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Home > Archive > Architecture > December 2005 > Ridge flashing?
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| Ridge flashing.
Say what?
I'm wondering if the galv. sheet metal material that is used in roof
valley's couldn't be flipped upside down and nailed on the peak, and hip
ridges (8d @ 8" o/c) of a roof.
As it is right now, once the high velocity wind snatches the ridge shingles
loose (the most common damage to happen in a hurricane because of the nature
of how ridge shingles are) the air than gets into the seam between the
plywood sheathing and peels the whole thing back and then disaster occurs.
But if the sheet metal was installed the wind would not be able to get into
the plywood seam.
If ridge and valley cats were installed too this would cause a structural
integrity to occur in what seems to me to be a weak point in the system of
roof failure during high velocity winds.
Of course any *upgrade* such as this has a cost factor involved but the cost
for the material and labor is minimal, probably less than $200 per 1500 s.f.
home, and the benefit is huge.
Waddya think?
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| 3D Peruna 2005-12-23, 11:21 am |
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"Don" <one-if-by-land@concord.com> wrote in message
news:XITqf.8815$3Z.5591@newsread1.news.atl.earthlink.net...
> Ridge flashing.
> Say what?
> I'm wondering if the galv. sheet metal material that is used in roof
> valley's couldn't be flipped upside down and nailed on the peak, and hip
> ridges (8d @ 8" o/c) of a roof.
> As it is right now, once the high velocity wind snatches the ridge
> shingles loose (the most common damage to happen in a hurricane because of
> the nature of how ridge shingles are) the air than gets into the seam
> between the plywood sheathing and peels the whole thing back and then
> disaster occurs.
> But if the sheet metal was installed the wind would not be able to get
> into the plywood seam.
> If ridge and valley cats were installed too this would cause a structural
> integrity to occur in what seems to me to be a weak point in the system of
> roof failure during high velocity winds.
> Of course any *upgrade* such as this has a cost factor involved but the
> cost for the material and labor is minimal, probably less than $200 per
> 1500 s.f. home, and the benefit is huge.
> Waddya think?
What do you use for venting of your roofs? Up here, lots of people use
ridge vents, so the system would need to provide an adequate net free vent
area.
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| RicodJour 2005-12-23, 1:21 pm |
| Don wrote:
> Ridge flashing.
> Say what?
> I'm wondering if the galv. sheet metal material that is used in roof
> valley's couldn't be flipped upside down and nailed on the peak, and hip
> ridges (8d @ 8" o/c) of a roof.
> As it is right now, once the high velocity wind snatches the ridge shingles
> loose (the most common damage to happen in a hurricane because of the nature
> of how ridge shingles are) the air than gets into the seam between the
> plywood sheathing and peels the whole thing back and then disaster occurs.
> But if the sheet metal was installed the wind would not be able to get into
> the plywood seam.
> If ridge and valley cats were installed too this would cause a structural
> integrity to occur in what seems to me to be a weak point in the system of
> roof failure during high velocity winds.
> Of course any *upgrade* such as this has a cost factor involved but the cost
> for the material and labor is minimal, probably less than $200 per 1500 s.f.
> home, and the benefit is huge.
> Waddya think?
You don't use metal strapping across the top of the ridge tying the
opposing pair of rafters together? I thought it was required in all
high wind areas. Easiest way to do it and a hell of a lot stronger
than flashing.
R
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| > Easiest way to do it and a hell of a lot stronger than flashing.
If I understand the proposal correctly, it is to prevent the need for
strength.
"At IBM we practice efficiency."
"At Digital we don't piss on our hands."
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| RicodJour 2005-12-23, 2:21 pm |
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gruhn wrote:
>
> If I understand the proposal correctly, it is to prevent the need for
> strength.
>
> "At IBM we practice efficiency."
> "At Digital we don't piss on our hands."
Can either IBM or Digital prevent hurricanes? How can you prevent the
need for strength? Well...Don's moving, but that's cheating.
R
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"3D Peruna" <w!h#a$r%o^l&d@w!e#i$r%d&n*e(s)s.com> wrote in message
news:X6Uqf.2116$dl.1227@fe07.lga...
>
> "Don" <one-if-by-land@concord.com> wrote in message
> news:XITqf.8815$3Z.5591@newsread1.news.atl.earthlink.net...
>
> What do you use for venting of your roofs? Up here, lots of people use
> ridge vents, so the system would need to provide an adequate net free vent
> area.
Soffit and Ridge venting is standard around here.
This post doesn't address any venting issues, which become moot in the event
of a destroyed roof.
Both types of venting need to be revamped as they are weak.
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| "RicodJour"> wrote
> Don wrote:
>
> You don't use metal strapping across the top of the ridge tying the
> opposing pair of rafters together? I thought it was required in all
> high wind areas. Easiest way to do it and a hell of a lot stronger
> than flashing.
Yes, strapping is used from rafter to rafter over the ridge beam.
Rafters are seldom used around here, maybe 1 house in 100 have rafters, the
other 99 are trusses.
I was thinking of this after I sent my post, that I bet most people are as
unaware as I was prior to Charley last year just how powerful and
overwhelming cat5 winds are.
It can't really be appreciated by words alone.
In 39 years of living here I had never experienced anything like it.
Sustained high winds, and microbursts, over several hours will take its
toll, so thats why I am focusing on seeming *little* things that may not
seem significant.
Little things can quickly turn into disaster in the cat 5.
From the ground up I am developing a game plan of many small issues to
address so that the average home might survive a cat 5.
I believe that for less than $5k more an average new home can be built that
will survive a cat 5 will little to no damage.
In all things of course quality control is paramount.
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"3D Peruna" <w!h#a$r%o^l&d@w!e#i$r%d&n*e(s)s.com> wrote in message
news:X6Uqf.2116$dl.1227@fe07.lga...
>
> "Don" <one-if-by-land@concord.com> wrote in message
> news:XITqf.8815$3Z.5591@newsread1.news.atl.earthlink.net...
>
> What do you use for venting of your roofs? Up here, lots of people use
> ridge vents, so the system would need to provide an adequate net free vent
> area.
BTW Paul, do you know if there are any sort of calculations, or requirements
as to the amount of venting that is required?
Frankly, I never thought of this til now.
Normally I spec continuous soffit venting, then on my roof plan I indicate
ridge vents on all peak ridges over 10' long, with the actual ridge vent
being 2' shorter on both ends then the ridge itself. Don't know if that
makes sense the way I said it. As far as I know its never been an issue with
the authorities.
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| RicodJour 2005-12-23, 4:21 pm |
| Don wrote:
> "3D Peruna" <w!h#a$r%o^l&d@w!e#i$r%d&n*e(s)s.com> wrote in message
>
> BTW Paul, do you know if there are any sort of calculations, or requirements
> as to the amount of venting that is required?
> Frankly, I never thought of this til now.
> Normally I spec continuous soffit venting, then on my roof plan I indicate
> ridge vents on all peak ridges over 10' long, with the actual ridge vent
> being 2' shorter on both ends then the ridge itself. Don't know if that
> makes sense the way I said it. As far as I know its never been an issue with
> the authorities.
Rule of thumb is 1 SF vent for every 150 SF of attic. Not sure if
there's another wasy of figuring it for a cathedral ceiling, but I'd
imagine it would be a similar amount.
Sounds like a trip to Building Science's web site is in order.
R
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"RicodJour"> wrote
> Don wrote:
>
> Rule of thumb is 1 SF vent for every 150 SF of attic. Not sure if
> there's another wasy of figuring it for a cathedral ceiling, but I'd
> imagine it would be a similar amount.
>
> Sounds like a trip to Building Science's web site is in order.
Wow.
Looks like my house may be under vented, though its just like every other
crib around here.
Off the top O' my skall, and in basic round numbers, I'm talking about a
60'x54' box with a 24" overhang all around.
That equates to about (60+60+54+54) X 2 = 456 s.f. of soffit vent for about
3200 s.f. of total attic footage.
Or is my math all wrong?
The whole house has trusses so there is attic over the whole house.
I also have about 30' of ridge vent.
My attic gets hot as 4 mf in the summer, prolly in the 130-150 degree range.
I'm gonna pull this up in acad and do a more accurate count on my soffit
footage.
No wonder my fucking light bills are in the $250-$350/mth range.
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| 3D Peruna 2005-12-24, 12:21 am |
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"RicodJour" <ricodjour@worldemail.com> wrote in message
news:1135367140.448581.7780@g49g2000cwa.googlegroups.com...
> Don wrote:
>
> Rule of thumb is 1 SF vent for every 150 SF of attic. Not sure if
> there's another wasy of figuring it for a cathedral ceiling, but I'd
> imagine it would be a similar amount.
>
> Sounds like a trip to Building Science's web site is in order.
>
> R
Somewhere's I have an Excel dealy that calculates the amount of soffit and
vent required based on the net-free vent area. Each product is different.
You plug in the net-free vent area of the product you're using and it tells
you how many lineal feet you need of that particular product for ridge and
soffit.
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| "3D Peruna"> wrote
> Somewhere's I have an Excel dealy that calculates the amount of soffit and
> vent required based on the net-free vent area. Each product is different.
> You plug in the net-free vent area of the product you're using and it
> tells you how many lineal feet you need of that particular product for
> ridge and soffit.
What do you mean by *net free vent area*?
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| RicodJour 2005-12-24, 2:21 am |
| Don wrote:
> "RicodJour"> wrote
>
> Wow.
> Looks like my house may be under vented, though its just like every other
> crib around here.
> Off the top O' my skall, and in basic round numbers, I'm talking about a
> 60'x54' box with a 24" overhang all around.
> That equates to about (60+60+54+54) X 2 = 456 s.f. of soffit vent for about
> 3200 s.f. of total attic footage.
> Or is my math all wrong?
Yes, for various reasons.
-The 1/150 ratio would require 3200/150 SF of vent area.
-The vent area is not the actual area, unless the "vent" is entirely
open and not made of anything.  The net free vent area that 3D
mentioned is the equivalent vent area of any vent system - screens,
louvers and other baffles block air flow, so the net area is actually
substantially lower.
-Your area calculation is slightly high as you used the outer perimeter
instead of the centerline.
> The whole house has trusses so there is attic over the whole house.
> I also have about 30' of ridge vent.
> My attic gets hot as 4 mf in the summer, prolly in the 130-150 degree range.
> I'm gonna pull this up in acad and do a more accurate count on my soffit
> footage.
> No wonder my fucking light bills are in the $250-$350/mth range.
What color is your roofing?
The purpose of ridge venting, and the ratio I mentioned, is primarily
designed for moving moisture and not for cooling the house. The
cooling is an ancillary benefit in the summer. For passive venting the
soffit and ridge areas should be equal.
Cooling an attic in Florida would require substantially more air flow
than passive ridge venting will provide. Thermostatically controlled
powered venting is probably the way to go for your house.
Is your house really 60' x 54'? How do you get natural lighting to the
interior? Lots of skylights? Mirrors a la Sir John Soanes?
http://london-hotels.palhotels.com/...anes-Museum.htm
R
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| RicodJour 2005-12-24, 2:21 am |
| RicodJour wrote:
> Don wrote:
>
> -Your area calculation is slightly high as you used the outer perimeter
> instead of the centerline.
Reverse that - slightly low due to inner perimeter.
If I had some chocolate covered pretzels my blood sugar wouldn't be so
low. ;)
R
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| "RicodJour"> wrote
> Don wrote:
>
> Yes, for various reasons.
> -The 1/150 ratio would require 3200/150 SF of vent area.
> -The vent area is not the actual area, unless the "vent" is entirely
> open and not made of anything. The net free vent area that 3D
> mentioned is the equivalent vent area of any vent system - screens,
> louvers and other baffles block air flow, so the net area is actually
> substantially lower.
> -Your area calculation is slightly high as you used the outer perimeter
> instead of the centerline.
>
>
> What color is your roofing?
Well, Certainteed calls it Alpine White but it looks like light gray to me.
> The purpose of ridge venting, and the ratio I mentioned, is primarily
> designed for moving moisture and not for cooling the house. The
> cooling is an ancillary benefit in the summer. For passive venting the
> soffit and ridge areas should be equal.
>
> Cooling an attic in Florida would require substantially more air flow
> than passive ridge venting will provide. Thermostatically controlled
> powered venting is probably the way to go for your house.
>
> Is your house really 60' x 54'?
Its sort of L-shaped, kinda.
How do you get natural lighting to the
> interior?
More than 1/2 of the south side of the house is glass and its all protected
under a trussed porch.
Plenty of light throughout the house.
Lots of skylights? Mirrors a la Sir John Soanes?
> http://london-hotels.palhotels.com/...anes-Museum.htm
HA!
You can see some of my crib here:
http://tinyurl.com/99egp
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| 3D Peruna 2005-12-24, 12:21 pm |
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"Don" <one-if-by-land@concord.com> wrote in message
news:zJ3rf.10040$Dd2.479@newsread3.news.atl.earthlink.net...
> "3D Peruna"> wrote
>
> What do you mean by *net free vent area*?
If you have a vent, some of the vent is material and the other part is
opening. Let's say your vent is 2" x 12". Not all of the 2"x12" is
open--there's material there. The "net free vent area" is the available
space for air to pass through, which is often as little (or less) than half
the total vent area.
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"3D Peruna" <w!h#a$r%o^l&d@w!e#i$r%d&n*e(s)s.com> wrote in message
news:LMdrf.1545$%c3.191@fe06.lga...
>
> "Don" <one-if-by-land@concord.com> wrote in message
> news:zJ3rf.10040$Dd2.479@newsread3.news.atl.earthlink.net...
>
>
> If you have a vent, some of the vent is material and the other part is
> opening. Let's say your vent is 2" x 12". Not all of the 2"x12" is
> open--there's material there. The "net free vent area" is the available
> space for air to pass through, which is often as little (or less) than
> half the total vent area.
gotcha.
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