is ultimately in the eyes of the beholder!

The cruck truss without organic edges and a steep roof could work also work well with a chalet or mountain lodge style. This rustic truss has some span capacity limitations. Anything over 30′ will begin to create challenges for tension loading and second floor loading spans.