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Old 05-10-2013, 08:02 AM   #1
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8x12 Gable Shed - Roof Help


Hey guys, I am in the process of building an 8x12 gable shed, the floor is done and have the walls up so today mocked up 12/12 pitch rafters and also 5/12 pitch rafters. Will post some pictures shortly.

But basically liking the look of the steep 12/12 pitch for the roof.

My plan is to build the rafters out of 2x4 on 16" centers with 7/16" OSb sheathing, will be open cathedral but will run some collar ties maybe 1' or 2' below the peak for strength and eventually one day will put a loft on one side for extra storege space. Wondering if this makes sense....I could use 2x6 rafters but at same time also seen people use 2x4.

Now the bigger question I have is the actual sheathing and shingling part of it....espeicially if I decide to go with 12/12. I have helped buddies and familly members reshingle there houses in the past, but guessing these pitches as they were ranch houses were probably in the range of 3/12 or 4/12 or 5/12 and were easy to move around on. Now this 12/12 and after looking at my mock-up rafter it looks pretty darn steep!

If I go with the 12/12 roof, and to do the sheathing and shingles safely how should I tackle this pitch???

1.) Install some roof jacks that take a 2x10 board. So I have a base to stand on and kneel against...would adjust left and right as needed and also raise as need to get up to the top.
2.)Was also thinking about building a quick ladder out of 2x4's that I could hang over the top edge when I need to get to the top.
3.) Scalffolding - can rent and prices seem good some scafolding to have a base to stand on located just below eaves.
4.) I do have a safety harness (thinkinng it is a linesman) that goes around your waist (does not go around shoulders or legs just the waist), was given to my Dad from my Grandpa for working on the farm and getting up on bins and pole barn. So thinking to throw this on and just tie a rope over the roof and secure on the other side. Would adjust the slack so it stops right at the eaves.

Yep, just making sure to do this safely as possible and will have my brother helping so looking out for both of us for the sheathing and shingly part.

Any tips...ideas....will post some pictures soon showing the wimpy 5/12 versus the awesome 12/12 roof mock-up!
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Old 05-10-2013, 08:20 AM   #2
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8x12 Gable Shed - Roof Help


2x10 roof jacks, and a real harness not that backbreaker safety belt you have.
Install the first row of plywood and a few courses of shingles off a ladder, until the plank will be at a comfortable height to get on, I usually do 6 rows of shingles. No reason you cant do less to make the plank lower, of course
Since it isn't very tall, you can probably get away with just one row of planks.

If you aren't comfortable on a ladder,pipe staging will make this very simple and safe. If your going that route it might be cheaper to hire someone.

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Old 05-10-2013, 09:10 AM   #3
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8x12 Gable Shed - Roof Help


In my experience there is no part of framing a roof that has been screwed up more than the use of a tied rafter. Although the math is not all that complicated, people think that they can just throw in a couple of rafter ties and call it a day, with little to no regard for the anticipated dead and live loads that will be applied. This has obviously been going on for ages, that's why you see so many old garages with their walls bowed out. For some reason, people cannot seem to understand the forces involved. I have said this before, but picture yourself with one foot on the dock, and one in the boat. and the boat is not secured to the dock. We know where you are going, and I hope its in the summer time.

The biggest 2 problems I have found are:

1. The rafter tie is placed way too high, that is, way to close to the apex of the roof. I suspect that people are confusing a rater tie and a collar beam. BIG Difference. There are usually floor joists serving as a tension tie (Thanks GaryB) when a collar beam is used to finish an attic.

One third of the way up from the wall is usually the height limit for the cross tie on a tied rafter. Think of the leverage that is applied as the bottom of the rafter is forced upward by the implied loads. Basically the rafters want to do a split. The rafter tie is arresting that force.

2. The fasteners to tie the rafter to the tie. Nails do not cut it here. Nothing to do with the shear strength of the nail, everything to do with the strength of the wood. Use Minimum (2) 1/2 inch bolts on each side with large flat washers, and tighten them till the washers just punch into the wood. I would use minimum 2 x 6 dimensional lumber regardless of size of shed.

To answer your roofing question, about 6.5 to 7 in 12 is the most comfortable slope to shingle comfortably IMO. This presents the shingles to you nicely for nailing, and is plenty of slope for good drainage. How to install the shingles is right on the package, and is on every manufacturers website. To get your exposure equal, run your first course, then hook your tape to the end of the course, pull your tape out right to the ridge, then rotate the top of your tape till the tape reads a number evenly divisible by the exposure. Mark your courses with grease pencil on your felt, then pop your lines.


Re Rafter ties, I found this calculator to help:

http://www.timbertoolbox.com/Calcs/raisedtiethrust.htm
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Last edited by jagans; 05-10-2013 at 12:53 PM.
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Old 05-10-2013, 09:12 AM   #4
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8x12 Gable Shed - Roof Help


I agree with PatChap, staging and jacks would be the best way to go. Belts are not allowed in a lot of areas anymore because they are misused and people get hurt. I don't think I'd use a full harness either, as you don't have enough height to do it properly.
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Old 05-11-2013, 12:34 PM   #5
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Hi jagans, thanks for the help. So if the distance from the wall plate to peak is about 4', could I locate the rafter tie about 2 1/2 feet above wall plate? Will use bolts like you said.

Also wondering as I will have about 9 or 10 rafters, would it be ok if the first rafters ties from each end are set right on the wall plate- these I would use for a loft type shelf. And the the middle section keep the rafter ties up higher for the extra headroom?
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Old 05-11-2013, 12:37 PM   #6
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8x12 Gable Shed - Roof Help


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One third of the way up from the wall is usually the height limit for the cross tie on a tied rafter.
if the ridge is 48" above the top plates then 1/3 of 48" would be 16", your other option would be to install a ridge beam which would support 1/2 the roof load. this eliminates the rafter thrust (weight pushing down on rafters) which in turn want to push the tops of the walls outward. ceiling joists and rafter ties are two options for keeping the tops of wall from being pushed outward from the weight of the roof. if you want head room within the shed the ridge beam might be the best option.

where are you located? location helps to determine roof loads. you may want to edit your profile to include your location as many times answers to your questions are location based.
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Old 05-11-2013, 12:46 PM   #7
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Quote:
Originally Posted by jagans View Post
http://www.timbertoolbox.com/Calcs/raisedtiethrust.htm
some nice calculators found on http://www.timbertoolbox.com/ .....
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Old 05-11-2013, 02:22 PM   #8
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8x12 Gable Shed - Roof Help


Are those just 2 X 4's used to frame the floor?
What's holding this up off the ground? I can not see any supposts.
No ridge pole, and no over hangs going to be on the gable ends?
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Last edited by joecaption; 05-11-2013 at 06:03 PM.
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Old 05-11-2013, 03:23 PM   #9
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8x12 Gable Shed - Roof Help


Quote:
Originally Posted by wguttrid View Post
Hi jagans, thanks for the help. So if the distance from the wall plate to peak is about 4', could I locate the rafter tie about 2 1/2 feet above wall plate? Will use bolts like you said.

Also wondering as I will have about 9 or 10 rafters, would it be ok if the first rafters ties from each end are set right on the wall plate- these I would use for a loft type shelf. And the the middle section keep the rafter ties up higher for the extra headroom?
Well I guess you could, but as Gary said your intermediate ties should be about 16 inches up slope from the plates. The end ties would really be more like ceiling joists so no problem at all with them. You could increase the slope of the roof, therefor increasing the distance from the top plates to the ridge so that would move the ties up a little. I will be building a shed this summer and I plan on useing longer studs for the walls to increase the headroom. That is the easiest solution in my opinion, but it requires more siding. You can probably get away with using a combination of moving the ties up some, and using a ridge board and a plywood gusset at the peak, as the rafter run is not very long at all, and judging by the length of your lookouts, you actually have a cantilever effect going on there.

Lets face it, we have all seen sheds that are built a heck of a lot weaker than what you are planning on by following our advice, and worst case scenario is you could add some support down the road if need be.
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Old 05-17-2013, 07:02 AM   #10
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8x12 Gable Shed - Roof Help


Gbrackins - thanks for the calculator.

joecaption - I have three rows with four sets of blocks underneath that have resting on top a 4x4...think it is just the angle of the camera and the small clearance to the gravel base. Ya ended up gettting a great deal on the 2x4 PT that I used for the floor that I just could not pass up. It was just a quick mock up I did in this picture....I am gonna use either a 12' or 14' 2x4 for the ridge beam-pole (not sure which one is proper language).

jagans - thanks for the advice....

It is the long weekend holiday in here and hoping I can get the roof framed up this weekend....just finished siding it this week which by the way doing by yourself is a reall pain in the ass.


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