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Metal Roof Question

Started by peter nap, August 26, 2009, 08:09:23 PM

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peter nap

I'm making progress on my Monitor Barn and have to make a decision. I need some advice.

I am considering a metal roof over the center (Pop up) section. I am also considering NOT insulating the metal roof.

1. Saves money but that's not the major reason.
2. I will be able to hear the rain better. Yes...that is a major factor.
3. I won't have to worry about condensation behind the insulation althoough I'm not sure about dripping inside with NO insulation. If it's gonna rain on me, the idea is out. >:(

It doesn't get especially cold in this part of Virginia and in fact, I designed it to be cool in the summer above all.
I have several wood stoves in this thing, and enough wood on my property to heat well beyond my lifespan.
Yes, I will be staying in some and it will be used as a cabin.
I'm not worried about building codes.
It is completely off grid and will remain so,

So....opinions, especially about condensation.
Thanks everyone..I couldn't have gotten this far without you.

wkheathjr

I thought you would still be able to hear it with insulation up there?  I would have to check with my dad on this because he got to have a metal roofing where he can hear it raining to help him relax and soothe after hard days of working.  I can relate to you wanting to hear it raining.

rickywashere

actually i have seen metal roofs that where open under to bottom draw moisture so bad it looks like it raining inside . but if you add couple vent on top that should fix that issue .. hope that help's but i love the sound or rain on a tin roof :)

moonhill

I have a metal roof in my mill/shop and it will drip.  I don't see it during the warmer seasons, it is the frost that builds up and when the sun hits it it melts and drips.  If it was in a cabin I would sheath it and install the tin on top of that.  I have seen roof systems boarded with flitches it was cool looking from the inside.  You may still see some of the tin, but I bet with the direct contact with the wood the tin roofing will moderate more evenly and not condense nearly as much.

Tim
This is a test, please stand by...

wkheathjr

Or if you got the money you could do metal roofing over a shingle.  That's what our neighbors did at the beach and didn't have any leaking yet.  It has been three years since and haven't seen them up there yet.  We are debating about doing that to our beach house next year but we have been debating it for couple of years though!

Ironmower

I would insulate, you won't like beiing in it in the summer. By the way, what's a monitor barn? Wood frame? metal frame? Just remember, air is the best insulator. NOT moving of course!

And yes, if you heat in the winter and cool in the summer, then you are bound too have condensation. Hot air this side, cold on the other. Condensation.... The only fix for not gettin rained on is; make sure you got plenty of pitch in the roof. That way it'll run to the walls. ;) ;D

GOOD LUCK!!!!
WM lt35 hd 950 JD

peter nap

Quote from: Ironmower on August 26, 2009, 09:21:30 PM
I would insulate, you won't like being in it in the summer. By the way, what's a monitor barn? Wood frame? metal frame? Just remember, air is the best insulator. NOT moving of course!

And yes, if you heat in the winter and cool in the summer, then you are bound too have condensation. Hot air this side, cold on the other. Condensation.... The only fix for not gettin rained on is; make sure you got plenty of pitch in the roof. That way it'll run to the walls. ;) ;D

GOOD LUCK!!!!


A Monitor barn is a pole barn with a story and a half center section and shed additions on the sides. All kinds of variations too. The center section usually, and on mine has a row of windows above the shed roof(s) and provide a lot of ventilation in the summer.

I was afraid I wouldn't be able to get away with the roofing. I saw one that had house wrap under the  purloins. Seemed to work OK but looked like Hell from the inside and I have to wonder how long it will last.

There isn't much pitch to these barns. The plans called for a 4/12 but I bumped it up to 6/12.

Brad_bb

I'm not totally clear on your design proposal- the design of the building that is.  Is it a dirt floor, concrete, gravel?  You are talking about having the inside open to the sheetmetal right?  I am working on a pole barn rennovation right now, and this building has a concrete floor, open to the sheetmetal roof.  It was also open to the outside because it used to be for animals.  I don't remember ever having condensation, but then it had plenty of airflow.  In my current rennovation, I am closing this barn, and insulating it well.  I have decided to install a dropped ceiling at the bottom of the trusses and insulate it well with a vapor barrier between the insulated ceiling and the space above that goes to the sheetmetal roof.  The interior will be heated.  The attic space above the insulated ceiling will be at ambient outside temp, but air can flow out via venting at the peak(and spaces at the top of the walls under the roof sheetmetal, so warmer air will rise.  
  It would be a shame for you to heat it with no insulation.  I just mean it's wasteful of wood, regardless of how much you have, and is more work for you to keep loading it.  I'd rather see it insulated, which would mean slower temp changes inside whether or not you have the heat on.  It's just so much more effecient and pleasant.  I'm not sure what a monitor barn is either.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

peter nap

It has a wood floor, sawn and sanded to keep the rough look without splinters.

I'm not going to have a drop ceiling.. (Right now I just have temporary sheathing until I decide what to do) If I need to provide an insulated space under the metal, I'll just foam between the rafters and add the same knotty pine that is on all the walls.

This is my Monitor plan picture. Mine has the shed portions enclosed though and I changed the roof pitch and the size.


shinnlinger

If it were me, I would put v groove pine or something funky like flitches as Moonhill suggests for appearance down first and then at least 1 row of 2 inch foam insulation (blue board or something)  You say you have plenty of wood, thats fine, but someday you won't feel like splitting and stacking so much.

I would pin the foam to the roof using 2x4s vertically with longs screws and then run strapping horizontally to screw your roof to.

I have a post on here on homebuilt foam panels or something close if you want to see this idea better.  The reason for vertical first is that it creates a vent and allows for any leaks/condensation to shed off the foam which I don't think will absorb water.

If you just have to skip the foam, I would put tar paper down over the v groove or whatever and then strap vertically (this time you could just use 1x ) and then again horizontally.  This way any condensation will run off.

For noise, I am thinking you could extend your overhangs by building up or running beefier  vertical strapping  and running your overhangs at least 2 feet.  This would allow you to hear the rain through the windows right below the overhang and give you nice siding (and open window) protection.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

peter nap

Quote from: shinnlinger on August 26, 2009, 10:18:08 PM
If it were me, I would put v groove pine or something funky like flitches as Moonhill suggests for appearance down first and then at least 1 row of 2 inch foam insulation (blueboard or something)  YOu say you have plenty of wood, thats fine, but someday you won't feel like splitting and stacking so much.

I would pin the foam to the roof using 2x4s vertically with longs screws and then run straping horizontally to screw your roof to.

I have a post on here on homebuilt foam panels or something close if you want to see this idea better.  The reason for vertical first is that it creates a vent and allows for any leaks/condensation to shed off the foam which I don't think will absorb water.

If you just have to skip the foam, I would put tarpaper down over the v groove or whatever and then strap vertically (this time you could just use 1x ) and then again horizontally.  This way any condensation will run off.

For noise, I am thinking you could extend your overhangs by building up or running beefier  vertical strapping  and running your overhangs at least 2 feet.  This would allow you to hear the rain through the windows right below the overhang and give you nice siding (and open window) protection.

Thanks shinnlinger!
Actually, I've read that post of yours and don't get a swelled head :D, but I think every post you've made for a year or so.
It's looking like that's the way I'm going to have to do it to prevent an indoor rainstorm.

I hate to use the knotty pine because it looks like I will have so much of it, it will be a little overwhelming. Might saw something else or use some of the oak I used on the floors.

Brad_bb

Ok, now I have a good picture of what you're doing.  I didn't know if you were retrofitting or what, now I see.   The idea, as I have learned lately, is to provide a vapor barrier between your insulation and the outside air.  A vapor barrier can be roofing felt, clear plastic sheeting, or even rigid foam panels so long as there are no air leaks.  I would highly suggest insulating properly.  I don't know of anyone who regretted spending more to insulate better.  It pays off in the long run.  One of the easiest solutions sould be Stress skin panels.  But it's probably not in order given the stage your at plus costs versus labor.  So I imagine you'll end up with some sort of rigid foam, as captain America suggested, or fiberglass batt held in place.  Spray-in expanding foam may also be an option depending on how your rafters are constructed and whether you want to sheath the interior side with something, maybe pine T&G?  Spray in would probably seal best and give you the best insulation.  I guess you have some thinking to do, in order to determine what you want to end up with, insulation-wise and looks-wise.  I'm all for going the extra mile. 
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

moonhill

A layer of foam on the outside would be nice, maybe if cost is an issue, just a inch and a half.  That would cut the cost of the screws and such.

To add the the venting discussion, as I mentioned in my first post, if the metal is in direct contact with a larger mass it will not condense nearly as much an maybe not at all.  There is room for air flow in the corrugation, that is if you are using a screw down roof.  It is the drastic temp changes during the night as the dark roof radiates back into the night sky creating the warm/cold spot which is needed for condensation to form.  Strapping decouples the roof from the mass of the roof deck and allows more chance for water to form. 

I really don't see that much dripping form my roof.  Also it is white in color.  If you were to have an exposed roof I would make it a light color or you may bake.   

Tim
This is a test, please stand by...

stonebroke

In livestock barns we use just one half a inch of foam to prevent condensation.

Stonebroke

shinnlinger

Just to clear it up I am the taller , better looking 'Captain Canaan'...  Captain America was only visiting....

Don't like a bunch of knotty pine eh?  Well you could pickle it or whitewash it I suppose, but then you are spending money where you don't need to.  What if you laid your foam right on your trusses/rafters and pinned as I mentioned above, and then apply sheet rock to the inside?

On a quasi related note, as it may give you an idea, On my second floor in my timberframe I used 4x8 floor joists 2ft on center.  I plan to rip a bunch of 2x2 and lay that on top of the joists in the center, giving me an inch on either side of the joist.  I then am going to pre-cut and pre-paint drywall and set them in the space between  the 2x2.  This will give me about an inch and a half to run conduit to wire ceiling lights on the first floor.  I will then put my sub-floor/floor on the 2x2.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

peter nap

Quote from: shinnlinger on August 27, 2009, 06:01:03 PM
Just to clear it up I am the taller , better looking 'Captain Canaan'...  Captain America was only visiting....

Don't like a bunch of knotty pine eh?  Well you could pickle it or whitewash it I suppose, but then you are spending money where you don't need to.  What if you laid your foam right on your trusses/rafters and pinned as I mentioned above, and then apply sheet rock to the inside?

On a quasi related note, as it may give you an idea, On my second floor in my timberframe I used 4x8 floor joists 2ft on center.  I plan to rip a bunch of 2x2 and lay that on top of the joists in the center, giving me an inch on either side of the joist.  I then am going to pre-cut and pre-paint drywall and set them in the space between  the 2x2.  This will give me about an inch and a half to run conduit to wire ceiling lights on the first floor.  I will then put my sub-floor/floor on the 2x2.

How long is your run? Unless it's fairly short it looks like you'll have to tape the rock. That looks like a PITA with the beam on either side.

shinnlinger

Peter,  Just to point out that you have hijacked your own thread...  But anyway My bent to bent distance varies but they are between 9 and 11 feet and I believe you can get 10 and 12 foot rock so I am hoping I will be all set.  Worse case though with those distances and being less than 2 ft wide, I could pre tape and mud if I had too.  That is my whole hope though, to avoid painting and taping between the beams and avoid the "too much wood" look of cardecking.  But I also get an advantage of being able to run wires in the cavity.  I thought of putting foam in there too as a sound stopper, but it is an added expense and I plan to heat with wood so I think I want the heat to be able to rise to the second floor.
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

peter nap

Quote from: shinnlinger on August 27, 2009, 07:54:22 PM
Peter,  Just to point out that you have hijacked your own thread...  But anyway My bent to bent distance varies but they are between 9 and 11 feet and I believe you can get 10 and 12 foot rock so I am hoping I will be all set.  Worse case though with those distances and being less than 2 ft wide, I could pre tape and mud if I had too.  That is my whole hope though, to avoid painting and taping between the beams and avoid the "too much wood" look of cardecking.  But I also get an advantage of being able to run wires in the cavity.  I thought of putting foam in there too as a sound stopper, but it is an added expense and I plan to heat with wood so I think I want the heat to be able to rise to the second floor.

Yeah...I know I hijacked it, but as usual, the question was answered pretty thoroughly.

OTOH, your idea of the sheetrock panels is genius. Guess I should have started another thread though.

shinnlinger

Peter,  I need you to talk to my wife...  Glad SOMEONE likes my ideas.

Stonebroke,  I am curious about how you apply the 1/2 inch foam insulation in a livestock barn.  Do you throw it on top of the rafters/straping and pin it with the metal roofing?  Do you nail it to the inside face of the rafter/truss?
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

peter nap

Quote from: shinnlinger on August 28, 2009, 12:07:56 PM
Peter,  I need you to talk to my wife...  Glad SOMEONE likes my ideas.

Got the same problem. You should have seen her face when I drew up plans to take two fourty foot cargo containers and put trusses over the open space :D :D :D :D :D :D :D :D :D

stonebroke

Generally they put it on top of the rafters and pin it with the metal roofing. Alittle bit is effective in preventing condensation because the dew point will be in the insulation( I think)

Stonebroke

peter nap

Quote from: stonebroke on August 28, 2009, 04:59:39 PM
Generally they put it on top of the rafters and pin it with the metal roofing. Alittle bit is effective in preventing condensation because the dew point will be in the insulation( I think)

Stonebroke

I guess the big question would be, will it stop the condensation when there's a wood stove going under it?

Brad_bb

Peter, So have you come to a conclusion of what you are going to do, or at least a leading contender?

shinnlinger, I never heard of captain Canaan.  I did have Captain America stuff when I was a kid though. 
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

peter nap

Quote from: Brad_bb on August 28, 2009, 07:04:44 PM
Peter, So have you come to a conclusion of what you are going to do, or at least a leading contender?

shinnlinger, I never heard of captain Canaan.  I did have Captain America stuff when I was a kid though. 

Working on it Brad. I've always gotten good advise here and actually took most of it.

I am not going to do the bare roof/ceiling like I was thinking about.
I do want a metal roof so I need to decide which route to take.
I also like Shinnlingers ceiling panels and am trying to incorporate it (I really hate taping sheetrock).

stonebroke

I would say it probably  would stop condensation with a wood stove.

Stonebroke

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