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Exterior deck king truss flashing question

GeorgeH3's picture


I had a basic covered deck structure (he built the framing, I'm finishing it up) put on the back of my house. The outer gable of the roof is supported by a king truss made out of non-PT dimensional lumber.

I'm going to cover the sides and bottoms of the truss members with stained cedar to match the rest of my deck. After I install the cedar, I want to cap the top sides of each member with aluminum flashing. I'm fine with the bottom horizontal beam but I'm confused as to how to flash the elbow/armpit/crook area between the vertical member and the two angled middle members. Is there a standard method for flashing that kind of intersection/valley so that water won't get in under my cedar cladding.

Let me know if you have any questions and reference the url for the pic for the king truss and hopefully you'll see what I mean.


Also, should I cover the raw non-PT wood of the truss with tyvek or some other material before installing the cedar and flashing?

Thanks in advance,


p.s. just to head off some anticipated questions...

- I'm cladding in cedar because the rest of my deck is done in cedar and it's what my wife wants ('nuff said, right?)

- I'm going to use black aluminum flashing to match my black ballusters and LV lights

- I can't flash the entire truss with aluminum because my wife likes the look of a wooden structure

questions (post #215551, reply #1 of 8)

This may be due to the angle of the photo, but it sure likes like that "lower chord"/beam is deflecting quite a lot. Did this thing get engineered? It looks like a substantial portion of that roof is resting on point in the middle of the beam right where there is deflection. Also, is that really just resting 1.5" on top of the post? And it looks like it is just two dimensional boards run, separated by the diagonals and some blocking?

It is due to the photo...the (post #215551, reply #2 of 8)

It is due to the photo...the deck design was drawn up by an architect. The truss beams are built-up using three 2x boards in layers. So the lower beam is "woven" with the side beams in a stepped fashion...does that make sense? (Like herringbone pattern when looking at the corner from above)

Also the lower horizontal beam is not sagging at this point. I have wondered about what you're talking about though and have wanted to get a strutural engineer out to look at it to make sure it is ok before I wrap it all in cedar.

Any input on the proper way to lap the flashing in the valleys on top of the beams in the truss?

Thanks, George

George (post #215551, reply #3 of 8)

Is there a ridge "beam" ?

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


I hate to judge just based on (post #215551, reply #4 of 8)

I hate to judge just based on one picture, but no way in hell does that structure look anywhere near adequate to me.


Where are you located?  Do you know what your loading requirements are?

Ron (post #215551, reply #5 of 8)

I have built quite a bit and taken thousands of photos.

what I see in the picture is not good and not camera distortion.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Update on structural comments! (post #215551, reply #6 of 8)

So I took all of your comments to heart and finally found a structural engineer to come out and inspect my deck (not an easy thing to do surprisingly). He went over the whole deck and especially the truss and said it's good. The township inspector has also approved it. Now, personally I don't know - I'm not an architect or structural engineer but that's what they said.

So anyhow...back to the original question - anyone know how I can clad/flash this thing? I temporarily wrapped it all in tyvek to keep the rain off of it but I have to do something more permanent and have decided to wrap it in black aluminum flashing. But am unsure of the best way to flash the beam intersections.



George (post #215551, reply #7 of 8)

I tried the link for you photos and it said, not here anymore.  Dropbox?

hard to give an opinion but, flashing usually goes from bottom up.  With each succeeding layer lapping over the one below.

The angled intersections will require you to deal with a bit of a nightmare.  Repost the picture and maybe ........


hope me you have a brake.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


Since you're going to cover (post #215551, reply #8 of 8)

Since you're going to cover the whole things I'd get some Grace Vycor and warapthe whole thing. 

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.