Deck expansion detail questions

[DoubleStud]

So I have this deck remodel where we will extend the deck another 4 ft. It will be a complete tear down but we will reuse the piers. Currently, the beam at the piers are flush with the joists. I am planning to use a steel beam below the joists (continuous span) and cantilever the joists. It has not been confirmed yet but we are expecting the columns are made of CMU wrapped with stone veneer. I need some inputs from you guys:
1. Is it easy to cut down the CMU column to exact height? Or does it have to be cut at the cmu joint? I am thinking to cut the column to 1" below the new steel beam and the beam will just sit directly on it (plus shim and grout). The other option would be to cut well below the steel beam and add HSS column in between. Just trying to simplify things.
2. For outdoor steel beam deck application, do you typically still use a nailer (pressure treated) plate on top of steel beam and you toe nail the joists to it? Or do you drill holes on top flange and screw it directly to the joists/blocking? Just thinking about aesthetic and performance against rotting.

 

[phamENG]

Well the piers should be grouted, so where it gets cut won't really matter. Bearing the steel directly on the CMU isn't a problem as long as bearing checks, which it should for this. Just make sure the steel connection is stable.

As for connecting the joists....make sure you consider uplift. This looks like you're on the top of a mountain with a view, which means it's exposed and potentially subject to higher loading from the terrain. Uplift on your 4' overhang is likely. A nailer works and is likely the best way to go, but be mindful of cross grain bending from your uplift connections and be work with the architect to flash the nailer and joists to prevent any areas where water can get trapped between pieces of lumber and sit there. But generally speaking yes, I'd have them toe nail the joists, block the joists, and then tie them down to a nailer. Nailer would be secured with bolts and plate washers large enough to prevent or at least mitigate the negative effects of cross grain bending.

 

[jerseyshore]

Cutting down the CMU shouldn't be a problem. Let the GC figure that out. I'm assuming they are hollow currently so it'll give you the opportunity to fill them solid as well.

I use a top flange nailer on 99% of steel beam to wood situations. Unless they just can't afford to lose that 1.5", I want a nailer there. Easy for H2.5A ties too.

 

[DoubleStud]

phamENG, thanks for the reply. When you said flashing, did you mean tape covering the nailer?

 

[Eng16080]

I am planning to use a steel beam below the joists

I imagine you have a good reason for using steel, but if a wood beam can work, that would be my preference.

Is it easy to cut down the CMU column to exact height? Or does it have to be cut at the cmu joint?

I'm not a mason, but based on some limited experience working with concrete, assuming you have a 16"x16" cmu pier, cutting it to a certain height shouldn't be too difficult, especially if the cmu cores are hollow. I would have no problem doing this myself with a circular saw and angle grinder using diamond blades. I don't know if I would necessarily call it "easy," but it's definitely doable. Cutting to "exact" height may be difficult, but I would overcut slightly and then grout back up, which is what it sounds like your plan is anyway. Overall, I think the more difficult part will be removing the stone veneer.

For outdoor steel beam deck application, do you typically still use a nailer (pressure treated) plate on top of steel beam and you toe nail the joists to it?

My detail for this condition is normally a double PT plate bolted to the galvanized steel beam top flange. I would use galvanized hurricane ties to connect each joist to the nailer, but toe nailing probably isn't the end of the world (I'm just not a big fan). Make sure there's solid blocking between the joists above the beam as well. If the double PT nailer is a problem for aesthetics, then perhaps you'll need to go with the second option of providing holes for each joist through the top flange, but that seems like a lot of work/coordination. Also, since the beam should be galvanized, the holes should be shop drilled prior to galvanizing, as opposed to drilled on site.