Deck over space

[Eurob]

So I guess hands on experience backed by photos -- including few of the steps -- is the road to go .

Some efforts -- long term benefit -- are well worth doing .

 

[Eurob]

We don't have lab working conditions ......... 10 C temperatures -- exterior conditions -- have a hard impact on your skin in the long run . I cannot touch any pantyhose thow .... LOL

 

[Sponsor]

 

[Jadnashua]

It seems that some people forget where all of the products that they use come from...testing in the labs where they verify that they actually work. But, the biggest problem is people thinking they know better than hundreds of engineers and lots of field tests to work out the bugs. A scientific test is one that is repeatable to you can verify the thing under test. It's not good enough that it works one time, which may be a fluke, it has to work all the time when used as designed. Changing design, changes the possible outcomes, and you're on your own. It might work, it might not. You may spend a huge amount more for something that would have worked just fine done in a different manner. Thing is, often, you'll never know.

 

[Koa]

Aren't you trapping moisture in the ply once you install your waterproofing? Where does the moisture go that was absorbed by the ply from the thinset? Do you experience freezing weather where you are located?

When I did a roof top deck I was careful to make sure everything was as dry as could be below the waterproofing membrane. I used treated ply that was then kiln dried to keep moisture levels down.

 

[Vegas_sparky]

We had a wet summer in Utah. I have a small exterior alcove leading to my front door. It gets hammered when it rains. My wife said there's a leak in the area, evidenced by water damage on my basement office ceiling, which is directly below. John, I'm gonna send you an email this evening, and hope you can help me with some details for a solution.

 

[Vegas_sparky]

I didn't see that. I'll look for it now.

 

[Eurob]

"The deck is approx 50 feet across, and varies in depth between about 18 and 24 feet. It is just about 900 sq ft in total area. The structure is two offset layers of 3/4" exterior plywood, glued and screwed together, over engineered joists (I-joists) and beams (LVLs). The design provides a minimum of L/720 deflection with joists 12" and 16" on center, depending upon length. This structure is now built, and it is an extremely solid and stiff structure."*

I didn't see any mention of the structural supports -- pillars and footing work -- . It is all good to get it -- deflection -- up to the standards , but it is not all . Solid and stiff with or WITHOUT vertical movement ..... wonder how was that accomplished .

"I will be using Noble Deck membrane for waterproofing, even though the deck is not constructed over occupied space, which I have already purchased. I have inside and outside corners from Noble, and will be attaching the membrane using their EXT product. Noble specifies two installation approaches for plywood decks: either an exterior grade CBU or a fairly thick mortar bed. I pretty much have to use the CBU option to minimize the thickness of the deck, and National Gypsum's PermaBase is the only cement board I've found where the manufacturer is ok using it outside as a backer for flooring installations."*

The connection in between the vertical structural walls and horizontal deck floor is one of the most critical points , among others .

"Since I chose NOT to do the typical interior two-layer plywood approach of allowing each sheet of plywood to move independently in both layers (maybe a mistake, but I'm there now), I need to determine the best way to allow for expansion and contraction of the structure under the three layers that I have not yet installed: the PermaBase, the Noble Deck and the porcelain tile. I've spoken with the manufacturers, but I'm not yet comfortable if there would be value in having soft joints in the CBU layer (and if so, how many), whether using soft joints in the tile layer alone every 8-10' (and around the perimeter) is sufficient, whether there may be something else I can do at this point, etc."*

2 layers of 3/4 plywood would be a minimal requirement before the 3 layers -- mentioned -- will be installed . This is not an interior -- controlled -- environment .

You can debate in having controlled joints through out the assembly -- 10' to 15 ' in all directions in sun exposed areas -- or just having them through out the rigid layers -- cbu and the tile -- . There is specific diagram to be respected for going over with the waterproofing and crack isolation membranes .

I would just do soft joints in the tile layer , but if you expect vertical movement , then control joints should be carried through out the assembly .

 

[Vegas_sparky]

I would go shiny side down, as long as accumulated condensation won't be a problem.

 

[JohnfrWhipple]

After a long cold snap the weather outside is warming up.

Time to get back to the deck job.

Drove by the North Van deck last week and still no framing done. Looks like that job is pushing off till spring.

 

[Vegas_sparky]

I read about you humping all that material upstairs, and had to take a nap.