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toyota_mdt_tech
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# Posted: 10 Feb 2021 10:38pm - Edited by: toyota_mdt_tech
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OK, this is for the engineering types in here, (ICC etc) and everyone else too, please chime in.
I built the frame work for a log park shelter, 10X16 with 2 feet of overhang all around. Headed back in spring to sheet it and install metal roofing. (man are lumber prices high now)
Pricing lumber today, 2X6X8 is $11.75 while a 4X4X8 is $12.25 (50 cents difference). I am using dimensional lumber to frame the roof. Obviously, the sheeting is much easier to land on a 3.5" wide serface vs the 1.5" surface and the squared rafters would look better on a log structure vs the 2X6. The run will span 6 feet. I am spacing them at 24" OC
Trying to anchor a 2X6 to logs, its not like I can find a Simpson strapping, but I can easily screw down a 4X4 with a timberlock. It would also increase surface area where the timbers meet the round logs with less grinding away for a flat spot and some grinding will also be done to keep rafter tails in alignment/even for the fascia too. I will sheet it all with 19/32 plywood with H clips.
OK, let me have it. 
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ICC
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# Posted: 10 Feb 2021 11:59pm
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Snow load?
DougFir, HemFir, SPF, or???
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snobdds
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# Posted: 11 Feb 2021 01:13am
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4x4's don't have the strength as a 2x6, but since it's a timber frame...it just needs to support the roof and associated loads. I wouldn't use pressure treated as they're even weaker.
I assume your putting these on top of the roof logs?
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Brettny
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# Posted: 11 Feb 2021 06:11am
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Beautiful frame toyota. It would be a shame to be in that beautiful building a look up and see kiln dried lumber from lowes. Have you thought about useing roughcut? Are you going to use metal roofing? If so I wouldnt use plywood.
I guess this all depends on its final use. What's a park shelter? A car port?
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toyota_mdt_tech
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# Posted: 11 Feb 2021 07:57am - Edited by: toyota_mdt_tech
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Quoting: ICC Snow load? DougFir, HemFir, SPF, or???
OK, it will all be douglas fir, I specifically look for that and its easy to find over in that Home Depot.
I am going by memory, but when doing my cabin, I remember 90 on the snow load. I also used 2X6 on the cabin, but its at 16" OC and the span was longer
None of the wood will be pressure treated. I know 2X6 will be lighter than the 4X4 also.
Brett, the area is dry over there and I will not be using the standing seam, but the ventilated "delta ribbed" stuff over 30# felt. The mfg list this method in their instructions. Now a standing seam with no vent ribs, I'd use a membrane under it.
I know dimensional lumber isnt ideal, log rafters would be perfect. But time is a factor. It will all be painted in my forest service brown too.
A park type shelter is just a covered area where people gather, it will have a large table in the middle, I will install log rails up at the 36" and it will also aid in strengthening it. Over there, its more to keep the sun off vs rain. Right now, I just set up an EZ up over the picnic table off the cabin porch. I aligned it to be square off the porch, picture of it in relation to the cabin.
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Brettny
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# Posted: 11 Feb 2021 08:05am
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We could call that a pavilion here. Since it's open underneath cant you just use rafters and perlins?
I think the rough cut lumber look would fit better with the look of the rest of the structure. You could even have one live edge left on the perlins so really add to the natural/log look.
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toyota_mdt_tech
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# Posted: 11 Feb 2021 08:34am - Edited by: toyota_mdt_tech
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Brett, rafters and purlins is another way the roof mfg list, I would be worried about snow, branches hitting it, snow clumps etc. So the underlayment of plywood is to just make it resistant to damage. I will be cutting back the forest around it for more fire protection also.
But you do have me thinking on it now.
Quoting: snobdds I assume your putting these on top of the roof logs?
Yes
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Brettny
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# Posted: 11 Feb 2021 09:14am
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Rafters are needed in any plywood or perlin method. At least price out the cost of boards over plywood. Plywood is highly priced now.
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toyota_mdt_tech
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# Posted: 11 Feb 2021 10:20am - Edited by: toyota_mdt_tech
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Quoting: Brettny Plywood is highly priced now
I have, for 19/32, its $42 per sheet ($40 for 15/32). I'm looking at close to $500 in plywood. If lumber was high, I was going to hold off, but toomuch planning into this, coordinating with free work crew (lots of good pals, free labor, son in law) so its on. I hate to think what the metal roof is going to cost. It was over $1200 for my container roof.
I'm thinking the plywood would tighten it up the structure. I worry about high winds, we get those, rare, but they do show up. Main reason I am adding logs between uprights too. I will add more bracing to ridge log and wall logs at the ends, just want to see where they get trimmed first.
Locking down 2X6 to logs, how about drilling small pilot hole and winding in a timber lock screw?
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Brettny
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# Posted: 11 Feb 2021 10:31am
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Was the metal roof the big box store price? I have found local places and even one company that bends metal pannels on there site is cheaper than big box stores.
As for stopping the building from racking it can be done with pine boards too.
Generally screws driven with an impact driver will sink the head very well.
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snobdds
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# Posted: 11 Feb 2021 10:36am - Edited by: snobdds
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I think sheeting the roof makes for a far stronger roof in snow country. Metal on purlins is just asking for trouble with snow loads. I have seen more than a few roofs with purlins where the snow has deformed the metal between the purlins.
I think your plan is fine with a timber frame. If you want to add some rustic features to the 4x4, just get a chain with a bolt at the end and bash the wood to create some texture.
I'm glad to see cost is not the primary driver of this endeavor, but functionality. Far too often cost concerns get in the way of making something of quality. With wood prices where they're at now, were going to see a lot more corners cut and interesting designs to save a buck. I think high lumber prices are going to be around for awhile, unfortunately.
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Brettny
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# Posted: 11 Feb 2021 12:15pm
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No ones saying to cut corners and at $31 a sheet of 7/16 osb I would be strongly looking at the price difference in useing rough cut pine boards. You dont need to space them every 2'. They dont even need a space.
Pine 1x6x8' boards from a mill are $0.80 per square foot. 7/16 osb is about $1. At least shop around and I dont think thinking out of the box a bit when building materials are so over valued is a bad thing.
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ICC
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# Posted: 11 Feb 2021 12:24pm - Edited by: ICC
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Several comments.
A length of 4x4 has about 40% less resistance to bending than a 2x6 of the same species, grade, and length. I calculated that using the timbertoolbox beam calculator and comparing the amount of deflection for a random evenly distributed load.
I then used the AWC rafter span calculator and selected the following criteria: 2x6, DF #2, 24"OC, deflection of L/240, dry and not incised. Changing the snow load I found that with a snow load of 130 PSF that 2x6 would be rated for a span of 5'3".
Your 10 foot wide shelter should have a span of about 5 feet, actually a little less if the 10 foot dimension given is to the outside of the structure.
If we reduce that snow load by about 40% to compensate for the loss in bending resistance of the 4x4 we end up with about 80 PSF snow load.
I'd say that is close enough and the planned 4x4's will be okay for a picnic shelter. IF one wanted to build it a little stronger think about changing the rafter spacing to 19." OC. That would need two more rafter pairs but would be able to carry more load. The AWC calculator has that spacing as a selection.
Re the comment about PT wood not being as strong as non-treated... Yes that is true, but the difference is really nothing to worry about. Having a look at the tables published by the Southern Pine Council we can see that for an example of a visually graded floor joist of 2x6, #2 post June/2013 grade, L/360 and 16"OC the Pressure Treated version can safely span 9'0" wheres the non-treated version can safely span 9'4". Not a significant difference.
IF the location where the lumber is used would be called a wet service condition, then the span of any lumber needs to be reduced. That would be deck joists that are open to weather. The rafters under a weather resistant roof are called a dry location. If you look at the AWC calculator you will find there is a field to select wet or dry.
PT wood that is wet from the treatment plant is not fully rated until it dries out. Once it air dries to the same moisture content as non-treated lumber there is only that small difference in resistance to bending.
One other thing that reduces the load-carrying ability of any lumber is if the items in question are incised. The surface looks like a bicycle chain sprocket has been run up and down the length. Some species, like DF, need to be incised if it is to be pressure teated. That reduces strength because fibers are cut. The AWC calculator has a selection for incised, Yes/No.
I would definitely sheath the framing with plywood or some other suitable sheet material. The reasons were mentioned by toyota_mdt_tech; great increase in racking strength and the decking greatly reduces the chances of damage from falling or windblown debris or heavy snow loads. I too have seen metal roofing on a purlin only shed deformed by snow loads.
Re: rough sawn timbers. I do sometimes like the appearance but mostly do not. Plus that surface soaks up paint and stain like crazy.
One Question...
Are the roofing screws going to be visually detracting where they will be penetrating the roof deck sheathing? I have a similar shelter and ended up installing pine T&G on the underside of the roof structure for two reasons. The protrusion made painting by brush slow and messy and I did not want to spray. The protruding screws were not aesthetically pleasing to my eye. So I ended up applying T&G pine and clear coating it. No stain at all in order to keep it lighter colored up there. That seems to make it less dark under the shelter roof.
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toyota_mdt_tech
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# Posted: 11 Feb 2021 01:22pm - Edited by: toyota_mdt_tech
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ICC, Brett, and snobdds, thanks for the advice. Looks like I am overbuilding it, good, I am not an engineer, so I tend to error on the side of HD (overbuild) OK, great info, I will look at the 4X4's, if they have enough on hand, I will use it, otherwise, the 2X6. ICC, the 10 foot width is on the center of the uprights, the top wall log is centered over that. I will use 19/32 or closer to 5/8 plywood (measure in 32nd now vs 1/8ths) and no OSB. The thicker wood is more desirable for those roofing screws. They will protrude through. A pro roofer I knew said the short screw with the taper tip doesn't have much surface area to hold with the pointed tip flush, He liked the fatter screws and protrude through. My cabin is done that way and you dont even notice it after it was painted the dark brown.
Plywood sheeting will make coverage go faster and I wont have the toggling between each plank. I will use probably 2 H clips between each joint between rafters. Snow load and deformation is a concern. So it looks like I will go plywood, heavy felt and see if they have enough 4X4's for me, I will go that route.
The metal I get is from Metal Sales, its not box store, I especial order it from a building supply, I give them the sheet length, I get the facsia flange, gable flange and I get the foram blocks for the underside and top so insects don't nest in the vent ribs. It sticks onto it, underside at the bottom and topside at the top and ridge cap based on my roof pitch and give them the length. I get the Delta Rib in 24" wide in "Sierra Green". This is the NW section of the site.
I built a scale model of it, ie 1" = 1 foot using dowels, so its easy to determine the rafter length while maintaining overhang and high enough to not hit your head on it with the model. So I will run rafters wild, measure overhang, snap line, trim tails, add 2X6 fascia and I want the metal to overhang 1.5" off that. So be a little less than the full 8 feet for the roofing metal sheets and I will have very little plywood waste too.
This is the stuff.
Sierra Green color (#20)
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ICC
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# Posted: 11 Feb 2021 03:13pm
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Quoting: toyota_mdt_tech A pro roofer I knew said the short screw with the taper tip doesn't have much surface area to hold with the pointed tip flush,
I think you will find that the metal roofing manufacturers specify the points must protrude by a certain amount.
Quoting: toyota_mdt_tech The metal I get is from Metal Sales, its not box store.....
Yep, that is the way to go. Measure and get the exact lengths needed and no need to splice joints, just one piece. I have some very long lengths used on the house here. Also some very short pieces used to skirt a couple of raised structures. Much better to have the supplier cut the sheets before the panels have the ridges rolled.
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skootamattaschmidty
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# Posted: 11 Feb 2021 03:14pm
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Just another idea...to keep it rustic, have you thought of using logs for the rafters as well? If you cut a few more trees on your property and used logs then the cost is free. When I built my log sauna I used logs for the rafters then sheeted it with 1x5 rough pine boards, then metal over that. It really ties in nicely with the log look. Just another option.
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skootamattaschmidty
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# Posted: 11 Feb 2021 03:14pm
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And btw, I love the structure you have made thus far! That's fantastic!
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toyota_mdt_tech
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# Posted: 11 Feb 2021 06:38pm - Edited by: toyota_mdt_tech
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Quoting: skootamattaschmidty And btw, I love the structure you have made thus far! That's fantastic!
Thanks skoot. I am particular and fussy on anything I do. As for the log rafters, that would of been ideal. But this whole deal came on so fast. I had some beetle kills, still standing. I dropped them and skidded them to a landing. After a year of setting, grab a flooring scraper, (log home builders call them bardk spuds) and that bark came off slick as a whistle in a few minutes per log. So now I have these nice peeled logs and the wheels started to turn as to what to do with them. Keeping with my park theme and wanting to do away with the table under the EZ up, it was settled.
Collecting enough logs of the right diameter would take a while and building with logs is slower then dimensional lumber. So its Home Depot for the rest.
I have given it the name "The Teddy Roosevelt Memorial Shelter" as Teddy was instrumental in the national parks.
I have 4 more beetle kills standing I marked last fall (3 pink ribbons) for felling and skidding out in May, there may be more by now. I will use these for rails. They are about the size of the ridge log or bigger. Tall and straight. Will use it for the perimeter rails
Custom made sign for shelter.
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snobdds
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# Posted: 11 Feb 2021 09:45pm
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Its neat the theme you got going. The us Forrest service has a long and storied past.
But to be honest, I have really noticed a decrease presence over the last ten years in the Forrest. The signage is in horrible shape. The ditches on the roads are full of trees and let water run on the roads. The road to my place is so rough, water erosion has exposed boulders...its crazy.
It just seems like the Forrest management is lacking, so to see some new life in a place is refreshing.
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ICC
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# Posted: 11 Feb 2021 10:25pm - Edited by: ICC
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What the FS is lacking a lot of is money. The people who decide on the FS budget also need to decide whether or not a tree has any value if it is not cut down. And that is about as far as I will go on that topic right now.
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snobdds
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# Posted: 12 Feb 2021 12:08am - Edited by: snobdds
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There's hope, but fires are crazy expensive...
Signed into law summer of 2020.
"The Great American Outdoors Act responds to the growing $5 billion backlog of deferred maintenance on national forest and grasslands, which includes $3.7 billion for roads and bridges and $1.5 billion for visitor centers, campgrounds and other facilities. The Forest Service currently administers more than 370,000 miles of roads, 13,400 bridges, 159,000 miles of trails, 1,700 dams and reservoirs, 1,500 communications sites, 27,000 recreation sites, and 40,000 facilities of other types. In addition to helping address deferred maintenance for these critical facilities and infrastructure, the Great American Outdoors Act will help the Forest Service to continue supporting rural economies and communities in and around national forests and grasslands across the country."
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