Is 4.8 kPa too much for a single family house deck? 3

[AlexWong122]

I have one big deck in a single family house on the main floor and one balcony on the second floor. Both are the similar size 40' x 15'. The National Building Code of Canada specifies a live load of 4.8 kPa for a deck (intended to be a assembly area), which is 500 kg/m2. Isn't that too much for just a single family house, especially for a 2nd floor balcony?

Appreciate your thoughts.

 

[BAretired]

I don't think so. The owner of a house with two 600 square foot decks probably likes to throw big parties. They should be designed as assembly areas.

BA

 

[skeletron]

4.8kPa (100psf) is totally reasonable for a balcony. It's an assembly area. A big deck like that will be used to it's fullest potential (ie. not just a couple of hammocks and a BBQ).

>>>>QUASI-RELATED>>>>>>

https://globalnews.ca/news/5186260/...ast-15-to-hospital-serious-injuries-reported/

Not sure what the cause of collapse here. But the point is that balconies need some conscious design and have often been underestimated by designers.

 

[MIStructE_IRE]

My view is always the same as BA’s - the richer the client the bigger the party.

Decks/balconies have a tendency to attract concentrated groups at parties too.. 4.8 kPa sounds good to me.

Consider he’ll also probably want 1m x 1m plant pots..

 

[istruct1980]

this might help you

 

[HouseBoy]

Since you asked for opinions....

In my experience, a deck that is well designed and detailed (structurally) for 50 psf is well suited for the intended use.

The "problem" I see does not have to do with the difference between 50 psf and 100 psf design loads. A deck that is poorly designed (usually it's the details) for 100 psf is not going to be better than a deck that is well designed and detailed for 50 psf.

Just my 2cents

 

[Tomfh]

In my experience, a deck that is well designed and detailed (structurally) for 50 psf is well suited for the intended use.

Agree.

The "problem" I see does not have to do with the difference between 50 psf and 100 psf design loads. A deck that is poorly designed (usually it's the details) for 100 psf is not going to be better than a deck that is well designed and detailed for 50 psf.

Agree too. Though I'm not sure how many of those decks which fall off were designed by engineers!



At the end of the day if his code says 4.8kPa, then that's the answer..

 

[Canuck65]

As long as the house meets the requirements to be considered under Part 9 of the NBCC, then the minimum design live load for a single family residential deck is LL = 40 psf or the design snow load, whichever is greater. The LL = 40 psf is the same minimum load that the interior floors would be designed to support. However, this is the minimum load and quite often engineering judgment must be considered. If this is the type of client who may want to load up the deck with planters and such, or host large parties, then I agree that 100 psf would be reasonable and likely a $$$ upgrade that the client is willing to pay for.

 

[Settingsun]

Looking at the picture posted by Eugaulas, I'd have said around 4kPa. Canuck65 says the balcony load is the same as the interior but balconies are an attraction IMO so could be expected to see a higher peak load. As for trying to judge the owner: houses get sold; children grow into teenagers and throw parties; a quick web search yielded a balcony collapse at a gathering of those notorious Tupperware salespeople etc.

 

[Ron247]

this might help you

That pic is a big help. I plan to send it to Clients and Architects in the future when they question my choice of design loads if that is OK with you.

 

[BAretired]

In addition to floor load, design of the handrail, balisters, posts and their connections to the deck must be designed to resist lateral loads as specified in the code. This is an item which, in my experience, is often inadequate on balustrades around wood decks for private residences. It is particularly important in the case of 40' long balustrades at second floor level.




BA

 

[JoshPlumSE]

I don't think it's unreasonable to design for 100psf. However, I tend to walk back the LL deflection limit to something like L/240 instead of L/360.

As with most failures, my impression is that the dramatic deck failures we've seen recently are more connection failures or corrosion / water damage than they are member failures. I wonder if it would be a more rational idea to design to 50psf for members, but 100psf for connections. Any experts on the subject care to comment?

 

[Ron247]

I too would not be too worried about deflection. A little excessive deflection may reduce the tendency to crowd too close. I might design deflection for 60 psf and full load for 80 to a 100. Excessive deflection in this case is not damaging any drywall or causing the plumbing to drain backwards.

 

[oldrunner]

The biggest boo boo is connection details and waterproofing. Within the last few years, water was the culprit of the Oakland deck failure killing a number of students and the other failure in Folsom that killed one student. Both cases hidden wood rot. The State of California issued some new requirements concerning decks. Over the years many failures of "parties" and decks going down.