Collapsed porch for Cleveland Double 1

[ASGStruct]

Hello,

I have a project for a second story porch roof collapse. No surprise given every home in this area has severe deflection problems with either the upper level porch floor or roof.

In re-designing the porch, I have a setup with two exterior 6x6 posts that will set onto the existing brick piers ~8 from the home. I'll reinforce the 2nd level porch floor with a new LVL beam, since it's already deflecting and has a junk 2" post at midspan.

The posts will extend to the and roof level and support two 3-ply LVL beams that will tie back into the home at existing beam pockets. These beams will pick up 4 pre-engineered roof trusses spanning 25' each. With an end reaction of ~1.8 kips, I am wondering if this is an appropriate design.

The wall structure is ~12 thick with brick masonry veneer, ~3 5/8" and presumably 6"-8" wood studs. I don't believe that it is multi-wythe construction, but I was unable to verify this. If so, then I will use the City of Chicago porch design details for beam pockets.

My question is whether placing a reaction this large near the ends of the home is a good idea. I am unsure how they will frame the beams into the wall and be able to get positive bearing via the existing beam pockets. Can you only face mount the beams, since there is a ribbon board likly in place.

I was thinking that maybe running another 3-ply LVL header up high from post-to-post out front and then framing back to the house at 16" c/c would be a better way of picking up the roof.

If anyone has any ideas about what the likely construction of the exterior wall is, and whether I should try to support the roof continually across the face of the home instead of at only two locations, I thank you in advance.
It's possible that the 1.8 kips reaction is not that severe a load for an exterior wall, but I don't know if there are any defects that may reduce the capacity.

Thank you

 

[Ron]

It is doubtful that you could get uniform support of the trusses across the front of the house....the loads would still be concentrated near the ends of the proposed "rim" board.

1.8 kips is not that large of a load, assuming you can support it on something besides the brick veneer. I think you should verify the wall construction before you proceed with the design. It could be either wood frame or concrete masonry, based on the dimensions you gave. More likely to be wood framed with 6" studs, a 2" gap, and brick.

The house has been performing for many years as originally designed. The need to replace the roof and porch now is presumably related to deterioration, not inadequate structural design. If so, you're only putting back what was there, with current code provisions added.

Don't forget to accommodate waterproofing in your design.

 

[msquared48]

I would be concerned with using an untreated LVL, especially if it has to bear on brick and sit in a confined space subject to moisture.

Personally, I would lean more to a 4X or 6X member of a species that was pressure-treatable. Not sure what is readily available in Chicago though.

Frankly, I would use all PT material here for the deck structure.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[csd72]

I wouldnt be so certain that it is not multi wythe, it looks like there could be somecross bonding in those walls.

Could potentailly be a solid double brick wall with drywall on the inside. Can you lift the tarp and see what is inside the previous beam support holes?

As far as support is concerned, the corner is generally the strongest place to put the load.

 

[Ron]

Au contrare, csd72...corners carry the lightest gravity load in a building...less influence area.

 

[ASGStruct]

Thank you again for the great information. The wall is indeed brick veneer with the void and 6" studs. I've also got the moisture problems accounted for with the LVL in contact with brick masonry or concrete. Hopefully, the 87 year old woman will have her porch back in the near future...

 

[druminman]

I've worked on some condo projects where "protected" LVL beams have completely failed after only 4-5 years. I'll never use them again for porch or deck construction. There are companies making glue-lams from pressure treated, kiln dried material that I specify when a solid sawn timber or multiple 2x12s won't do the trick.

Also, even in a treatable species, most mills won't warranty pressure treatment on any member more than 4" thick.

 

[ASGStruct]

Hello,

The building department came back with a few comments. I've attached a jpeg version of the file, which should show the drawing set on engineering.com.

Here is what they are requesting:

1.Connection between upper porch floor joists to dwelling
2.Connection between lower ceiling joists to dwelling 3.Connection between these two and the glulam beam
4.Framing details of 2nd floor porch skirt

I was hoping to stay away from reconstructing the existing floor joists, ceiling joists, and skirt, since they aren't badly deteriorated, but I hear from the G.C. that everything might be at odd centers up to 30", a la the porch roof that collapsed! So Id like to detail this existing 2'-0" deep void by framing over and into the side of the Glulam, but I have no idea what they used as beam pockets or ledgers. Is it possible that only the top floor joists were framed into the home and the ceiling dropped down? I considered keeping the existing joists at 30" and adding a new one between each, but it all turns out messy for me.

I am looking for a detail to salvage the existing or start from scratch, and which would be preferred.

Thank you all for your help in advance.

 

[BAretired]

Given the history of these structures in that area, it is not surprising that the building authority is asking for these four items.

You have to allow the contractor to do enough preliminary work to allow you to properly inspect the existing conditions. For the G.C. to forward information on existing conditions to the engineer as stated in your boxed note is not satisfactory.

Any determination of existing conditions and the required remedy must be made by you.

BA