Inabox85
Well-known member
I did plywood at our old house in a section of the attic. I never put anything super heavy in there.
Attic in Garage
- Thread starter MJBaldwin
- Start date
I would ask for 40 psf bottom chord live loading.
10 psf is light, very light. 1/2" plywood is about 2psf, so that leaves 8psf. as reference thats about 1.5" depth of water. Find a 12x12 pan, put about 1.5" of water in it, and you get a feel for whats your capacity.
I believe the standard used is 10 minutes for typical residential trusses built with plates. Ten minutes from their initial exposure to fire that can start failing.
You can do that, my response was to the other member asking about the plates and trusses used in typical residential trusses.
Drywall is a barrier but doesn't keep a place from burning down.
driftpin
Well-known member
You're right-there in the hunt on that one. I believe the copy I have of Francis Brannigan's Building Construction for the Fire Service says, "...as-little as eight minutes before structural failure." Brannigan advocated for building placards to announce to arriving fire suppression units that the construction was light-truss constriction, because of the risk of catastrophic collapse in the event of a well-seated structure fire. He also didn't think much of light bar-joist construction either, for the same reason.
Here is a text for the fire service on building collapse by another world-wide respected authority, Vincent Dunn:
http://www.montgomerycountymd.gov/f...ollapse_of_burning_buildings_201606121459.pdf
Documentation of truss failure responsible for the deaths of two Memphis firefighters:
https://www.usfa.fema.gov/downloads/pdf/publications/tr-069.pdf
Unfortunately, there are many-more like this.
I am a career firefighter/paramedic, now retired, but still qualified as-such, and a Fire Service Instructor III, plans examiner, and Lifesafety Code Inspector. My career began 43 years-ago.
Here is a text for the fire service on building collapse by another world-wide respected authority, Vincent Dunn:
http://www.montgomerycountymd.gov/f...ollapse_of_burning_buildings_201606121459.pdf
Documentation of truss failure responsible for the deaths of two Memphis firefighters:
https://www.usfa.fema.gov/downloads/pdf/publications/tr-069.pdf
Unfortunately, there are many-more like this.
I am a career firefighter/paramedic, now retired, but still qualified as-such, and a Fire Service Instructor III, plans examiner, and Lifesafety Code Inspector. My career began 43 years-ago.
Vintage Veloce
Well-known member
This is your truss? 0 pounds live load and 10 pounds dead load? This means it is safe for a skinny cat to walk up there, that it.
Send this to a truss engineer (I suggested one earlier in this thread) and ask him what to do.
lakeroadster
Well-known member
^^^ Yeah... not really ^^^
5 is better than 10, 15 would be better.
MJBaldwin it all depends on if you install drywall on the ceiling, if you install insulation and how much those weigh, pounds per square feet.
Do the numbers then see if the left over capacity is enough for you. It's pretty simple math.
As far as drywall for fire code, if you drywall the wall all the way up to the roof deck that isolates the garage from the home. Then you can do whatever you want with the ceiling in the garage. You won't be required to do anything for a ceiling.
My barn uses trusses rated for 15 psf for the lower chord. I built a loft and use it for light storage, but I am very mindful of what I place up there and where I put everything.
5 is better than 10, 15 would be better.
MJBaldwin it all depends on if you install drywall on the ceiling, if you install insulation and how much those weigh, pounds per square feet.
Do the numbers then see if the left over capacity is enough for you. It's pretty simple math.
As far as drywall for fire code, if you drywall the wall all the way up to the roof deck that isolates the garage from the home. Then you can do whatever you want with the ceiling in the garage. You won't be required to do anything for a ceiling.
My barn uses trusses rated for 15 psf for the lower chord. I built a loft and use it for light storage, but I am very mindful of what I place up there and where I put everything.
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LifeLongWNYer
Well-known member
Thanks guys, especially NUTTSGT for the reply, and understood about the sheetrock. That will probably so up, eventually, so I'm covered there. I did, coincidentally talk with the lumber yard today and asked my contact about the plywood vs: gang nails matter, he said he will contact the truss builder, but he suspects they are "set up for" gang nails and the plywood and galvanized nail method may no longer be possible.
I'd like to ask a question about the numbers in the truss design which was posted by MJBaldwin. The document sent to me by MY truss guy ( via the lumber yard ), with a couple of differences in that left hand column, is about the same. ( It appears they use either the same software, or the same format ) Mine has:
TCLL: 38.5
Snow: 50.0
TCDL: 10.0
BCDL: 0, and
BCDL: 10.0
The estimator told me that the statement "This truss has been designed for a live load of 20.0 psi on the bottom chord in all areas where a rectangle 3-6-0 tall by 2-0-0 wide will fit between the chord and any other members" PLUS another one "Bottom chord live load (40.0 psi) and additional chord dead load (5.0 psi) applied only to room. 16-18"
I guess I don't even know enough about this to be dangerous. Which of those numbers tells me what I can store in an attic, and what about the weight of the sheetrock on the bottom, and the plywood on the top? I guess the people who deal with trusses all the time know this, but why isn't there a legend to explain the abbreviations?
.
I'd like to ask a question about the numbers in the truss design which was posted by MJBaldwin. The document sent to me by MY truss guy ( via the lumber yard ), with a couple of differences in that left hand column, is about the same. ( It appears they use either the same software, or the same format ) Mine has:
TCLL: 38.5
Snow: 50.0
TCDL: 10.0
BCDL: 0, and
BCDL: 10.0
The estimator told me that the statement "This truss has been designed for a live load of 20.0 psi on the bottom chord in all areas where a rectangle 3-6-0 tall by 2-0-0 wide will fit between the chord and any other members" PLUS another one "Bottom chord live load (40.0 psi) and additional chord dead load (5.0 psi) applied only to room. 16-18"
I guess I don't even know enough about this to be dangerous. Which of those numbers tells me what I can store in an attic, and what about the weight of the sheetrock on the bottom, and the plywood on the top? I guess the people who deal with trusses all the time know this, but why isn't there a legend to explain the abbreviations?
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lakeroadster
Well-known member
LifeLongWNYer: You're not hijacking anything - we are all trying to learn here.
Its hard when you have one guy telling you that 10 will not even hold a cat although another guy saying that 15 he stores light objects up there. I am sure they have some sort of a safety factor built into it although I don't really want to rely on that. This is a standard 2-story home. That being said this is the way the construction industry is going. Trying to get things cheaper and manufactured items some work better I think and others not so much.
I think I will check with my builder.
Its hard when you have one guy telling you that 10 will not even hold a cat although another guy saying that 15 he stores light objects up there. I am sure they have some sort of a safety factor built into it although I don't really want to rely on that. This is a standard 2-story home. That being said this is the way the construction industry is going. Trying to get things cheaper and manufactured items some work better I think and others not so much.
I think I will check with my builder.
lakeroadster
Well-known member
It's not hard at all. Only you know what you plan to store up there.
Weigh the items and their size, do the math, and you will have your answer.
Let's say you go with the advice of GMCGarage and use 40 psf and you want a 10' x 10' storage area with your ladder going right into the middle of. That area will hold 4,000 lbs.
Let's say you go with what you already know, 10 psf and that same 10' x 10' storage area but no ceiling or insulation in the garage. That will hold 1,000 lbs. (That's one fat dead wet cat Vintage Veloce)
What's realistic for you in your world?
For what you've previously described... 1,000 lbs should be more than enough.
Vintage Veloce
Well-known member
I may be over cautious, because the garage attic at my old house had been "reinforced" by the owner and was sagging really badly, more than a 3 or 4 inches in the middle. It creaked and groaned and I was concerned goin up there. Then at my new house, the old garage there had a sagging roof, and we had to replace the lower cords with 2x6 and add supports to the ridgeboard and other upper pieces under the roof.
In out new building's attic I spent the $200 with a truss engineer (listed in the thread above) for about an hour of his time to really design what we wanted. The extra cost of minimal to upgrade to 2x6 trusses, space them in a custom way (less than 24" except where the stairway is placed) and to maximize the space and to support the attic stairway.
I'll note we are taking book boxes out of storage. They are 10"x10"x16" and full, weigh about 38 pounds each. So that is about the limit of a 40 PSF truss. I wouldn't put a stack of these in a 40 PSF attic, Personally I'd be sure to spread them out.
In out new building's attic I spent the $200 with a truss engineer (listed in the thread above) for about an hour of his time to really design what we wanted. The extra cost of minimal to upgrade to 2x6 trusses, space them in a custom way (less than 24" except where the stairway is placed) and to maximize the space and to support the attic stairway.
I'll note we are taking book boxes out of storage. They are 10"x10"x16" and full, weigh about 38 pounds each. So that is about the limit of a 40 PSF truss. I wouldn't put a stack of these in a 40 PSF attic, Personally I'd be sure to spread them out.
lakeroadster
Well-known member
Weights of Building Materials – Pounds Per Square Foot [PSF]
____________________________________
Curious.... what did you end up using for the bottom chord loading, psf?
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Vintage Veloce
Well-known member
My design was checked for 200# per truss for the stairs, plus 40 PSF total load in the 9’ wide attic area. Note also that my truss is worse case design at 28.5” on-center, with the trusses at 1’-4” and 2’ on center not carrying as much load.
The wide spacing was to accommodate the stairway, and that is only in one spot. Most of the trusses are on 24" centers, so that effectively makes things more robust than the calcs show.
These are still pretty basic trusses made of 2x6, 21' long, 6/12 pitch. 13 trusses (9 attic plus 2 end trusses) cost me $1870, delivered, here in expensive San Diego.
The wide spacing was to accommodate the stairway, and that is only in one spot. Most of the trusses are on 24" centers, so that effectively makes things more robust than the calcs show.
These are still pretty basic trusses made of 2x6, 21' long, 6/12 pitch. 13 trusses (9 attic plus 2 end trusses) cost me $1870, delivered, here in expensive San Diego.
nolimits76
Well-known member
Thanks for the link.
Hey OP, notice the link states to include 1.5 PSF for misc items as the minimum (towards bottom of second page in bold).
Gyp board/sheetrock = 2.75 PSF
11/32” or 3/8" Plywood – OSB(3)1.0 - 1.2 PSF
15/32” or 1/2" Plywood - OSB(3)1.4 - 1.7 PSF
19/32” or 5/8" Plywood - OSB(3)1.8 - 2.1 PSF
23/32” or 3/4" Plywood - OSB(3)2.2 - 2.5 PSF
3" of insulation x .04 PSF = .12 PSF
Just for ease....
2.75 PSF gyp board + 2 PSF plywood + .12 PSF insulation + 1.5 PSF misc = 6.37 PSF total in building materials
That leaves you 3.63 PSF for storage. Or 363# for a perfectly distributed fat cat in a 10' x 10' space.
texas123
Well-known member
You could build a storage shed like I did. Collect the lumber from the builders "trash piles" & get paint, tools & other stuff on craigslist. It would only cost a few hundred bucks & be able to support anything.
https://www.garagejournal.com/forum/showthread.php?t=386711
https://www.garagejournal.com/forum/showthread.php?t=386711
Attachments
lakeroadster
Well-known member
Thanks for the link.
Hey OP, notice the link states to include 1.5 PSF for misc items as the minimum (towards bottom of second page in bold).
Gyp board/sheetrock = 2.75 PSF
11/32” or 3/8" Plywood – OSB(3)1.0 - 1.2 PSF
15/32” or 1/2" Plywood - OSB(3)1.4 - 1.7 PSF
19/32” or 5/8" Plywood - OSB(3)1.8 - 2.1 PSF
23/32” or 3/4" Plywood - OSB(3)2.2 - 2.5 PSF
3" of insulation x .04 PSF = .12 PSF
Just for ease....
2.75 PSF gyp board + 2 PSF plywood + .12 PSF insulation + 1.5 PSF misc = 6.37 PSF total in building materials
That leaves you 3.63 PSF for storage. Or 363# for a perfectly distributed fat cat in a 10' x 10' space.
Nolimits.. Your numbers are bloated, just like the cat.
Your using 5/8" Gypsum and 5/8" plywood? And what's with the 1.5 psf misc?
Use 1/2" drywall for ceiling: 2.2 psf
Use 7/16" OSB as decking: 1.4 psf
Insulation.......................: 0.12 psf
Total weight = 2.2 + 1.4 + 0.12 = 3.72 psf
10 psf - 3.72 psf = 6.28 psf for your stuff.
That's 628 lbs of boxes and ****...
OP: Don't use a pull down ladder.. you need 6 psf just to support the ladder.
53 lbs ladder ***'y that measure 24" x 54": 53 / ((24*54)/144) = 5.88 psf
Build the shed in the backyard or some shelves in the garage... the attic storage is inconvenient, dirty and hotter than the hinges of hell. You ever try carrying boxes that are full of stuff up one of those pull down ladders? Now if it were just empty boxes.. sure.
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Shed is in the plans for the future but I want this stuff up high and out of the way. Also a side note to that comment I dont know what kind of builders you have around there but the ones around my new house are very lean when it comes to materials used. They dont throw as much as one would think.
nolimits76
Well-known member
Nolimits.. Your numbers are bloated, just like the cat.
Your using 5/8" Gypsum and 5/8" plywood? And what's with the 1.5 psf misc?
Use 1/2" drywall for ceiling: 2.2 psf
Use 7/16" OSB as decking: 1.4 psf
Insulation.......................: 0.12 psf
Total weight = 2.2 + 1.4 + 0.12 = 3.72 psf
10 psf - 3.72 psf = 6.28 psf for your stuff.
That's 628 lbs of boxes and ****...
OP: Don't use a pull down ladder.. you need 6 psf just to support the ladder.
53 lbs ladder ***'y that measure 24" x 54": 53 / ((24*54)/144) = 5.88 psf
Build the shed in the backyard or some shelves in the garage... the attic storage is inconvenient, dirty and hotter than the hinges of hell. You ever try carrying boxes that are full of stuff up one of those pull down ladders? Now if it were just empty boxes.. sure.
LOL, good call on the cat and my numbers.
By the way, you are spot on about the attic storage. I'm not sure I'd put as much work & effort into creating a storage space I know I will cuss time after time later on, but each to his own.
In two of the houses I've owned, I had attic access from an upstairs and that was the cat's meow. Those access ladders are just meant to piss people off I'm pretty sure. Currently i'm renting but when I build/buy again, I will seriously consider installing an attic lift/winch system.
One final thought....even at 628# of capacity that is for an EVENLY distributed load. Not to mention the weight of the OP should he decide to walk up there. Hopefully he's skinnier than these damn 1,000#, 600# and 300# cats we've been discussing.