Deck weight

NealRomeoGolf

NealRomeoGolf

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Is there a simple formula that would tell me how much weight my deck could hold?
 
NealRomeoGolf said:
Is there a simple formula that would tell me how much weight my deck could hold?
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Depends on what you mean by simple. It can be done with arithmetic. Building codes about how long a span is allowed for 2x4’s, 2X6’s etc. That’ll get you should. But that doesn’t boil it down to ‘could.’ Only way to know that is to build a deck, then pile stuff on it until it breaks
 
From some googling it seems like most codes require a minimum of 50lbs per sq ft. That would mean I've got a 16,000lb capacity. I would need a lot of friends to exceed that.
 
Very loaded questions. If it's built right, the weak point is probably the deck boards themselves, and they'll bend and make noise long before they'll break, if they're in good shape. If it's built wrong, the weak point could easily be the attachment to the house, the joist hangers, or the posts, and they can fail instantly without warning.

I'm a bit of a baby, but I won't go on home decks unless they're close to ground level. I'd sooner ride in the back of a homemade utility trailer.
 
Albany Tom said:
Very loaded questions. If it's built right, the weak point is probably the deck boards themselves, and they'll bend and make noise long before they'll break, if they're in good shape. If it's built wrong, the weak point could easily be the attachment to the house, the joist hangers, or the posts, and they can fail instantly without warning.

I'm a bit of a baby, but I won't go on home decks unless they're close to ground level. I'd sooner ride in the back of a homemade utility trailer.
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Mine has a flight of stairs coming off it. Just stand by the house the whole time and you'll be fine (the property slopes).
 
NealRomeoGolf said:
From some googling it seems like most codes require a minimum of 50lbs per sq ft. That would mean I've got a 16,000lb capacity. I would need a lot of friends to exceed that.
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I bet most people realistically approach their deck capacities with dubious hot tub installations.. which will be around 3,500 lbs once you fill it with 500 gallons of water.. give or take a few hundred pounds, and that won't be evenly spread across the whole deck
 
Tantalum said:
I bet most people realistically approach their deck capacities with dubious hot tub installations.. which will be around 3,500 lbs once you fill it with 500 gallons of water.. give or take a few hundred pounds, and that won't be evenly spread across the whole deck
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I originally set out on this trying to figure out how much I'm giving up by replacing the wood boards with composite, which are heavier. If it can take 50lbs per sq ft, the change in board weight is a rounding error
 
I think you're right, the weight of the boards will be in the noise. I also think composite is a great idea, because they don't rot. But...some used to creep, so they may have shorter span requirements, and could be a problem if you have static loads. That's old info, so if the new ones are fiber reinforced, or better reinforced, it may not be an issue.
 
Albany Tom said:
I think you're right, the weight of the boards will be in the noise. I also think composite is a great idea, because they don't rot. But...some used to creep, so they may have shorter span requirements, and could be a problem if you have static loads. That's old info, so if the new ones are fiber reinforced, or better reinforced, it may not be an issue.
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Many of the early composite boards required 12 on center, which was a problem for remodels. My understanding is the newer boards can do 16, which is what my deck is.
 
NealRomeoGolf said:
Is there a simple formula that would tell me how much weight my deck could hold?
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Unfortunately no.
The decking is probably good. The joists depend on the size, spacing, span and lumber type. The girders depend on the size, span, lumber type and the tributary area they support. The posts are probably good. The piers depend on the girder reactions and the allowable soil bearing.
Sorry for the nonspecific answer but that is how I evaluate decks.
 
NealRomeoGolf said:
Many of the early composite boards required 12 on center, which was a problem for remodels. My understanding is the newer boards can do 16, which is what my deck is.
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I doubt if your talking about collapse. It’s about how much ‘deflection’ is allowed. Yeah, get to much deflection and breakage will eventually follow. Maybe it just gets down to how sturdy it ‘feels’
 
Albany Tom said:
Very loaded questions. If it's built right, the weak point is probably the deck boards themselves, and they'll bend and make noise long before they'll break, if they're in good shape. If it's built wrong, the weak point could easily be the attachment to the house, the joist hangers, or the posts, and they can fail instantly without warning.
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He nailed it. You're screwed.
 
If you have an older design that is lagged into the house for support, I'd avoid putting much on it. After some spectacular failures (usually during parties with a pretty big live load), most codes do not allow this anymore. The deck has to fully support itself and only tied to the house to avoid relative movement.
 
Lots of variables. Foundation type, post type, beams, joists, etc. The enemy of most overloaded decks is movement. If not resistant to movement all the calculated loads mean nothing.
 
flyingron said:
If you have an older design that is lagged into the house for support, I'd avoid putting much on it. After some spectacular failures (usually during parties with a pretty big live load), most codes do not allow this anymore. The deck has to fully support itself and only tied to the house to avoid relative movement.
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Are you sure that's the case? I decided to go read some of the 2018 IRC and it sure seems to say you can still ledger to the house:

"Deck ledgers shall be a minimum 2-inch by 8-inch nominal, pressure-preservative-treated Southern pine...."

It does say that ledgers should not support concentrated loads. My current deck has a ledger connected to the cement foundation of the house and then 3 pillars about 12ish feet from the house. The deck is 21 feet wide and 16 feet out from the house.
 
I don’t know about you guys…for years we had guys measuring their decks here, but now we gotta weight ‘em, too?:rolleyes:
 
NealRomeoGolf said:
Many of the early composite boards required 12 on center, which was a problem for remodels. My understanding is the newer boards can do 16, which is what my deck is.
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I haven't been one any of the newer stuff, but I'd still probably want to have 12" on center if they flex anywhere near what the typical composite decking does.
 
Simple, really:

r5tw11ew87721.jpg
 
I was on a deck 10' in the air years ago that collapsed during a party. It was pretty bad, fire and life squads, police the works. I got hurt by a beer keg crushing me, luckily it was not the full size refrigerator or the many plates of glass/mirrors that were stacked against the wall on the deck that I could of got hit by. Nobody died, several went to the hospital and stupid me didn't go. Which made me responsible for the medical bills later.

It was nailed to the house and not bolted, and pulled loose. It was a big deck, we did hear squeaks before it let go.
Have not partied on a deck since. Not a deck fan, imagine that.
 
When we bought our house, the deck ledger was nailed to the house with 16d nails. Idiots. The posts were sitting directly on the ground, no pier blocks. I rebuilt it using mostly new material. The posts were fine once I shortened them for the piers, and the main support beams were still sound.

The new deck wasn’t permitted or inspected, which I think was only fair since the original sure as hell hadn’t been. Actually since I reused the posts I hear referred to it as a repair job… same data plate, new fuselage. :)
 
SoonerAviator said:
I haven't been one any of the newer stuff, but I'd still probably want to have 12" on center if they flex anywhere near what the typical composite decking does.
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Cross blocking between the joists will make the deck much more rigid than just putting closer joists. Cross blocking ties the joists together so when one tries to flex the others help carry the load.
 
I’ve got a distant relative who designed and built his own second-floor deck and put a big box store hot tub on it. From what I understand the collapse was spectacular, and all these years later the wreckage is still tight where it fell.
 
kmacht said:
Cross blocking between the joists will make the deck much more rigid than just putting closer joists. Cross blocking ties the joists together so when one tries to flex the others help carry the load.
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Sure. However, the problem isn't about the joists/support structure not being rigid. The problem is the span between joists being too long for composite decking which allows them to sag in between joists. They may make thicker composite decking now that is more rigid, but the couple of decks I've been on with 16" spacing used a composite 5/4 board and you could feel it flex underneath your feet, especially in hot weather/direct sunlight.
 
NealRomeoGolf said:
Are you sure that's the case? I decided to go read some of the 2018 IRC and it sure seems to say you can still ledger to the house:

"Deck ledgers shall be a minimum 2-inch by 8-inch nominal, pressure-preservative-treated Southern pine...."

It does say that ledgers should not support concentrated loads. My current deck has a ledger connected to the cement foundation of the house and then 3 pillars about 12ish feet from the house. The deck is 21 feet wide and 16 feet out from the house.
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Around here (also 2018 IRC), you attach the ledger with lag bolts, and the lag bolts are put in on a staggered pattern, and there need to be 1" spacers installed between the rim joist and the ledger to allow for water drainage or flashing needs to be installed properly. The problem that existed for a long time was where decks were nailed to the house, and the nails would pull out and allow the deck to collapse.
 
I'm having my entire deck redone. They did repairs when I bought the house but missed several things. Piers that have sunk sideways into the ground, non-pressure-treated beams that are no longer wood and "exterior" rated fasteners. Where I am if it's not stainless you'll be hosed in a few years, and I was.
Most of the boards came off with a light tap from the hammer, the ones that weren't already fully loose.

deck.jpg
That beam on the outside edge has several spots where you lightly tap it and it just disintegrates.
In a few months I should have a nice after photo.
 
chartbundle said:
I'm having my entire deck redone. They did repairs when I bought the house but missed several things. Piers that have sunk sideways into the ground, non-pressure-treated beams that are no longer wood and "exterior" rated fasteners. Where I am if it's not stainless you'll be hosed in a few years, and I was.
Most of the boards came off with a light tap from the hammer, the ones that weren't already fully loose.

View attachment 112838
That beam on the outside edge has several spots where you lightly tap it and it just disintegrates.
In a few months I should have a nice after photo.
Click to expand...
When I removed the staircase, some of the stringers were in the process of disintegrating. Glad I decided to do the rebuild. I've done almost all of this myself except I paid my friend (who is a carpenter) to have one of his guys do the new stringers. They also reinforced the piers and the connection of the ledger board. I started laying boards down for the stairs on Saturday. After that just need to finish the stair railings and the fasica. It has been an education.
 
Building a deck for a customer in the shop now. The steel the engineer spec'd is insane! You could park an excavator on the thing. Right now it weighs around 4,200 lbs.

IMG_20221205_171108899.jpg
 
When I built my deck, I oversized everything. Do if the deck design books/programs said a given part could be a 2x4, I used a 2x6. And it said use a 2x6, I used a 2x8. I would have to check if I did 12 or 16 inch centers.

It not a high deck, but it is freestanding.

And the footers are not going anywhere. It turns the load of concrete they send was for another job that got cancelled after the truck was on the way. My footers are 8,000 psi, fiber reinforced, concrete. :D
 
Two normal sized people per square meter or 2 Italian mother-in-laws for the entire deck.
I'll be going now.. Bye
 
Don't forget the dynamic loads.
 
So I started this thread a year ago yesterday. Here was the deck journey (in 2 posts)...

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