Question about a roof design

[cdestuck]

I have sort of a odd question about a roof I'm building behind my garage. My garage is 40' wide and I have a small bit of property behind it, angled property in because their all anything but straight in my neighborhood. So I building a shed type roof back there for some dry storage. At end of the garage I have 7' of depth and 40' away and the other end of the garage there is 14'depth. See my crude sketch attached.

So I have attached a ledger and joist hangers to the rear garage wall and a double 2 x 10 beam at the property line, at the angle I described. I'm hanging my 2 x 8 joists starting at the 7'deep end. So I'm halfway done, about 20'. Out of curiosity I measured the height of the 1st joist where it crosses the beam which was 92''. So I measured the joist 20' away going towards the 14' deep end and this height is about 1 1/2'' shorter. So when I get all the way to the deep end, my joist height looks to be about 3'' shorter than the 7' deep end.

Is this what should be happening with a beam set at an angle from the garage wall? I did run a string line along the top of the set joists and the string touches all the joists at the same plane. what steps would normally be used when building to keep the joist all at the same height? I imagine that I could cut the birds mouth at diff depths to keep joists all the same height. What else could I have done? I've thought of shimming each joist but that seems sort of hokey.

 

[astroracer]

The first question I have to ask is how far off the property line are you? Many codes require at least 10' some even more. If you are not to code you may end up tearing down what you are building. Any permit required to build the lean-to?
Post up some pics. It'll be easier to see what you are doing.
Mark

 

[JustinBravo]

I have sort of a odd question about a roof I'm building behind my garage. My garage is 40' wide and I have a small bit of property behind it, angled property in because their all anything but straight in my neighborhood. So I building a shed type roof back there for some dry storage. At end of the garage I have 7' of depth and 40' away and the other end of the garage there is 14'depth. See my crude sketch attached.

So I have attached a ledger and joist hangers to the rear garage wall and a double 2 x 10 beam at the property line, at the angle I described. I'm hanging my 2 x 8 joists starting at the 7'deep end. So I'm halfway done, about 20'. Out of curiosity I measured the height of the 1st joist where it crosses the beam which was 92''. So I measured the joist 20' away going towards the 14' deep end and this height is about 1 1/2'' shorter. So when I get all the way to the deep end, my joist height looks to be about 3'' shorter than the 7' deep end.

Is this what should be happening with a beam set at an angle from the garage wall? I did run a string line along the top of the set joists and the string touches all the joists at the same plane. what steps would normally be used when building to keep the joist all at the same height? I imagine that I could cut the birds mouth at diff depths to keep joists all the same height. What else could I have done? I've thought of shimming each joist but that seems sort of hokey.

It sounds like your question should be directed to a professional builder or carpenter who is experienced with roof frames and joints. As far as general overview of roof styles appropriate for garages and sheds, this article details most popular styles, design elements, and their pros and cons: http://www.remodelingimage.com/top-20-roof-types-plus-design-elements-and-costs/

 

[DougWil]

Does this shed roof have any slope? I hope so.
If so, the farther away from that level ledger the lower the elevation at the beam.

 

[Playwme]

You have to make a choice here. If your beam is level, then the roof pitch will vary as it goes along and appear to have a twist in it. If you want the roof flat , then your beam needs to be higher at the 7 foot end. Theoretically it should be halfway between the height of the 14 ft end and the height of the ledger.

After rereading your post, where are you measuring the 92 inches from? Is the ground perfectly level, and the beam too?

 

[TractorJeff]

To get the roof all at the same pitch, you need to set your double 2x10 beam at the 7 foot mark for the 40 feet. You can not do it at an angle! This is what is causing the roof to appear with a pitch in it and lower at the long end of it.

 

[cdestuck]

The first question I have to ask is how far off the property line are you? Many codes require at least 10' some even more. If you are not to code you may end up tearing down what you are building. Any permit required to build the lean-to?
Post up some pics. It'll be easier to see what you are doing.
Mark

Luckily there is no set back from the property line at this location.

 

[cdestuck]

Does this shed roof have any slope? I hope so.
If so, the farther away from that level ledger the lower the elevation at the beam.

Of course I do. At the 7' starting depth, there is about 18" drop. Plus I'm using metal roofing so there is no worry about rain backing up under shingles. Going to put in some clear polycarbonate panels for light into the rear garage windows.

 

[DougWil]

Of course I do. At the 7' starting depth, there is about 18" drop.

OK, does that mean you have 36" of drop at the 14' end depth?
If so, and the ledger is level, and the joists are perpendicular to the 40' wall, you have a flat plane.

So what is the issue?

 

[cdestuck]

From the garage out to the beam at 7', there is a pitch of 18". But as I add the joists, working towards the other end which is 14' deep, I can see that the headroom under the joists is dropping. Now I figure it will drop about 3" til it get clear to the end. I can live with that but I was just wondering what could I do if I had to maintain the same headroom at both ends.

 

[joe_padavano]

This is just trig. The beam needs to be higher at the 7' end than at the 14' end to keep the pitch of the roof constant. If we had all the pertinent dimensions, this would be pretty simple to lay out.

 

[DougWil]

From the garage out to the beam at 7', there is a pitch of 18". But as I add the joists, working towards the other end which is 14' deep, I can see that the headroom under the joists is dropping. Now I figure it will drop about 3" til it get clear to the end. I can live with that but I was just wondering what could I do if I had to maintain the same headroom at both ends.

Put the beam in level and the ledger in with a pitch.

 

[timewarp]

Or put the Beam and the ledger level and have variable pitch roof, your sheathing and roofing material will twist that much with no problem.

 

[Radix2]

From the garage out to the beam at 7', there is a pitch of 18". But as I add the joists, working towards the other end which is 14' deep, I can see that the headroom under the joists is dropping. Now I figure it will drop about 3" til it get clear to the end. I can live with that but I was just wondering what could I do if I had to maintain the same headroom at both ends.

Your description is not making sense.

You say you are measuring the height at the beam... if the beam is level, the height is the same...?

If you want the roof to to a single plane and not twisted, assuming you set the ledger level to some point on your garage - then you need to make the beam follow the angle of the roof pitch at the distance it is from the garage.

You say you have 18" of fall at 7 feet at one end. You therefore need to lower the beam at the other end by 18" so that you have 36" of fall at that end( twice as far out, twice the fall). Your roof will not be twisted.

There is no way with a level ledger board that you can have the same headroom at 7 and 14 foot spans at the beam...and a flat roof.

If you really want that, you need to make the beam level and make the ledger board rise by 18" over the length - with it 18" higher at the 7 foot end.

The last alternative is simply to make both level and live with a twist that has half the roof pitch at one end as at the other.... might look cool, might look like a hack job.

I have no idea on your 3" difference you are seeing, it just sounds like you don't have the beam level (level it) and you are building the twisted roof alternative.

 

[cdestuck]

Your description is not making sense.

You say you are measuring the height at the beam... if the beam is level, the height is the same...?

If you want the roof to to a single plane and not twisted, assuming you set the ledger level to some point on your garage - then you need to make the beam follow the angle of the roof pitch at the distance it is from the garage.

You say you have 18" of fall at 7 feet at one end. You therefore need to lower the beam at the other end by 18" so that you have 36" of fall at that end( twice as far out, twice the fall). Your roof will not be twisted.

There is no way with a level ledger board that you can have the same headroom at 7 and 14 foot spans at the beam...and a flat roof.

If you really want that, you need to make the beam level and make the ledger board rise by 18" over the length - with it 18" higher at the 7 foot end.

The last alternative is simply to make both level and live with a twist that has half the roof pitch at one end as at the other.... might look cool, might look like a hack job.

I have no idea on your 3" difference you are seeing, it just sounds like you don't have the beam level (level it) and you are building the twisted roof alternative.

Gee I'm so messed up on this rt now. I'm not where this is at for a few days or so. I'm gonna have to get there, do some sting lines with my line level. I'm pretty sure the concrete is level but I'll have to recheck. I appreciate all the input you all have given me. Good stuff to ck against my work.

 

[cdestuck]

This is just trig. The beam needs to be higher at the 7' end than at the 14' end to keep the pitch of the roof constant. If we had all the pertinent dimensions, this would be pretty simple to lay out.

Oh my, trig. That word alone still scares me.

 

[gregtwojeeps]

Is my sketch (not to scale) anything close to what is trying to be done by the OP ?

 

[lakeroadster]

Oh my, trig. That word alone still scares me.

We Ain't Scared... we'll use mad Cad skills....

Or put the Beam and the ledger level and have variable pitch roof, your sheathing and roofing material will twist that much with no problem.

Is my sketch (not to scale) anything close to what is trying to be done by the OP ?

I am thinking this would also be my recommendation. Having both level with the world.... but I'd make a drawing of it first to see what it looks like.

I'd be glad to create a CAD model for you if you give me the dimensions. That allows you to see a 3 dimensional version.. a preview of coming attractions, so to speak

Just reply here with the data requested.. see modified version of gregtwojeeps drawing, shown below.

Also, what color is the steel and trim for this, so I can make it look a bit more real world?

 

[cdestuck]

We Ain't Scared... we'll use mad Cad skills....





I am thinking this would also be my recommendation. Having both level with the world.... but I'd make a drawing of it first to see what it looks like.

I'd be glad to create a CAD model for you if you give me the dimensions. That allows you to see a 3 dimensional version.. a preview of coming attractions, so to speak

Just reply here with the data requested.. see modified version of gregtwojeeps drawing, shown below.

Also, what color is the steel and trim for this, so I can make it look a bit more real world?

Wow, that is exactly what my project will look like. I will get back there in the morning and get you those measurements. Thanks tons guys

 

[cdestuck]

Is my sketch (not to scale) anything close to what is trying to be done by the OP ?

Yes you drew exactly what my project will look like. As to the post following yours, I will get those measurements Sunday morning and post. Tks

 

[Radix2]

Is my sketch (not to scale) anything close to what is trying to be done by the OP ?

You simply cannot have the beam and the ledger both level and not parallel with a planar roof as your drawing implies. As shown on the drawing, the roof is twisted with twic the slope at one end vs the other. Possible, but odd and it seems not his intention.

he could make the ledger and beam parallel and level, with the overhang varying, but then that is back to a falling eve.

Another alternative is both ledger and beam are sloped, the roof is planar but sloped in two directions, the eve is level.

CD - is a twisted roof ok with you?

 

[gregtwojeeps]

I am not following your reply very well Radix. My sketch depicts a level ledger attached to the garage and a level beam...same plane of axis. The end of the beam is around 7 ft. away from the wall on one end, about 14 ft. away from the garage on the opposite end. My sketch is NOT to scale..

What I cannot draw ( I am not an architect or engineer) is that the beam on the 14 ft., end will be out of the grade substantially higher than the beam will be on the 7 ft. end. If the OP does not want his 14 ft. end that high out of the ground, then yes, the roof will have a "twist" to it. Hopefully if Lakeroadster gets true numbers from the OP he can CAD out a drawing to scale, where it makes sense to me and the OP and to all reading. JMO

 

[cdestuck]

We Ain't Scared... we'll use mad Cad skills....





I am thinking this would also be my recommendation. Having both level with the world.... but I'd make a drawing of it first to see what it looks like.

I'd be glad to create a CAD model for you if you give me the dimensions. That allows you to see a 3 dimensional version.. a preview of coming attractions, so to speak

Just reply here with the data requested.. see modified version of gregtwojeeps drawing, shown below.

Also, what color is the steel and trim for this, so I can make it look a bit more real world?

Lakeroadster, Here are the dimensions for the CAD

A= 40'
B= 14'
C= 7'
D= 88"
E= 102"
F= 102" (E is butted up against F)
G= 2''x8''x40'
H= Doubled 2x10
J= 2x8 16''oc
K= 10/12

Roofing will be gray corrugated metal, garage roof is dark brown

Thanks so much for doing this. Wayout of my League.

 

[davejo]

your pitch isn't 10:12

you said it drops 18 inches in 7 feet before so its 2.6:12

You haven't said if the beam is actually level, rather you suggest that the beam is out of level about 3 inches over 40 feet.

The way you are describing it is giving you a variable pitch that will start at 2.6 (steeper)at the 7 foot end and progress to 1.3:12 (flatter) at the 14 foot end.

Since you are doing a variable pitch, your beam being out of level 3 inches probably isn't going to matter to those looking at your freestyle design.

 

[lakeroadster]

Pretty basic model... hope this helps. These are merely for a "visual". Sizes of components are as specified by cdestuck, as listed below.

Unless otherwise noted these are all shown as "perspective" views, which are more realistic.

Orthographic views as a visual, IMO, aren't "real world".

Ledger and beam are level,
Rafters are square with the building,
Roof pitch on the barn is drawn at 10/12
Roof pitch on the lean-to varies.

Lakeroadster, Here are the dimensions for the CAD

A= 40'
B= 14'
C= 7'
D= 88"
E= 102"
F= 102" (E is butted up against F)
G= 2''x8''x40'
H= Doubled 2x10
J= 2x8 16''oc
K= 10/12

Roofing will be gray corrugated metal, garage roof is dark brown....

 

[gregtwojeeps]

your pitch isn't 10:12

you said it drops 18 inches in 7 feet before so its 2.6:12

You haven't said if the beam is actually level, rather you suggest that the beam is out of level about 3 inches over 40 feet.

The way you are describing it is giving you a variable pitch that will start at 2.6 (steeper)at the 7 foot end and progress to 1.3:12 (flatter) at the 14 foot end.

Since you are doing a variable pitch, your beam being out of level 3 inches probably isn't going to matter to those looking at your freestyle design.

I think Lakeroadster is denoting "K" on my sketch as the garage roof pitch, not the shed roof pitch. And yes, a 10/12 reads a bit high for a garage but I am sure the OP will come back and verify if he mis-stated it. The garage pitch is just needed for the CAD layout presentation, as it will have no effect on the sheds needed slope to drain. JMO

 

[cdestuck]

Wow that's really nice. Appreciate your work. Yes my garage roof is steep. Front is 12/12 and back is 10/12. I wanted attic trusses when garage was built for plenty of storage.

 

[lakeroadster]

I revised the views above to show a 10/12 pitch.

So, you ok with the "variable pitch... a.k.a. twisted roof" concept?