Post Anchor Question - InspectionNews

Jim Robinson · #1 (**permalink**) 07-02-2008, 02:51 PM

This is for my house for a project coming this fall. I have a three story house, and on top of the existing second story roof there is a small walk out section onto the roof, accessible through a door in the third floor wall. I want to make it nicer by adding a deck and railing, along with a roof over the deck.

The question I've been working on is regarding the corner post for the deck roof. The other side will be supported by a third floor wall, so I only need one post. I'd like to keep from penetrating the roof membrane if possible. Have any of you seen a post on a walk out roof like this, and if so what did they do to flash it to keep water from running down the post and into the wall area? I'd prefer to just use a standard post base, but that won't have any uplift resistance. We rarely get any high winds here, so I wouldn't be worried about that, but I don't think my local building inspector will allow it. He's probably going to want something anchoring the upper section to the lower part. I drew a diagram if it helps to visualize it.

Jim Robinson · #2 (**permalink**) 07-02-2008, 02:55 PM

Scan was too large. By the way, how do you guys get those nice looking jpeg and pdf images uploaded?

Steven Turetsky · #3 (**permalink**) 07-02-2008, 04:43 PM

Hi Jim,

How are you attaching the sleepers... the entire deck... to the structure?

My point is, if it is attached securly, all you would have to do is notch the 6x6 and bolt it to the inside of the sleepers before you install the decking. Add some nailers to the post to give yourself a place to attach the decking.

I also assume you will be installing a railing. If the railing is attached to the house, it will also give lateral support to the post.

I have never built a deck like you describe, but I've built a few docks and a number of decks. I like bolts as compared to nails.

Jerry Peck · #4 (**permalink**) 07-02-2008, 05:16 PM

I don't know about where you are, but down here ... that post would be required to be strapped to the structure below, such as through the roof to that wall - which in turn would have been required to be strapped down (via a continuous load path) to the foundation.

James Duffin · #5 (**permalink**) 07-02-2008, 06:03 PM

I did a house the other day that had added a deck to the roof. Their method could help you not make the same mistakes!

Jim Robinson · #6 (**permalink**) 07-02-2008, 08:27 PM

Normally, the sleepers are only fastened with roofing cement to the roofing material. I haven't actually seen a permitted roof deck that didn't have the perimeter walls stuccoed and boxed in. I don't really want to do that (box in the whole deck with a stucco wall), and I'm expecting the AHJ to tell me that the post should be tied into the framing.

The question is have any of you seen a post tied into the framing or through the roof, and if so what did they do to seal the opening at the roof to keep it from leaking. The perimeter movement of the post isn't a problem, since it will be tied in with the railing and the roof above it. The only real structural issue would be uplift. I was hoping that perhaps someone had designed a special anchor that was easier to flash than a standard set up. I guess I may be able to strap the end of the decking down to the fascia pretty easily if I planned for it ahead of time. If I put a roof over the deck, I was not going to put gutters on the far end of the roof, since very little water would actually drain off of the deck.

Rick Sabatino · #7 (**permalink**) 07-07-2008, 08:34 AM

I have seen posts through the roof before, but very few don't leak. I was at one home where they did not know they leaked until the insulation was so heavy the family room ceiling came down one night with a big boom.
I also don't think you want to use roofing cement under each sleeper. The wood and cement will move at different rates with temperature fluctuations. I would add either some 1 ply, or rubber roofing under each sleeper. Also fasten each sleeper to the house at the rear with steel brackets.
Is the deck as wide as the roof below? Can you come down the out side and fasten into the walls below to get your uplift security?

Jerry Peck · #8 (**permalink**) 07-07-2008, 09:53 AM

My understanding is that they are only "sleepers" if not securely and permanently attached to the structure/roof.

Such as when laid in a bed of plastic roof cement.

Once permanently secured/attached, they are no longer "sleepers", they are part of the structure.

If one is concerned about the movement differential between the wood and the plastic roof cement (which is why the plastic roof cement is used, to allow for that movement), then you could put down a bed of plastic roof cement, metal flashing or modified flashing (must be compatible with the plastic roof cement), then another bed of plastic roof cement with the wood "sleepers" on that.

That would allow for an isolation layer between the wood and the roofing, however, it now creates the same problem between the roofing and the metal flashing isolation layer, etc.

Markus Keller · #9 (**permalink**) 07-07-2008, 10:18 AM

I'll let everyone else debate the attachment question. Personally I would run a post from grade up with shoulder cuts and bolts.
However, if you want to do what is in your diagram, I say use a regular post base with a bolt and simpson nails.
I've built numerous roof decks similar to this and have developed my own sealing method that seals and holds.
Lots of guys burn rubber around the post and caulk it. Some guys burn rubber around the post and put small pieces of term bar on top. Good methods but they all leave the seam positive to the vertical plane and susceptible to leaks.
I use my router to cut out a 1/4" deep x 3/4" wide channel all the way around the post, then tack nail and burn the rubber on and caulk. Now the rubber (or your flashing material) is negative to the vertical plane reducing leak potential.
I haven't had any call-backs in years.