Roof Top Deck Rail Posts Leaking

by Clarence Powell
(Greensboro, NC)

I have a deck built on top of a flat roof. The roof leaks heavily around the 4x4 posts securing the deck to the roof. I have tried tar and roof tape around the posts, but it still leaks. Can you give me some advise on this please...

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Oct 05, 2011
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Floating decks are less prone to leaking
by: Editor-Rich Bergman

When you have tried pretty much everything to stop leaking around these posts which protrude into your roof space your options become limited. Trying to guess where water is entering is a frustrating mind game.

If I were confronted with this problem I would be now looking at a complete re-roofing job to be absolutely sure the problem has been fixed. But this is your most expensive worst case option.

A tar or torch on roof technique well wrapped around those posts should have solved the problem. Since it hasn't I wonder if the job was done meticulously. It just doesn't sound right. What about other areas of the roof deck. Could they be leaking?

This is why I am highly cautious of recommending people insert wood guardrail posts into the framing of the roof on a roof top deck. It just raises the stakes very high.

Once you go that route you have to rely 100% on the integrity of the waterproofing job around the posts which is not easy because of all the corners and angles. But you also have to make sure the entire roof surface is well waterproofed against the any other parts of the house if this applies and certainly be sure the surface can handle the weight and or foot traffic if it is the final walking surface.

Floating decks are a much safer option provided they too are also securely attached to the roof as well. This can be done by using steel anchoring bars or connectors that bolt on to the roof joists and also certain locations along the floating deck framing.

The deck also should should sit on padding under the joists to ensure the joists can air dry always and don't damage the waterproofing membrane. The deck joists ideally should run perpendicular to the roof joists but this means you must make sure the deck joists sit off the roof surface so rain water can freely run down the roof.

The beauty of this system is that the deck railing can be either set into the joists using traditional fastening techniques or if you want a lower profile deck you can use a surface mounted rail system like aluminum systems or my Titan Post Anchor system for wood posts.

The Titan Post Anchor has been tested against the US residential building code testing regime (AC273) in September 2011 and has handily exceeded these standards which are set at 2.5x above the design loads of the code. You can learn more here.

So you do have options...

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