Tips/Techniques Deck structural question - simple

[phaxtris]

These are your 3 ideas ? Detail 2 is the best, both 1 & 3 add a lot of twisting force to the existing joist, probably ok, but not great. 1 would likely need carriage through bolts to keep that stack together, the other 2 options would be fine with standard .120 hot dipped framing nails

You should also put a membrane on the top of the stack, water will collect on the top and work it's way between, rotting things out over time. They do sell a product specifically for putting on the top of deck joists, I don't recall the name of it

 

[Susquatch]

View attachment 67520

These are your 3 ideas ? Detail 2 is the best, both 1 & 3 add a lot of twisting force to the existing joist, probably ok, but not great. 1 would likely need carriage through bolts to keep that stack together, the other 2 options would be fine with standard .120 hot dipped framing nails

You should also put a membrane on the top of the stack, water will collect on the top and work it's way between, rotting things out over time. They do sell a product specifically for putting on the top of deck joists, I don't recall the name of it

Agree with you, but would say that 2 might not be wide enough.

I'd also add that 3 needs the bolts.

Option 1 sucks as drawn. I wouldn't do that myself no matter how much $ it saved. It is a future problem waiting to happen.

A 4th option is to get rid of the decorative laterals. They compromise the deck structural design too much for the aesthetic value.

An option discussed but not drawn is the narrower laterals with a 3 board joist. I like that one too.

@slow-poke - I especially support phaxtris's suggestion to add a sealer/membrane on top of any stacked beam. I think is a badly overlooked but extremely important part of any deck construction. Your deck boards are synthetic but the joists are not.

 

[slow-poke]

View attachment 67520

These are your 3 ideas ? Detail 2 is the best, both 1 & 3 add a lot of twisting force to the existing joist, probably ok, but not great. 1 would likely need carriage through bolts to keep that stack together, the other 2 options would be fine with standard .120 hot dipped framing nails

You should also put a membrane on the top of the stack, water will collect on the top and work it's way between, rotting things out over time. They do sell a product specifically for putting on the top of deck joists, I don't recall the name of it

Thanks for the tip on covering the joists. This will be my third Trex deck and I'm sure it will outlive the structure. I'm not sure the structure will outlive me, but the tape should help.

I purchased the Trex from Ottawa Deck Depot, I have to say that the service and delivery have been excellent. They supplied 10 rolls of tape for the tops of the joists. As well as all the hardware. Nowadays I prefer to give my $ to preferably smaller businesses especially home grown. I actually sent a RFQ to Home Depot, crickets from them and the Trex is already here.

Yesterday the gods were looking after me. The Trex was sitting on skids in my driveway, I have a bad back and moving 1800 ft to the backyard and up the steps was beyond what I want to do. I'm navel gazing over the Trex and I see two young guys walking down the street that I don't recognize. So I chat them up, turns out they are from Mexico and working on one of the houses being built down the street. So I ask them if they know anyone willing to move the Trex. A quick negotiation later they agreed to come by after work and move the entire pile. They worked their a**es off and moved it all safely and quickly. I fed them when they were done. Real win-win. They are willing to provide more help as needed, so my project just got turbocharged.

 

[Susquatch]

@slow-poke - Does your municipality have deck bylaws? We have not discussed that here, but some municipalities have deck by-laws. If so, you will want to run your design past them before you start work.

 

[slow-poke]

BTW,

Thanks to everyone for chiming in.

Until Susquatch pointed out the cantilevered long boards adjacent to the decretive boards I had not thought about it, too focused on fastening the decretive board. Obviously I would have dealt with it but better to be aware now.

SWMBO likes the accent board, so guess what?

Okay... tea time is over back to work

 

[phaxtris]

Agree with you, but would say that 2 might not be wide enough.

I'd also add that 3 needs the bolts.

Option 1 sucks as drawn. I wouldn't do that myself no matter how much $ it saved. It is a future problem waiting to happen.

A 4th option is to get rid of the decorative laterals. They compromise the deck structural design too much for the aesthetic value.

An option discussed but not drawn is the narrower laterals with a 3 board joist. I like that one too.

@slow-poke - I especially support phaxtris's suggestion to add a sealer/membrane on top of any stacked beam. I think is a badly overlooked but extremely important part of any deck construction. Your deck boards are synthetic but the joists are not.

yes 1 sucks, i wouldn't do it either, but it was mentioned thats why i drew it

2 is the same width as 3, they are both 4 ply, there is 2 existing joists drawn, i recall @slow-poke saying he had some double joists, that is what is depicted, it may be hard to see if your looking on a phone. I dont think bolts are required for 3, loaded up with 3 1/4 or 3 1/2 .120 framing nails and you would have a time prying that apart with a burke bar, we can agree to disagree on that. There could also be the option of pl and nails, thats still less expensive than a pile of grk's.

Edit, sorry, your right 2 is 4 and 3 is 5, giving 6" vs 7.5", yes may not be wide enough

im guessing the perpendicular boards are there to deal with the overall length, although staggering the butts would give the same results and hide any length problems, it would still likely require some blocking. But im guessing he wants to reduce the cutting and waste, that trex is hugely expensive.

Thanks for the tip on covering the joists. This will be my third Trex deck and I'm sure it will outlive the structure. I'm not sure the structure will outlive me, but the tape should help.

I purchased the Trex from Ottawa Deck Depot, I have to say that the service and delivery have been excellent. They supplied 10 rolls of tape for the tops of the joists. As well as all the hardware. Nowadays I prefer to give my $ to preferably smaller businesses especially home grown. I actually sent a RFQ to Home Depot, crickets from them and the Trex is already here.

Yesterday the gods were looking after me. The Trex was sitting on skids in my driveway, I have a bad back and moving 1800 ft to the backyard and up the steps was beyond what I want to do. I'm navel gazing over the Trex and I see two young guys walking down the street that I don't recognize. So I chat them up, turns out they are from Mexico and working on one of the houses being built down the street. So I ask them if they know anyone willing to move the Trex. A quick negotiation later they agreed to come by after work and move the entire pile. They worked their a**es off and moved it all safely and quickly. I fed them when they were done. Real win-win. They are willing to provide more help as needed, so my project just got turbocharged.

I have never installed trex or any composite decking, I have built or rebuilt close to 10 conventional wooden decks over the years, but never that stuff, when I lived in Manitoba everyone was to cheap, and out here in Alberta the few that i do know who sprung for a composite deck complained about the expansion and contraction, and with the darker shades in the intense sun that southern Alberta get the deck got so hot you couldn't walk on it with bare feet. So with the decks ive built here, i continue to use 5/4 p/t decking.

 

[Johnwa]

I would do option 1, but rather than 2 2x4s I’d use a 4x4. In addition to fastening it to the joist, a hanger at each end will provide vertical support and reduce twisting. You only need to support the end of a 12” cantilever so my gut tells me that twisting won’t be a problem.