Shed Roof Question

[mbrule]

While not a tractor project, it is the shed that keeps my little tractor warm and dry.

The shed is an addition on the back of my garage. It is effectively a lean-to attached to the back of my garage. Because it is attached to the back wall, the roof is not properly vented on that end. The other end is well vented in the bottom of the 12 inch overhang (I think it is called the soffit), and has spacers to allow airflow above the roof insulation. The roof also has very little pitch. The building is insulated and sheet-rocked and heated all the time. In a nutshell, very low pitch improperly vented roof = Ice damns and leaks. Usually our winters in Mass are not this bad and as long as I pull the snow from the edge of the roof everything is OK.

Now, after this last month, I want to do something about this issue. The roof is about 10' x 15' (don't remember exactly). I could add heat wires to the roof and gutter. I don't want to get into rebuilding the roof correctly, as that would involve messing with the recent garage roof as well.

My question: Is there some other roofing material (steel, EPDM, ?) that I could use where the poorly-vented, low slope roof would not be a problem? Said material would have to interface to the shingle roof coming from the garage as well. The shed roof and garage roof come together as one roof at the wall.

What say the TBN roofers?

 

[radioman]

Well- if you quit heating that space- you wouldnt have ice issues. However - since you already have ice- you might want to think abot switching to metal roof. the snow doesnt like to stay up there and it heats up quicker then shingles does from the sun when the top portion is exposed to sun and ice doesnt stick very well when heat up from sun.

 

[roadhunter]

Had a similar situation on a project I was working on recently and ended up going to a metal roof.

 

[mbrule]

Well- if you quit heating that space- you wouldnt have ice issues. However - since you already have ice- you might want to think abot switching to metal roof. the snow doesnt like to stay up there and it heats up quicker then shingles does from the sun when the top portion is exposed to sun and ice doesnt stick very well when heat up from sun.

Thanks for the reply, Yes, not heating would solve the problem, but it is the furnace for the garage, and I do want that heated. It also keeps my tractor warm and ready to go. Metal certainly seems like an option, what I wonder about it is, how it would interface to the shingled garage roof. The roof on the whole building is only a few years old and I do not want to replace the garage roof it has plenty of pitch and proper ventilation.

Thanks for any and all replies!!

 

[GLyford]

There is a way to do flashing under your main roof so that the shingles drain out onto the metal, you don't have to change the main roof* when you change over the leanto. Proper installation of the metal roof also uses butyl tape to seal panels together, which I would think would be wise due to your low slope and ice-dam forming conditions.

Is the ceiling of the leanto insulated up against the roof, or is there an airspace between the roof decking and the insulation? If there is an air space, is there perhaps a way to add vent at either end of the leanto roof near the garage end to circulate more outside air to help keep it cooler?

* OK, you might have to shorten the first row some to make room for the height of the metal roof profile and the flashing...

 

[DFB]

Can't you add louvered vents on both gable sides to help with airflow?

Sounds like a heat loss though.

 

[mbrule]

There is a way to do flashing under your main roof so that the shingles drain out onto the metal, you don't have to change the main roof* when you change over the leanto. Proper installation of the metal roof also uses butyl tape to seal panels together, which I would think would be wise due to your low slope and ice-dam forming conditions.

Is the ceiling of the leanto insulated up against the roof, or is there an airspace between the roof decking and the insulation? If there is an air space, is there perhaps a way to add vent at either end of the leanto roof near the garage end to circulate more outside air to help keep it cooler?

* OK, you might have to shorten the first row some to make room for the height of the metal roof profile and the flashing...

The ceiling is insulated between the rafters, There is an air gap against the roof (used the foam things designed for this purpose). Because the roof comes up against the garage wall at the top, I would have to drill through a couple of 2x6s that form the header. That would vent it into the heated garage. I could then likely do some more cutting through the loft floor and then box all that in and insulate to vent to the unheated loft, but it would not be easy. This is an old building that I have hacked together, and I clearly only new enough to be dangerous when I did it!!!! I did not plan on heating all the time when I did it either.

So now I am pretty much looking for a "band aid" approach to fix it, knowing that it is less than ideal.

 

[mbrule]

Can't you add louvered vents on both gable sides to help with airflow?

Sounds like a heat loss though.

It is heat loss for sure. There is no gable here, it is a "lean to". The garage has gable vents, ridge vents, and soffit vents on the other end (also no ideal, but works!). Obviously no soffit vents where the lean to joins.

 

[DFB]

Well when I use term gable its the "end" side of your lean too I am referring as opposed to eave which you have said is ventilated. How do you think the heat is escaping thru the existing insulation

 

[GLyford]

OK, how about putting another section of the spacers along the garage wall, so the other end of the rafter space opens down. Make a chase along the bottom of the rafters along the wall to tie all these rafter space ends together, and insulate it from the open area. Have a vent at each end of chase out through the end sheathing. It likely wouldn't thermosiphon like it would if the openings were higher, but it might allow wind/breeze to help pump air in/out of the space? This is assuming that the lean-to side of the garage wall isn't already full of shelving etc. that would be in the way.