Bracing an old shed

[Maximus]

Before things go all leany, we would like to reinforce the main post and beam joints on this old shed.  Adding longer 3-1/2"x3-1/2" knee braces with 6" timberloc screws was our baseline idea.  I do not plan on cutting into the existing posts and beams at all, not even to predrill the holes (though I will predrill through-holes in the new knee braces).

We like the look of this building and want to preserve it kinda unspoiled.  The bright new braces will look extremely out of place for a year or three, but we expect they will eventually pale to a natural gray like the rest of the shed.

Anyone done this and learned some useful "don't ever..." lessons?  We will very happily throw money at this if there is a better way.  It's a pretty simple building though, and we thought it best to keep it that way.  The existing structure is all done with nails.

[doc henderson]

Off the bat, I would plan to put that brace back, but also extend another in the truss so that the up pressure on the bottom cord is supported.  so, from the upper end of the brace to the intersection of the webbing on the top cord in the truss.

[doc henderson]

i tried to blow up the image, but it looks like there is no top cord, just tied into a purlin or maybe a board (rafter?).  Might lay a 2x along the top and fasten to each member along the way, top to bottom, to make a truss so the brace transfers all the forces into a triangular structure.

[Maximus]

i tried to blow up the image, but it looks like there is no top cord, just tied into a purlin or maybe a board (rafter?).  Might lay a 2x along the top and fasten to each member along the way, top to bottom, to make a truss so the brace transfers all the forces into a triangular structure.

Darn you Doc, always making me learn new things!    

I have to look up a few of those terms and see what they all mean.  Thank you for the ideas!

Ref. your first response, we have not removed anything.

[doc henderson]

sorry, I did not think you had, but were making a new one, and that is what I meant by put it back.  good luck.  maybe some of the construction gurus will weigh in. @Don P (could not get it to highlight)

@Jim_Rogers 

[beenthere]

Any of the braces loose now? (I looked and looked for a brace that was missing, but then read further to learn that none were.    )

Looks pretty-well braced from the small photo shown.

[Maximus]

Nope, all the braces are still in place.  It's old though, and the braces are surprisingly thin.  In one sense, it's an engineering marvel.  Still, I worry about it every time I look at it.  For all the wind and rain and humidity and moss and fungus and beetles here in the PNW, I just want to try the easy stuff to keep her standing for as long as possible.

Our neighbor (ironically, the dude who built the shed; he just recently passed away), clearcut his neighboring lot several years ago, so now we get high winds slamming directly into her side pretty much all winter.  I scraped 3"+ of moss/debris off the cedar roof a couple years ago, so now she leaks like crazy.  We're putting a new metal roof on this spring.

With the saw mill and plenty of trees/lumber, I hate to just stand by and do nothing if there's something useful we can do to preserve her.

It may be the best thing I can do is knock her down, burn the carcass, and rebuild.  It is the absolute finest location on the entire 10 acre lot, so the thought has crossed our minds.

[rusticretreater]

I'm with Doc on that the roof needs to have some triangular bracing in it. The roof presses on the rafters, the rafters press on the triangular truss.  The more pressure, the more sturdy the truss becomes. Right now, the rafter/diagonal brace joint carries the pressure of that entire section of the roof.  That joint fails and you will have a roof collapse.

Don't worry about the appearance, worry about making it sturdy and long lasting.  If you are taking the roof off, that is the perfect time to upgrade the frame.  Look up some roof trusses online.  There are a ton of different designs.

[doc henderson]

Here is what you have.  you need all the weight/stress (wind/snow) from the roof to transfer all the way to ground.



the center half of the roof is triangulated but it all goes to the center of the strap tie or bottom cord of a truss.  the strength of the wood is all that is holding it.  

[doc henderson]

It might be helpful to shott a pic up from under the "truss".  when I study and try to trace where all the braces go, it appears to create a pyramid, and not just triangles.  Not sure if you can see my drawing on the picture of a picture of a picture.  

[doc henderson]

looks like the center brace goes out to rafter # 2?  and the bottom cord and triangular braces go up to rafter # 3?  counting the facia board as rafter #1.

[Maximus]

Wow, gentlemen, thanks so much for the analyses!

(I'm trying to invert the photos)

Please see better, more detailed photos below of the truss/rafter architecture.

Doc, I've always looked at that king post hanging over the center of that floating beam, thinking, wow, dude's a genius!  How did this not blow down or collapse?  He did something right, so I want to give him his due.  (Someone will similarly be looking at our stuff, soon enough.)

Mr. Retreater, I'm definitely not worried about appearance over structure.  I'm happy to make useful upgrades.  It'll be fun, especially if I understand what I'm doing!

Doc, your picture with the knee brace extending to the peak, bisected by another bracing post normal to the rafter is quite inspiring.  I don't know that I've ever seen that before, but now that you've drawn it, I can't unsee it.  That looks brilliant!

[doc henderson]

Well, those pics are great, and I am now understanding.  these are log trusses, and I now think, replacing the existing brace, and adding one from there (on the top of the bottom cord) up to the peak will transfer weight to the ground.  all the rafters between the trusses are carried by the trusses.  That is a neat barn.  

[Maximus]

Thinking back, I seem to remember that the king truss design was based on transferring the vertical post's load back up to the rafter via the 2 diagonal posts.

No?

[doc henderson]

Well now iI must correct myself.  I saw that first pic about 3 different ways.  the new pics are great.  I would add a member that basically extends the knee brace straight up to the intersection of the top cord and the angled member.  I am not sure of the span.  If you tell me thing is 40 years old, well than it may not need anything as it has passed the test of time.  the first pic is small and straight on, and I did not see the brace to the king stud.  I would consider adding a little stub where those two intersect the bottom cord and go to the top cord in a like angle to the other two.  hard to put into words. 

[doc henderson]

I think so, but if the bottom sags, then the whole thing can.  the triangles help but if self-sufficient the bottom cord only keeps the walls from spreading.  I would still like seeing the new post in the truss going to the brace and to the posts and to the ground.

[doc henderson]

[rusticretreater]

Ah, the first picture is kind of an optical illusion making the king post look nearer than the braces.  A few additional braces, either vertical or diagonal as doc suggested would be a great upgrade. Look up a Howe roof truss which is similar to what Doc describes.  

[Maximus]

In case it matters, I'm not worried about a roof collapse.  As Doc noted, the structure has passed the test of time in that respect.  We have no snow-load issues here on the island.

The failure mode I'm trying to interdict is leaning due to persistent winter winds from the side (left side, as one views the pictures).

I understand a truss upgrade along the lines suggested by Doc would also prevent a leaning problem, but it is a bit more involved than I had planned.  I think the roof is solid and not in jeopardy of collapsing, I just want to reinforce the structure against a wind-induced lean.

[doc henderson]

I agree it passes.  how old do you think it is?  I will change/clarify.  I would add a log that basically extends the knee brace up to the top cord at the junction of the web or strut connection.  almost a straight line from the knee brace.  I think that will stiffen things from top to bottom.  If that makes any sense.  I also wound not reinvent the whole thing.  The side building will help brace against the wind as well.  nice structure.  

[doc henderson]

It feels visually that the center group of triangles are close together leaving a longer span of single logs to the outside.  I had trouble with rotation as well.  If I click on your image, it is enlarged and upright.     Welcome back and glad you are ok.

[doc henderson]

If you do nothing, I enjoyed thinking about it!   What is the height?

[doc henderson]

more perspective.

https://forestryforum.com/gallery/albums/userpics/73737/IMG_5031.jpeg

https://forestryforum.com/gallery/albums/userpics/73737/IMG_5030.jpeg

are there other structures similar in the area.  Maybe an old guy with old school knowledge.  a real gem.  log poles sourced on the Island?

[Maximus]

Yeah, it has been fun to think about!  I was being naive, thinking it was as conceptually simple as just upgrading the knee braces.  But as you gentlemen have pointed out, I have to think of it as a structure with loads running from the 14' peak all the way to the ground. 

In light of the thought experiments we've been through here, I'm going to sit back and stare at it awhile.  It is interesting to note that the structure could lean w/o altering the truss geometry at all, so my first inclination is to not mess with the elegance of those existing minimalist trusses.  But if I do upgrade the knee braces somehow, I'll keep in mind your observations about top-to-bottom load transference.

My leaning-phobia comes from the condition of the posts at their base.  Dude dug them in and wrapped them with garbage bags.  Amazingly, they're still fine, but at my age, I'm reevaluating all systems around this place that look like they may be on a glide slope for failure just about the time I become too old to enjoy fixing them.

When we first bought this place, we chatted by phone with the gentleman who built the shed.  (He lived in WY and simply maintained the adjoining 20 ac. lot as an investment.)  "I built that thing with an ax and a bottle of water as a level," he said.  All the wood is from this lot.  He owned the property from 1986-2002, so the shed was likely built sometime around 1990.  He also built a nice log cabin and wood shed (the latter being a smaller twin of the shed).  They're all simply wonderful structures, but for city boys like me, there's a learning curve to maintaining them.

[beenthere]

I would do nothing but get the waterproof roofing over it, unless there are already joints that have decay from the leaking roof structure and are compromised.