Tie-in to Existing Elevated Floor 1

[TRAK.Structural]

What's the standard approach/detailing for supporting a new elevated floor off an existing exterior wall that supports an existing elevated level? It would seem that the existing wall could be opened up to thread new floor joists in between existing floor members, but I think the wall sheathing would have to then be replaced and potentially with additional connectors/straps to justify continuity of the shear transfer down to ground from lateral loads. Another approach could be a ledger type design which would eliminate disturbance of wall sheathing but that just feels less secure than using the standard joist bearing on top of walls approach. Anyone done this before?

 

[TRAK.Structural]

No takers here?

 

[phamENG]

Missed it yesterday.

Both are potentially viable, but what's going on down on the first floor? If there's a beam or header down there, are you going to overstress it by adding this floor load? If it's a solid wall, I'd just do a ledger. But you need to follow the load paths (gravity and lateral) all the way to the foundation. Are you familiar with the IEBC and its rules for structural components during an alteration or addition? (That is assuming the IEBC is adopted in your jurisdiction and applies to houses.)

 

[ANE91]

Are you familiar with the IEBC and its rules for structural components during an alteration or addition? (That is assuming the IEBC is adopted in your jurisdiction and applies to houses.)

We’ve hired people straight from the world of home additions/remodels, and they’ve never heard of the IEBC. Aren’t there explicit exceptions for most residences, as you allude? I’ve read that code cover-to-cover multiple times.

I don’t like ledgers. Contractors often miss the studs, even though the sheathing nails are right there. Besides, there’s probably a quarter-board of sheathing at the floor platform, anyway, and removing it allows you the opportunity to make sure there’s no funny business going on with the top plate. If that lower wall ends up needing more studs, then you’re going to be taking off the sheathing, anyway.

 

[TRAK.Structural]

Missed it yesterday.

Both are potentially viable, but what's going on down on the first floor? If there's a beam or header down there, are you going to overstress it by adding this floor load? If it's a solid wall, I'd just do a ledger. But you need to follow the load paths (gravity and lateral) all the way to the foundation. Are you familiar with the IEBC and its rules for structural components during an alteration or addition? (That is assuming the IEBC is adopted in your jurisdiction and applies to houses.)

Wall is solid below.

Yes, for sure need to check wall framing and foundations for increased load. For lateral I would just plan to make sure the new structure can stand on it's own so there is no increased lateral on the existing.

We’ve hired people straight from the world of home additions/remodels, and they’ve never heard of the IEBC. Aren’t there explicit exceptions for most residences, as you allude? I’ve read that code cover-to-cover multiple times.

I don’t like ledgers. Contractors often miss the studs, even though the sheathing nails are right there. Besides, there’s probably a quarter-board of sheathing at the floor platform, anyway, and removing it allows you the opportunity to make sure there’s no funny business going on with the top plate. If that lower wall ends up needing more studs, then you’re going to be taking off the sheeting, anyway.

I am not huge on ledgers either, even though that's the way all decks are framed in my area. Anchoring through the rim/band to hold up a new floor just isn't as comfy as direct bearing on the top plate.

 

[phamENG]

Aren’t there explicit exceptions for most residences, as you allude?

Depends on the jurisdiction.

Here in Virginia, the IRC isn't the code, the Virginia Residential Code is. The VRC is an edited version of the IRC. Similarly, the IEBC is edited and renamed VEBC, and the IBC is edited and renamed the VCC (Virginia Construction Code). Chapter 1 is completely replaced in the VRC, and includes the following:

2021 VRC 103.1.1 Virginia Existing Building Code - Part II of the Virginia Uniform Statewide Building Code, also known as the “Virginia Existing Building Code,” or the “VEBC” is applicable to construction and rehabilitation activities in existing buildings and structures, as those terms are defined in the VEBC, except where specifically addressed in the VCC.

In other words, unless the VRC specifically identifies requirements for an existing structure, the VEBC applies.

Now, the IRC does have Apendix AJ, Existing Buildings and Structures. In Virginia, this is edited with a heading that says "This appendix is informative and is not part of the code." But many other jurisdictions may use it as enforceable code.

 

[phamENG]

Ledgers are common place. Use heavy duty structural screws rather than nails, and hang the joists from them. Cutting into the sheathing will cause all sorts of headaches.