## 20x34 2-story universal in upstate NY

Started by NathanS, May 13, 2016, 11:04:09 AM

0 Members and 1 Guest are viewing this topic.

#### NathanS

#175
Thank you Chugiak. Yes it is unreal we built this place. And I do spend a lot of time just staring not believing it.

Step back to the calculations we've been doing for the shed roof. I made a little bit of a boo boo. My 2x10 stock is southern yellow pine. I looked up on the NDS sheet... it's got like double the rating of SPF.. and all other species. It's got it's own section.

Fb = 1850
Fv = 175
E = 1.7m

I ran some numbers, not in front of me right now, but I think the 2x10 SYP @ 16" is stronger than the 2x12 SPF @ 16". What! It looks like it passes the bomb falling on it test without needing to double rafters.

This is a whole new can of worms, and I started to plug things into Don's calculator.. but we are going to go try and finish this dang roof today so it's got to wait till tonight. But, why are the NDS #s so much higher for SYP, but the span tables in the code not really any different, and sometimes lower than other species?

I remember reading (I think from a post Don made here once) that SYP got derated a few years ago. The NDS tables are from 2005. That probably has something to do with it.

edit

http://awc.org/pdf/codes-standards/publications/nds/AWC-NDS2015-Supplement-ViewOnly-1411.pdf

2015 values are lower
fb = 1500
fv = 175
E = 1.6m

#### ChugiakTinkerer

Hey that's great news!  When the numbers are in your favor it's not a boo-boo, it's planning for the unpredictable.

When you run those calculations with the 2015 SYP, make sure to use snow loads that are specific to your roof.  The ASCE 7-10 applies a standard 0.7 factor to the ground load because roofs don't collect as much snow as the ground.  Additionally there is a roof slope factor based on the thermal properties as well as the roof material.  The bottom line is your main roof snow load will likely be about 50% of the ground load.  This means that a slide-off event that dumps on the shed roof should probably be based on that design load.

It's a helpful tutorial in navigating the ASCE 7 material.  It illustrates unbalanced snow loads well, and there is this gem about secondary roofs:

QuoteSliding snow will reduce the load on the roof of origin, but can impose significant static and dynamic loads on a lower receiving roof. Ansi standards prescribe using the entire snow load from the upper roof to adjust the value of the lower roof and defines no distribution of the load on the lower roof.

#### NathanS

Yeah, I got mixed up but after examining all of my lumber, it looks like only the 2x6 stock is SPF. All of my 2x8 - 10- 12 are SYP. I did know this when I was designing my floor and gable roof. I just forgot. The span tables for SYP are kind of middle of the road in the code book. That's why I was so surprised to see that the NDS book seems to put it far ahead of virtually all other lumber..

Thanks for the additional tips, I need to reorganize later and double check things, but for Don's calculator we sort of added in the shed roof snow load to the point load calculation. It probably isn't perfect, but I feel pretty comfortable with it.

Huge relief today... we finished the gable roof. That was one heck of a job. Especially with fall here in force.

#### Don_P

Those pics really show the changing light this time of year, pretty neat. Our mountaintops might get a dusting by the end of the week. I'm plugging holes and hoping to run some heat at work this winter.

When you look at a code table that includes several common species, or when you look at a species combination set of design values in the NDS supplement, the lowest strength species controls.

Within a species and grade, when the third party grading agencies audit member sawmills they check the quality of the grading. Periodically they pull samples and break them to make sure the wood is up to the design values we are using. When they get some low strength breaks it is reported back to the ALSC that oversees all the grading agencies. If you are on grade and breaking low, the resource is changing. The forest products labs gets involved and they all look to see if indeed the timber resource is changing. In the case of SYP after the first report they broke a whole lot of wood, decided just that, and settled on the current numbers. This prompted scrutiny of the western woods and the reports came back earlier this year with no changes needed. Southern pine is largely a plantation tree now where western woods are still mostly naturals. They made a thinking error on the plantation, biggest and fastest isn't necessarily best. Trees have a lag time after the learning is done. If we alter our practices the timber will likely get back the previous numbers. Really a good stick now is as good as it ever was but they claim I can't see what makes the weak ones weak (that is a whole nother topic  )

We typically frame with SPF unless we need the strength of SYP. To continue to have that higher strength option our local lumberyard sources #1 SYP. Dougfir is also in that range.

The big snow here some years ago, collapsed part of the grocery store, the roof at Nautilus collapsed, broke a gas line, then the roof left again, also splayed our roof a bit. We were gone building, there was no heat on, and from our neighbors description we were holding ground snow load, which was beyond design load (mother nature doesn't read the codebook for weather advice). It is not uncommon here for people to install snow guards after losing the gutters once or twice. The logic then can go from, this roof is going to clear, to, this roof is going to hold the snow. I let the engineers tease out those details and am conservative when I design.

Chugiak, good catch, load duration... you cannot add the different duration adjustments. From appendix B in the NDS, pick the shortest duration load and its load duration factor. So for this, impact with a load duration factor of 2.0. You cannot then multiply that sum by 1.15 for snow. Duration of load adjustment for connections cannot exceed 1.6.

To properly adjust the base design values the load duration factor Cd is multiplied by Fb and Fv but not E. That sum is multiplied by the other adjustment factors... wet service factor (E also if you are using green lumber, E is only adjusted for moisture and incising), then for Fb the result is multiplied by the size factor then the repetitive member factor. There are actually 8 possible adjustment factors for Fb but these are the most commonly used.

#### NathanS

Thanks for sharing all the knowledge Don.

That is interesting on why SYP was downgraded a few years ago. I know very little about wood grading - I read a bit about it in "A Timber Framer's Wokrshop" and I pretty quickly realized that for this project I just need to stick with the tables.

The span tables gave me no appreciation of how much stronger SYP is than other species. More in terms of the amount of weight it would take to break. SYP has a lower modulus of elasticity than Doug fir, which would be why it spans a little less in the code (so, SYP flexes more than Doug Fir). But just looking at ability to carry weight before breaking - SYP can span over 20% more than Doug Fir in the example I created.

#### NathanS

Quote from: ChugiakTinkerer on October 19, 2016, 03:23:20 PM
Hey that's great news!  When the numbers are in your favor it's not a boo-boo, it's planning for the unpredictable.

When you run those calculations with the 2015 SYP, make sure to use snow loads that are specific to your roof.  The ASCE 7-10 applies a standard 0.7 factor to the ground load because roofs don't collect as much snow as the ground.  Additionally there is a roof slope factor based on the thermal properties as well as the roof material.  The bottom line is your main roof snow load will likely be about 50% of the ground load.  This means that a slide-off event that dumps on the shed roof should probably be based on that design load.

It's a helpful tutorial in navigating the ASCE 7 material.  It illustrates unbalanced snow loads well, and there is this gem about secondary roofs:

Sliding Snow load = 0.4 * flat roof snow load * horizontal distance from eave to ridge of upper roof

flat roof snow load = 0.7  * ground snow load * exposure factor * thermal factor * importance factor

For my roof; exposure factor = thermal factor = importance factor = 1.0

Finally,
flat roof snow load = .7 * 50 = 35

So,
Sliding roof snow load = .4 * 35 * 12 = 168

Then, to apply this to the lower roof, the 168 psf gets distributed over a distance of 15 ft from the upper roof eave, and if the width of the roof is less than the 15 ft, the sliding load gets reduced proportionally. My lower roof has apx a 1 ft overhang + the 8 ft span = 9ft If I measure horizontally. If I measure with the roof it would be 10ft. I also think I am supposed to exclude the 2 ft under the eave from this calculation. But since I'm not sure about some of that, I'm going to be conservative and say my lower roof is 10 ft wide.

So the proportion then becomes 168 * 10 / 15 = 112

Then 112 / 10 = 11.2 psf is the sliding load. I could be extra conservative and now not include the 2 ft of roof under the eave and do 112 /8 = 14 psf

14 psf is such a tiny number compared to the ground snow load of 50psf. This was really surprising to me.

Something else interesting, they do not mention or attempt to account for the initial thump of the snow falling.

The sloped roof load is a reduction on the flat roof load. But I think it's not necessary for me to finish the calculation.

If I use Don's calculator to find my max roof load - Uniformly Loaded Beam Overhanging One Support. Using the numbers from SYP #1 - and even excluding modifiers for snow load and repetitive members, at 2x10 #1 SYP each rafter can carry 319lb per foot. Adjusting for 16" OC that is 319 / 1.33 = 240psf. Weight of the sheathing and standing seam should  be less than 3 psf.

Unless I am messing something up big time, I think that the 2x10s are already way overkill. Not even worth calculating the roof snow load to add on to the measly 14 psf from sliding snow.

#### ChugiakTinkerer

I don't mean to be a Debbie Downer, but I think you may need to adjust your calcs for Fb.  It looks like for a 2x10 the max allowable fiber stress in bending is 1050 psi.  Table 4B in the supplement is for 2"-4" thickness, and the width rows are for the rafter depth.  Thus a 2x10 is down in the 10" wide row.

On the up side, if you plug in a 1.15 repetitive factor you're up to 1207.5 psi.  For looking at snow load you can further apply the 1.15 for two-month duration loads, resulting in a Fb of 1388.6.  Running a normal beam calc on a 96" span I get a max rafter load of 2475 lbs, which works out to 232 psf.

#### NathanS

Thanks for the correction. I did take the numbers from the wrong section.

#### ChugiakTinkerer

Quote from: NathanS on October 20, 2016, 05:51:08 PM
...

It looks to be too variable to design for.  A major variable seems to be the amount of ice that has formed, which seems all but impossible to engineer for.  In my recent searches it seems like the strategy is to put snow guards on the roof to prevent sliding.

http://www.poa.usace.army.mil/Portals/34/docs/engineering/MP-01-5663,%20Minimizing%20the%20Adverse%20Effects%20of%20Snow%20and%20Ice%20on%20Roofs.pdf has some general guidance on the adverse effects of snow and ice.  Me, I'm glad I have gable end doors and will be sure not to park a snowmobile under the eaves.

#### NathanS

After 3 days of heavy rain, we got a chance to start the mudroom roof. Was very windy today - gusts around 40mph. House was completely steady even without having finished sheathing, so that was nice. It has been so windy for the past 3 days most of the fall colors are gone. Winter is knocking.

Decided to double the rafters on the mudroom. We had exactly 16, and they would otherwise just sit around for a future project or get diced into blocking.

Awesome to see this roof take shape. I think it adds so much to the house.

The grading around the house is a great starting point. This was a real test.

#### NathanS

Getting some snow tonight and tomorrow. Been a marathon trying to get the roof mostly waterproofed. I have a ~2ft strip at the top that is still open, because I need to do the air sealing on the rafters still. This strip is fully under the gable overhang, so hopefully not too much will get into the house anymore.

I forgot to take a picture of where the rafters punch through the wall. It is a monstrosity of lumber. Every stud bay has a cripple stud on each end, and then a double cripple under each double rafter.

The one barge rafter running wild still needs to be detailed, it will wrap around the corner of the house and that little portion of the mudroom roof will run up that wall a bit. I think that is the nicest way to tie the roof in with the house and make it look integral.

I find the 7-12 gable and 4-12 shed look really good together.

I also spoiled myself and finally bought Stabila levels - a 2 pack of 48" and 16" off ebay was \$99 delivered. They are awesome and will pay dividends for leveling windows, plumbing doors, and just all the finish work that will begin soon. I did check a bunch of windows and door jambs and it would make you think I know what I'm doing.

#### NathanS

Shed roof is sheathed, both gable ends are just about finished too. Just have the <2ft strip at the top of the north and south walls, and 1pc on each end of mudroom wall. Glad I don't have to carry any more big sheets up the ladder. We did clamp and rope the big ones, my wife sitting in the attic helping to pull as I pushed. Even just for the extra stability and holding them as I changed positions.

If you don't like heights don't build a 2 story house.

By the way, want to mention again zip system/Huber. The rafters were very quick to air seal because they make a stretchable flashing tape. It's not cheap, but I don't think you could properly air seal some of these penetrations without it. It was probably 32F when I was sealing everything up, and it stuck tenaciously. All the straight edges I used regular tape, and then for wrapping the top and bottom of rafters I used the stretch tape. It came out great. Before drywall and insulation I will caulk/sprayfoam the interior of those holes as a backup. Since the rafters are all double I do need to get that seam sealed from the inside.

We are probably 80% finished doing all the blocking for the sheathing, but probably only 30-40% has been nailed in from the outside. I wish I had 9ft panels and did them vertically. I'm guessing the blocking will also require a lot of custom fitting of the cavity insulation, which I have decided to spend more and go with rock wool. From what I read it is more possible to install it without lots of voids.

We have nice weather this coming week, even if some showers it will be warm. Last week got really nasty.

#### NathanS

Been really busy. Finished framing out the upstairs interior because my brother in law drove 5 hrs to wire our entire house this weekend. What an unbelievable help, and he made sure we didn't do anything stupid. He also told us about generator ready electrical panels, so we got one of those. When we lose power we can flip a switch and run a section of our panel off a generator. Something neat for the future is that the 50 amp plug we are going to install could also be connected to an inverter.. that runs off batteries.. that runs off solar or wind or some combo. Something we can grow in to.

Framing the interior was absolutely miserable. I had to sledge hammer every single wall into place because of the deflection in the 19' 1" span of the attic joists.

Ran conduit up to the peak of the house and fed the service wire through that.. barely got it through. Dawn dish soap as lube finally did the trick.

He also helped me carry the huge windows upstairs, which was an impossible job without him or another guy..they are too large/heavy/awkward + ladder for me and my wife alone. For the 5040 we also loosely tied a rope around them so my wife could keep just light tension to give a little extra stability while we climbed the ladder with 2 hands on the window and an elbow on the ladder... yeehaw. Will finish flashing the jambs and head this week. Also in addition to flashing the rough sill (with stretch tape.. yes that stuff is so amazing) I flashed the rough jamb. Also I installed a piece of bevel siding on the rough sill to give positive slope to the exterior. If the windows leak it should be very difficult for them to find wood to rot.

I will take more pics this week, it has been so much work lately haven't felt like picking up a camera after working so fast. It will actually slow down a little bit now. Although our wood cookstove is being delivered this week and at 800lbs that will be a joy to get from the road to the house.

#### Redoverfarm

Stove shouldn't be a problem with the Ford tractor until you hit the doorway.

#### NathanS

I'm worried that the stove won't fit in the bucket. I almost almost bought a fork attachment for the loader but was worried about fitment.. I think I will have a lot of use for those forks but it is also hard to spend money on something like that right now.

This is our stove - but it will be crated.

My neighbor is letting me borrow his flatbed trailer and some dolly type wheels. We were thinking we could have the freight truck lower the stove onto the trailer, and he could probably just use his pallet forks to slide it onto the trailer, or i could winch it. Then drive the trailer to our french door opening, jack the pallet up with my car jack and then push it onto the slab.

Open to any ideas.

#### Don_P

That's a beauty. Planks, pipes, plywood and come alongs have moved a lot of stuff around here.

With that grade around the house you could build a couple of very tall sawhorses for scaffold.

#### Redoverfarm

Quote from: NathanS on November 06, 2016, 07:24:49 PM
I'm worried that the stove won't fit in the bucket. I almost almost bought a fork attachment for the loader but was worried about fitment.. I think I will have a lot of use for those forks but it is also hard to spend money on something like that right now.

This is our stove - but it will be crated.

My neighbor is letting me borrow his flatbed trailer and some dolly type wheels. We were thinking we could have the freight truck lower the stove onto the trailer, and he could probably just use his pallet forks to slide it onto the trailer, or i could winch it. Then drive the trailer to our french door opening, jack the pallet up with my car jack and then push it onto the slab.

Open to any ideas.

The more you use your tractor the more you will learn on how to use your tractor.  Use 2" rachet straps and lift it with your bucket. Not exactly sure how far you are taking it but if it is being unloaded onto a trailer just a short distance you can just tram the tractor with the stove right up to the door.  Just build you a temporary platform to sit it on at the door and then with careful thinking you can use the bucket to push it inside.  PVC pipes (broom handles in a pinch) and plywood make a pretty good dolly.

#### NathanS

You've got me thinking now. Thanks.

I do have ratchet straps. Get the bucket up around it as tight as possible, ratchet'er on there and giddyup.

One thing I'm worried about is pulling back on the bucket lever and the rear wheels lifting off  . That has happened more than once with a full load of stone/and or dirt. I know, put weight on the 3 pt hitch, but I don't want to spend time on that right now while I have a house to weatherproof.

I have a healthy amount of concern. I feel confident that with the problem in my face things will start aligning. That has happened many times on the house. I couldn't say exactly how to set a rafter, or a 20 ft 2x12 ridge board, but with the problem in your face you can very quickly start eliminating the things that won't work, and you're just left with things that might work.

#### Redoverfarm

Quote from: NathanS on November 06, 2016, 08:25:35 PM
You've got me thinking now. Thanks.

I do have ratchet straps. Get the bucket up around it as tight as possible, ratchet'er on there and giddyup.

One thing I'm worried about is pulling back on the bucket lever and the rear wheels lifting off  . That has happened more than once with a full load of stone/and or dirt. I know, put weight on the 3 pt hitch, but I don't want to spend time on that right now while I have a house to weatherproof.

#### NathanS

Yeah, that makes a lot of sense. Have plenty of straps and a nylon sling that I bought for skidding logs.

Glad I don't have to get the thing up a flight of stairs.

#### NathanS

Stove's getting delivered some time tomorrow.. can't wait to get that in the house.

I installed almost all of the metal on the shed roof today - just have to do the endwall and small piece of sidewall trim. 4-12 12' off the ground is way easier to work than 7-12 25' off the ground.

Wanted to post some pics that I hadn't had a chance to take for awhile too.. will take a pic of how I am flashing the windows at some point too.

Electrical drop from where the service will come in

Stretch tape.. this stuff is amazing. Corners and round edges you kind of otherwise would need to caulk.. We popped conduit through the wall for future garage, barn, and hot tub. The hot tub is my idea, no.. demand.

Our electrical panel.. the bottom portion can be run off on site power with the flip of a switch.

For the 4-12 roof, because of the lower slope I am doing a backup flashing sometimes called 'bread pan' flashing. The top edge has a vertical fold so that anything water that gets past the z-trim and butyl tape will still have a lot of trouble getting into the wall. I will take some pics of installing the end wall trim too since it's easier to take the camera around with me now.

#### azgreg

It's looking fantastic! That mud room really breaks up the profile nicely.

#### Rys

Have been really enjoying following your build.
Would love to see pictures of the inside as well!

#### NathanS

Thanks Greg and Rys. I will get more pics of the inside - I actually took a few of the upstairs but my fancy camera is not wide angle enough to capture the rooms very well. The plans have changed a little from what we first posted back in May. Upstairs, we actually forwent the closets in the 2 spare bedrooms and just framed a straight wall. Luckily we live in an area where for some reason antique furniture goes very cheaply - so we are going to purchase armoires instead of framing permanent closets. We made this change after drawing lines on the floor back in August. The rooms are a lot more flexible without losing an entire wall.

Here's the upstairs rough framing, have to use your imagination a little bit. Also note the walls are not completely plumbed up yet, I didn't have time with doing the electrical so fast. Everything is very close, though.

The stove delivery went great. The slip had shipping weight at 1000lbs , but I think it was somewhere around 850-900 in reality. Not sure. The delivery guy got a tip, he showed us how to use straps to hook the pallet in the bucket. I probably would have spent all day dragging it on the ground. Took Redover's advice and put 5 blocks on the 3 point hitch. You can see how loaded the front tires were. This is one tough tractor.

The stove is beautiful, completely hand made right here in the USA. After folding and cutting metal roof for over a month I at least have a little more respect for how talented the craftsman who made this is. We envisioned this stove as the center piece to the downstairs, and it will fit right in.

#### Redoverfarm

Glad things worked out.  You might consider putting a carrier on your 3-point hitch.  This was actually a tarp rack on a tractor & trailer that I modified.  Anyone who welds can probably make you something similar.  Handier than the pocket on a shirt.  I use mine to carry all my tools when fixing fence, chainsaws and gas cutting firewood.  Before I would load it all in the bucket and when I got to my project and needed the bucket I would have to unload everything before I could use it.  In your case you can stack ballast to keep the rear of the tractor down.   I know you have a full plate now with the house but you might keep it in mind later.  Just something to make life easier.