Deck Design - Notching of Wood Piles

[JoelTXCive]

I am reviewing an architect's plans for a duel-level wood deck. Half the deck is at one elevation and then there is a step down to a lower elevation sitting area.

The deck is supported by 10" diameter wood piles and the proposed design has the lower level supporting beams (DBL 2x8) notched into the piling.

The pile continues upward and the upper level's support beam is then notched into it. (see attached diagram)

The pile has plenty of axial capacity for the given loading, but I am concerned about lateral stability since there is a region where a full 6" of material has been removed from a 10" column.

What do you think? Maybe there is an alternative way we can do this connection?

 

[hokie66]

A 2" deep notch should be enough. That leaves 6" nominal meat in the pile.

 

[msquared48]

I agree.

Mike McCann, PE, SE (WA)

 

[dhengr]

JoelTXCive:
I was going to say notch into the 10" dia. pile 2.5" on each side. This provides a little more bearing area for the two outer 2x10 beam members, and still leaves about a 5"x9" solid post member btwn. the two beams. I would cover the top surface of the pile and the two beams with peal-n-stick flashing to keep water out of the entire joint and out of the beam splices over the length of the beams. Take a look at the AF&PA Design Guide #6, Design for Code Acceptance, “Prescriptive Residential Wood Deck Construction Guide,” for some good general deck design and construction info.

 

[KootK]

I don't think that it's a serious structural issue but I do worry that you'll loose that "P" shaped chunk at the top of the pile. Could you just stop the pile at the undeside of the upper beam?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[msquared48]

Koot makes a good point. I initially had the same plthought. I would uconsider using a deeper beam on the right so you could install two bolts through the pile and both beams.

Mike McCann, PE, SE (WA)

 

[hokie66]

I agree with dhengr that 2.5" notches are a good choice. And I agree with KootK that the bit at the top on the right is useless, so I would just split that off. But the roughly 5" side post section should continue to the top. Both beams should be through bolted to the posts, and then retightened after shrinkage takes place.

 

[dik]

Detail is fine as is, with the 2=1/2" notch. Cut the pile 1/2"-1" short of the top joists for shrinkage of the joists if on top of the pile. A couple of HDG lag screws and you're done. Maybe leave a slight gap between the deck planks for shrinkage/expansion.

Dik

 

[JoelTXCive]

Thank you all for the input. This has been very helpful.

The plan going forward is:

• Change the beams to DBL 2x12 due to some loading changes
• Drop the beam on the right so that there is no 'overlap region'
• Reduce the notch size
• Bolt both beams

Thank you again for helping the lowly EIT.