Truss questions

[Rodmo1]

Hello all,

this is a continuation of my previous pole barn questions thread. Two days ago I started setting trusses. My pole barn package came with little info regarding the proper bracing of these trusses. They are 24' spans set 24" on center. I have them lined up and temporarily braced beautifully. This morning I ran 3 continuous lateral braces on the bottom chord (one exactly in middle and the other two are ran just outside of where the "w" pieces connect with the bottom chord. I believe this should be perfectly sufficient. My main question regards the perm. bracing of the upper parts of the trusses. After speaking to the supplier they recommended running two 2x4's straight through the trusses attached to the inner webbing towards the top. He seemed somewhat uncertain of the exact recommended way. This certainly sounds easy enough to do, however I would think you would need some sort of diagonal bracing to keep them from slouching over. I understand that the roof will take care of most if not all of these stresses when it is installed however it seems after reading online that I should still install these diagonal braces. Wondering what all of your thoughts are?
Question #2
Once all the trusses were set upright I noticed that they generally only touch one of the headers. Some of them have over 1/8" of daylight shining through.. Is this normal? I could easily shim the opening if this is something to be concerned over.

Much appreciative,
Rod M.

 

[Rodmo1]

I failed to add that they are 4/12 pitch

 

[tommu56]

Mine have the loggitudinal ones like yours too.
It also has an angle brace from the top (at the ridge) on the center verticle truss member on the end truss back to the 3rd truss at the bottom of the verticle truss member and nailed in to the center of the verticle trus member on the second truss.
This forms a right triangle to keep the truss top from falling out

tom

 

[Duffster]

IIRC correctly you are having a plywood and shingle roof

The plywood will hold the top of the truss, so no need to woory about it falling out

The angle brace holds the wall line stiff were the gable truss meets the wall

You can brace this two ways, if you have a center upright in the truss you can put it along side that or put one on each of the long webs in the "W"

Most will put it with the bottom on the lateral brace and the top on the gable at the ridge but for a sheathed roof the opposite is better IMO

Probably not an issue with your size building but any truss web member over 8' should have a lateral brace or a T brace

ps Your trusses should have come with detailed drawings and bracing details

 

[tommu56]

Rod
Here is a dyi link and shows some bracing details.

http://www.public.iastate.edu/~mwps_dis/mwps_web/plans/truss_24.pdf

on page 4 called wind bracing mine is from the 1 to the 3 truss in an x shape on both ends
tom

 

[Rodmo1]

Okay if I read this correctly the angle bracing on the ends is only to stiffen up the gable truss. My building has a cross piece that spans the gable truss at the top of the gable end posts. The gable truss is nailed many times into this cross piece tightly anchoring it into the posts. It sounds like the guy at the lumber yard was correct and all I should do is run two lateral braces on the w's in addition to what I already did. (my trusses dont have a vertical center piece).
Another question...anchoring these braces with 16p nails...are these too big (2x4 chords) and actually weakening the members?

 

[Duffster]

Okay if I read this correctly the angle bracing on the ends is only to stiffen up the gable truss. My building has a cross piece that spans the gable truss at the top of the gable end posts. The gable truss is nailed many times into this cross piece tightly anchoring it into the posts. It sounds like the guy at the lumber yard was correct and all I should do is run two lateral braces on the w's in addition to what I already did. (my trusses dont have a vertical center piece).
Another question...anchoring these braces with 16p nails...are these too big (2x4 chords) and actually weakening the members?

You need the angle brace unless the gable end posts reach to the top chord of the truss, even then it would still be reccomended

The 16d's are fine

 

[Gazelle]

You should have a HIB detail sheet showing the recommended bracing. This would be at each end of the building and at every 30' in between, roughly ea. at a 45 degree angles. The bracing should be in the top and bottom chord planes as well as any web members. Additionally, the gable studs should be braced as well. Lastly, each truss has its own bracing requirements whether its for the chord members or for the web bracing, the sealed drawings for each truss design should specify clearly what these are, if any.

 

[MikeD74T]

Rodmo1, Don't rely on your own or the salesman's best guess unless you're willing to take full responsibility for any structural failure. Get a spec sheet from the truss manufacturer specifying the bracing requirements. Trusses are not stand alone elements but are one part of a completed structural system.
Look here Literature at the encylopedia of trusses section, especially the bracing section. Also note that it's very plainly & strongly stated that proper bracing is the responsibility of the builder.
I've erected many acres of trusses, wood-steel- roof- & floor. Bracing is everything & bracing that forms a triangle is essential. MikeD74T

 

[Egon]

Trusses are not stand alone elements but are one part of a completed structural system.

Take note of the above advice and make sure you have the correct vertical and horizontal bracing in place.

Have any of you ever seen the typically large building under construction that has just had the trusses installed. Overnight a wind comes up and the next day the trusses are all laying down in pieces?

 

[Rodmo1]

Thanks Mike for the link. that was the best info yet on trusses. I wanted to add that the lumberyard I spoke to regarding proper bracing was the builder of the trusses. My style of truss is the "fink" pattern. I will definately add angle bracing after reading that material. Although I am not sure how I will span minimum three trusses with a 45 degree on the web member but it will happen.

Rod M.

 

[WVBill]

I wanted to add that the lumberyard I spoke to regarding proper bracing was the builder of the trusses.

Rod - I will echo what the others have said. The truss manufacturer should have supplied you with sealed permanent bracing documentation along with the sealed truss drawings. When I built the studio building for my wife, I had to provide both with the building permit request - and the building inspector looked at the bracing more than he looked at the trusses themselves. It's a truss system.

 

[Duffster]

Thanks Mike for the link. that was the best info yet on trusses. I wanted to add that the lumberyard I spoke to regarding proper bracing was the builder of the trusses. My style of truss is the "fink" pattern. I will definately add angle bracing after reading that material. Although I am not sure how I will span minimum three trusses with a 45 degree on the web member but it will happen.

Rod M.

Rod. you don't need to worry about it being exactly 45*

If you angle brace back to the third truss would be sufficient

 

[Rodmo1]

I am still waiting on the official paperwork for the trusses so I thought I would post a couple pics of the progress so far.

 

[Duffster]

Looks good, very sturdy

How come your not putting a metal roof on it?

 

[MikeD74T]

Rodmo1, If you liked the last link you'll love this one. http://mainelytrusses.com/pdf/wtca/bcsi_guidebook.pdf No more waiting, it has more truss information than anything I've seen before. Go to their products page for even more info. MikeD74T

 

[Rodmo1]

Thanks Duff and Mike,

I am not putting a metal roof on because I want it to match my house and other outbuilding. In hindsight I probably should have used metal roofing to qualify for the tax credits. It will get dimensional shingles and 4" clapboard siding. Picturing it in my head it looks very nice but I will have to wait and see what reality is. Got very concerned yesterday morning when leaving for work I noticed a very visible bow on the gable end truss. After worrying about it all day I came home and pulled a string only to find out one pole is just 1/2" off 9' up. Amazing how bad 1/2" out of plane can look to the builder/owner and probably no one else. thanks for the sturdy comment Duffster...That was my main goal...I do not want to worry about this building come any foul weather. I put 45* bracing on the long walls and will probably put some on the gable walls as well. Although I think sheathing alone will brace it enough. With all the surrounding trees there is not much ground level wind here.
Anyhow I will post more pics in a couple days when the roof should be done.

Thanks all for the help
Rod M.

 

[yooperdave]

The truss designer will specify what needs to be braced permanently and where.

There should be shop drawings which specifies this.

Compression members not braced as designed may buckle causing structural problems.

Bracing is one of the cheapest ways of stabilizing most structural members.

The roof deck is a diaphragm which will brace the top chord.

Many different load cases are used in the design to determine stress reversals - tension members going into compression which could buckle.

This is not a guessing game - find out from who sold you the trusses to see the shop drawings. Proper bracing is routinely omitted or screwed up by many contractors.

Good Luck

Yooper Dave

 

[Duffster]

The truss designer will specify what needs to be braced permanently and where.

There should be shop drawings which specifies this.

Compression members not braced as designed may buckle causing structural problems.

Bracing is one of the cheapest ways of stabilizing most structural members.

The roof deck is a diaphragm which will brace the top chord.

Many different load cases are used in the design to determine stress reversals - tension members going into compression which could buckle.

This is not a guessing game - find out from who sold you the trusses to see the shop drawings. Proper bracing is routinely omitted or screwed up by many contractors.

Good Luck

Yooper Dave

I agree

But they are just a 24' common, so not real complicated

 

[ldwain]

The industry documents for truss bracing are found at this website: Building Component Safety Information. The BCSI booklet describes the required bracing for truss systems. Specifically, the B10 document describes bracing for post frame buildings. And yes, diagonal bracing is ALWAYS required in truss systems even when the end gable is attached directly to the posts. The diagonals are placed a intervals along the length of the building to transfer the lateral forces that accumulate in the continuous lateral restraints to the roof sheathing and/or ceiling (if supplied).