Pole Barn Addition

[75Shark]

I have officially ran out of space in my 32X48 pole barn. I am thinking about adding a 12X40 addition off one side of the building for cold storage (tractor, implements, kids bikes, etc.). The current building has a 12 foot ceiling, with 4/12 pitch roof. Laying out the poles is pretty straight forward, but I am having a hard time determining the best way to add the new rafters to the existing structure. Do I attach them to the existing header?

I have a quote to have this addition constructed, but was shocked by the price (about half what the original building cost). Other than adding the new rafters, I am confidant I can do the build myself...so I am looking for advice from some experts who have added lean-to's or additions on their buildings.

My concept sketch is attached. Obviously, this only depicts part of the framing, but you can see the addition on the right side of the main structure. My main question is how to attach the rafters to the existing building.

Thanks

 

[matt_i]

You can of course set the new rafters on the existing header, this is probably very common. It would be super high end to add new support posts, and new foundation for the new loads...but this seems excessive. Medium-end, I would look into ways to beef up the existing header, sistering timbers, adding mechanical fasteners, like more nails, GRK screws, or integrate machine bolts. Low end, just peel back the roofing enough to expose the framing and nail up the new rafters.

Detailing the roofing at the new interface will be the most critical part in my estimation.

 

[cj7jeep81]

We did basically the same thing at my dad's shop last year (only not as big). In his building, the trusses were on 2' centers, and we put rafters on 16" centers. We just cut them a little long to go back over the existing header, and used hurricane clips to attach them. In some places, I think we had to fudge it a bit and placed it beside the existing truss, so it wasn't exactly 16" on center.

 

[Vegaman_Dan]

Sister in another header with bolts and attach your rafters to that. It's not that big of a span to cause any real load issues.

I'd advise adding some blocks between the rafters to keep them from racking or twisting. Beyond that, looks pretty straight forward. Will the side be sheathed? That will add a lot of strength, and give you some storage options for the inside of the wall.

Might be worth putting a concrete pad in there, or at least gravel to help with drainage. Heck, I'd be tempted to put in a small pad to move your air compressor to the outside and gain more shop space as a result.

 

[75Shark]

Sister in another header with bolts and attach your rafters to that. It's not that big of a span to cause any real load issues.

I'd advise adding some blocks between the rafters to keep them from racking or twisting. Beyond that, looks pretty straight forward. Will the side be sheathed? That will add a lot of strength, and give you some storage options for the inside of the wall.

Might be worth putting a concrete pad in there, or at least gravel to help with drainage. Heck, I'd be tempted to put in a small pad to move your air compressor to the outside and gain more shop space as a result.

Forgive my ignorance...are you suggesting to add another header (2x12 like existing) to the outside of the sheeting? The building is plywood and vinyl siding. What is the best method of attaching the new rafters to the new "sistered" header?

 

[bullnerd]

I'm with Dan. Doesn't have to be a 12" though. I would use whatever your rafters are.

You could probably get away with just adding hurricane ties to the existing header, but I am not qualified to make that decision for you. Your in serious snow load country ,So a header is probably the way to go and still easy to do.

You have to decide how to do the siding, without pics it would be hard for us to tell you exactly what to do. Cut the siding back/down, add the little siding trim piece(J channel) and bolt the header on. Hurricane ties on both ends of the rafters.

 

[Sureshot]

I was looking to add the exact same thing to my shop. The plan was to cut the exterior tin down to what would be the new ceiling height and use a mono truss off the existing poles that were 6' centered.

One of my past employees worked for a major pole building company and told me the vast majority of warranty work they did was the roof joint on projects like this but when the roof angle changed so I would stick with your plan of 4/12 for the addition. I ended up building with the peak at 90 to the original on the opposite side for various reasons.

 

[lakeroadster]

If you can live with the height difference have you considered adding the new structure below the existing overhang? You leave the entire existing roof and headers alone, and add the new structure below.

 

[75Shark]

Not sure if I can live with the height difference... I am pretty limited on distance to property line on that side of the building, and am trying to get the widest addition I can without needing a variance. Ultimately, I would like to use the existing header (or beef it up if need be). Thanks for all the input. I think this is something I can do on my own for considerably less than what was quoted to me.

 

[GYOGI65]

I did the exact same thing on mine remover fascia board and slid 2x8 rafters along side existing trusses matched existing pitch 6/12 and installed matching metal roofing been 14 years no issues other than now building 20 x26 addition on the back with ceiling height enough for a lift never big enough

 

[NUTTSGT]

Personally and especially with the snow loads you get up there in Rochester, New York, I'd rather have the new rafters sitting on the header than to have them nailed to the face of them.

 

[bullnerd]

I agree with the last two posts, but he hasn't mentioned what the trusses are made out of? They may be 2x4? They look way smaller than his new rafters in the sketch.

 

[NUTTSGT]

I agree with the last two posts, but he hasn't mentioned what the trusses are made out of? They may be 2x4? They look way smaller than his new rafters in the sketch.

Good point.

If that's the case (you never know till you actually see it or a picture) I'd consider doing both sitting the rafter on the header and sistering up another header up to the old one. I'd stagger the new one down from the old one so you could still get the full height of the new rafter (2x6-2x8) sitting on it. Something like a double bird's mouth.

 

[52wrench]

What size is the existing top truss chord? Cut the siding and sheeting down and install another header below the existing outside header then slide your new rafters on top sistered to the existing chords. If the top chord is too small to use the same size as a rafter for the new span on same c to c then double up new rafters. You will have to get it inspected so probably PE stamp req'd on design.

 

[lakeroadster]

So your trusses sit on a header? Interesting. Most pole barns have the trusses sitting on top of the posts? Got any photo's you could post up for us?

 

[75Shark]

What size is the existing top truss chord? Cut the siding and sheeting down and install another header below the existing outside header then slide your new rafters on top sistered to the existing chords. If the top chord is too small to use the same size as a rafter for the new span on same c to c then double up new rafters. You will have to get it inspected so probably PE stamp req'd on design.

Existing trusses are 2x4's. Are you suggesting something like this?

So your trusses sit on a header? Interesting. Most pole barns have the trusses sitting on top of the posts? Got any photo's you could post up for us?

The trusses sit directly on the header(s).

 

[lakeroadster]

Thanks for the photo and cut-away model. Interesting.. kind of a hybrid design.

You aren't getting much strength out of that attachment since you are cutting so much of the rafter away.

I'd use a Simpson Strong Tie Rafter Hangers and Structural Screws. These go up fast and are very strong. http://www.strongtie.com/ftp/catalogs/c-c-2015/c-c-2015-p092-093.pdf

Part of your cost is going to be getting an Engineer to stamp your design.... got one lined up?

 

[52wrench]

No, if the top chord was 2x6 then you could use 2x6 for the rafters and double up but that won't work with 2x4. To do what you want nail a second header to the posts directly below the existing header, but then you'll need another 2x bolted to the headers so the rafters bear on it, you can't birdmouth your rafter that much w/o another bearing board supporting the rafters.

 

[52wrench]

Or use rafter tie as as Lake suggested. In any event you'll need a stamp to get it passed.

 

[NUTTSGT]

So your trusses sit on a header? Interesting. Most pole barns have the trusses sitting on top of the posts? Got any photo's you could post up for us?

Since the OP has his trusses set 24"OC and sheathed with plywood, I wouldn't be surprised if he didn't have his roof shingled rather than metal.

Existing trusses are 2x4's. Are you suggesting something like this?

The trusses sit directly on the header(s).

Going with trusses every 24" and plywood for the exterior walls, I'd venture to say the OP put some serious money in this building with the intent to make it nice.

Is the roof shingled or did you builder do that for the serious snow loads ?

 

[NUTTSGT]

Existing trusses are 2x4's. Are you suggesting something like this?

I would do a rafter similar to that but put a second bird's mouth just below the one that is there. The lower birds mouth will sit on the "sistered" header that I mentioned above.

No, if the top chord was 2x6 then you could use 2x6 for the rafters and double up but that won't work with 2x4. To do what you want nail a second header to the posts directly below the existing header, but then you'll need another 2x bolted to the headers so the rafters bear on it, you can't birdmouth your rafter that much w/o another bearing board supporting the rafters.

Basically what I was alluding too above in post 13.


A little exaggerated and my "paint" skills may not be the best but the double bird's mouth in the attachment.

 

[bullnerd]

No, do not notch the rafters like that. You effectively reduce their size/strength to the thinnest cross section.

Is the building sided yet? I didn't see it.

Either add a small header to the side of the existing one or just use the strongtie/hurricane brackets and go right to the existing one. Line up the top of the new rafters with the existing ones if you want the roof sheathing to line up.

I put an addition on my house and part of the roof ended up being a lean to type of deal. The inspector said he wasn't worried about snow load, but he was worried about wind lifting it since it was open underneath. So I added the brackets and he said that's good.

 

[ezover]

Forgive my ignorance...are you suggesting to add another header (2x12 like existing) to the outside of the sheeting? The building is plywood and vinyl siding. What is the best method of attaching the new rafters to the new "sistered" header?

that is what I did. I used lag screws to attach new header. sorry the pictures do not show what you are looking for but they might give you some ideal of what I did. I did not make a over hang on the leanto, as it is under 6 foot and I did not want to bang my head on it when I walked around the comer also it saved some work by making it flush.

and yes it went right over the metal siding. then i used hangers? to attach the new rafters to the new header. I thought about doing it like post #21 above but it was a lot more work to only gain a few inches of height.

 

[52wrench]

"and yes it went right over the metal siding. then i used hangers? to attach the new rafters to the new header."
Did the inspector pass that or?

 

[ezover]

"and yes it went right over the metal siding. then i used hangers? to attach the new rafters to the new header."
Did the inspector pass that or?

never had it inspected. is it code no clue, I used the hangers the folks at home depot told me to use for roofing.

 

[ezover]

I think this is something I can do on my own for considerably less than what was quoted to me.

my barn is 32x48 also I believe I had about 2200.00 in material cost.

 

[75Shark]

Sorry...I should have mentioned that the existing building is vinyl sided and shingled to match the house. The addition will also be sided and shingled (hoping to reuse the siding that is currently on the wall that I want to add on to.

I plan to call the town inspector today to see if he can advise on what he deems acceptable (strongties or additional header/birdsmouth).

 

[NUTTSGT]

Be careful pulling that siding off in the cold weather. I'm sure you know it gets brittle. You might want to only pull off the siding you need to to get the addition built. Once it's closed in, put some heat in there, aka space heater, to warm it up and then pull it off.

 

[bullnerd]

"I plan to call the town inspector today to see if he can advise on what he deems acceptable (strongties or additional header/birdsmouth). "

Good idea.

Good call on the cold vinyl!

 

[75Shark]

Town inspector not available yesterday...will keep trying. I would not be building in this weather, I would wait until spring/summer when it warms up to avoid the cold vinyl issues.

Thanks