Rotten cantilevered balcony beam tails.

[Prestressed Guy]

I was called in by the AHJ to investigate the soundness (lack thereof) of some structural element in a tenant improvement in my town. As a part of the improvements, all of the interior finishes were removed down to the structural bones which provided a very good look into how the structure is holding up.
It is a Mid-Century Modern commercial building which was very popular in this town in the late 50's and early sixties so the bones are at least 60 years old. It has the typical exposed post and beam construction of the type and most of it is in surprisingly good condition. The exception is a line of 4x12 beams that extend through one exterior wall and cantilever out 40" and form a walkway around that side of the building. The beams appear to be Doug Fir which is by far the most common wood used in this area.
The walkway appears to have been well sealed for its entire life except for along the railing edge where there have been obvious long-term leaks that have allowed fungal rot to eat away at the ends. Before I was called in the contractor built a new railing by sistering some new wood to the good portion of the beams to support the new solid railing wall.
No effort was made to remove the existing decay which given that this is exterior in the Pacific Northwest will not be what you would call a dry condition.
My thought is to mechanically remove the rotted wood to back to sound wood and then treat the ends and sides with something like Sansin BoracolSansin Boracol or Impel Rods Link to kill any fungal spores.
After treating the fungal infestation, the remaining beam ends would have new ends sistered to one or both sides similar to what the contractor has done but with proper size, back span, connections then it all be painted to minimize moisture in the wood.
Any thoughts or suggestions.

 

[dhengr]

Prestressed Guy:
I would look very closely at the ext. wall penetration area (the canti. brg. point/area) too. That, and the exposed ends of the 4x12s are notorious locations for rot if those areas are not perfectly flashed and maintained, to keep water off and out of them. Doug. Fir doesn’t treat worth a darn but I would still apply a penetrating preservative anyplace you can, to cut ends and surfaces, etc., plus your rot killer products. A 2x sister on each side should probably be o.k., but it must take the whole railing and short wall loading well back into good wood, with fairly high connection reactions at your cut end of the 4x12s. I would at least butt a bot. & maybe top 2x4 in the cut-off space/length to make your sisters a box beam and dress the bot. up a bit. On deck joists and beams, I like to flash the tops with 30# ice and water guard type roofing materials, a self sticking and self healing flashing of sorts. Let it hang over the edges 3/8" or so, forming a drip edge a bit away from the side of the beam. There are some rolled roofing products, self sticking and self healing tapes, made just for this purpose, and for various joist and beam widths. You can put a top and end cap flashing, with drip edges, on those beams too. Maybe you should flash the whole length of that walkway, under the wall pl. and out and down the ends of the beams. Of course, the ends of the beams will tend to suck up the water, but the beam penetrations at the exterior walls is another place I’ve often seen real water damage. This is always a bad detail and difficult to flash well.

 

[Prestressed Guy]

Thanks for the comments.
Adding blocking to the end of the cutoff beam was already in my plans but I forgot to mention it. The top surface of the walkway had already been reflashed, sealed with a membrane and wearing surface before the AHJ flanged it and had me called in so we really would prefer to do everything from the bottom. The beams have been sounded with a hammer on the inside and outside of the exterior wall bearing and are sound with no sign of rot or any signs of water intrusion in that region. Everything is open and looks pretty good except for the last few inches of these beam ends.
One interesting thing is that this repair will only need to last for about 10-years because a planned redevelopment will cause it to be removed at that time. The current improvement is to provide a temporary home for a business until its new location can be designed and built nearby.

 

[LittleInch]

You'r not seriously telling anyone that the walkway should be being used given the level of destruction and rot of the main beam are you?

Those new supports aren't worth the wood that has been used as they connect into what looks like the last vestige of the beam that is left.

If this is only for 10 years I would seriously look at removing the whole thing as I don't think you'll have enough "sound wood" left to sister some bigger joints to. IMHO.

There are far too many instances of balcony failure on this site resulting in serious injury and death. People do have a tendency to stop and lean on the outer rail whilst enjoying the scenery or leaning back on it whilst talking to others inside or on the balcony / walkway itself.

For anyone who didn't look at the attachment this is it.

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Also: If you get a response it's polite to respond to it.

 

[XR250]

I would cut them clear back to the wall for aesthetic purposes - even if sound wood exists beyond that.
Run the new wood back in 8 ft or so and let it bear on the exterior wall so the connection loads are manageable.

 

[jerseyshore]

Holy shit, there is no way I would even consider using that old wood for anything after seeing this. Balconies are the few things that actually collapse in residential construction and never something I mess around with. UC Berkeley being a tragic example of what can happen. And in general I don't like scabbing on wood to the end for load bearing purposes.

I would install either new treated joists to replace the old, or some treated parallam beams at a bigger spacing so that you can do more infill framing in between.

 

[phamENG]

My recommendation to clients for these is to a) install posts at the edge of the balcony and reframe without the cantilever or b) cut it back to the wall, patch the finishes, and install a "Juliet Balcony" at the door. Notice that neither of those options involve installing a new cantilever.

 

[Prestressed Guy]

Thanks to all who have commented. This is a long post but trying to respond to all comments at one go. Also know that at this point, I am working on a Letter of Findings to the building owner outlining recommendations and repairs based on my non-destructive investigation. None of this is based on calculations or final design decisions which will require further selective demolition and removal of rotted materials do to clean health wood structure.

You'r not seriously telling anyone that the walkway should be being used given the level of destruction and rot of the main beam are you?

Those new supports aren't worth the wood that has been used as they connect into what looks like the last vestige of the beam that is left.

I bit of clearity is needed.

The joist in the near ground has the worst damage but the photo makes the admittedly bad damage appear significantly worse than it is in real life. The black spot below and 5" to the right of the end of new wood is peeled paint showing the previous layer of black paint below. Probing this spot with an awl shows good sound wood below. The large void down the mid-height of the beam extending from the end back about 12" toward the wall appears to be at a natural check in the end of the beam which allowed water to penetrate that distance and allow the fungal rot to advance about a foot into the mid-height region. The wood above this check is sound to just short of where the paint ends. The rot below the check extends back a few inches farther. All of the damage is confined to this last 12" of the beam based on sounding with a hammer and probing with an awl.

The new 2x6's that are screwed to the side of the beam were done by the contractor and are not adequate in size or connection and will be removed. That said, the railing wall above is solid and resists the required outward 200lb point load. I went up on the walkway above and laterally pressed between the wall and top of railing and there was very little lateral deflection. [Much less then I expected actually. My plan was to demonstrate to the owner that the connection was too weak. Fortunately, he did not notice my "test" so I didn't need to explain why it was bad when it seemed "good"]

I would cut them clear back to the wall for aesthetic purposes - even if sound wood exists beyond that.
Run the new wood back in 8 ft or so and let it bear on the exterior wall so the connection loads are manageable.

The preference is to avoid removal of the cantilever and replacing with new cantilevered sisters if possible due to how the beams are detailed into the wall and for interior esthetics. The interior structure is exposed in a MCM building. The rot is confined to the last 12" at most of the 40" total beam projection. That leaves 28" of good wood to connect a pair of new sistered 2x12 boards with a 12" projection. The gravity moment in this connection is quite small. The greater load is from the horizontal force at the top of the railing. This will be handled by the T_C couple to the post where the 2x12's lap the base of the post. The gap from the cut back end of the beam to the 4x4 post will get infill blocking to fill the gap solid.

Holy shit, there is no way I would even consider using that old wood for anything after seeing this.

As I said, the damage is not as bad as it appears in the photos but that said, at this time I have only completed a non-destructive investigation and in the process of writing the Letter of Findings with recommendations for possible repairs. The owner will be presented with several options for corrective measures and final design will be based on actual conditions after the rotted wood has been removed to see the actual extent of damage. If the damage is greater than what can now be found, the repair will involve either new cantilevered beams or a post and beam supported walkway.

My recommendation to clients for these is to a) install posts at the edge of the balcony and reframe without the cantilever or b) cut it back to the wall, patch the finishes, and install a "Juliet Balcony" at the door. Notice that neither of those options involve installing a new cantilever.

If the damage found when removing the rotted wood down to clean wood is too great for repair, Option a) is certainly the simplest and what I would recommend to the owner. Option b) is not possible because this is a walkway which provides access to the ground as an exterior fire-escape.

 

[LittleInch]

Thanks for coming back to us and explaining it more. I'm sure you can see our thoughts based on only one photo whereas you, of course have seen more and felt it etc.

The devil will be when the paint and beams are fully exposed and cut back.

The logic of a fire escape built from wood and relying on wood beams inside the building for support escapes me, but I'm sure this has been considered somewhere in the design review....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.