How to anchor a deck to a flat rooftop?

Looking into building a deck on the rooftop of my apartment. The roof has recently been re-done (gravel). I am wondering how to anchor the deck to the roof without compromising waterproofing of the roof.

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May 31, 2010
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A couple of thoughts on roof top decks
by: Editor - Rich Bergman

Whether you want to penetrate the roofing membrane or not you will have to build a floating deck that rests on sleepers of some sort. A number of issues will arise that you should take into consideration.

First off just double check that the roof joists are capable of hold a load such as a deck and the likely number of people and things on it. You may have to ask a builder, engineer or inspector to confirm this for you but its number one on the list.

If it can handle the load then you will want to be sure that you align any sleepers at perendicular angles to the direction of the joists to ensure the loading is safely done. You could use 4x4s, patio stones are a number of other similar materials to rest your decking structure on top. But you should make is heavy enough that it won't lift up in severe winds and that it will be strong enough for a railing system of whatever sort you choose to use to connect to.

A slight slope of 2% (1/4" per foot) would be advisable if it can be done properly and look nice. This will increase the life of the decking by encouraging proper water drainage.

As far as anchoring the deck to the roof is concerned, I think about the only option that is realistic is to pierce the membrane to connect into the roof structure itself. But if you do so you must do so in consultation with a reputable roofing specialist who is confident about being able to reseal and reapply a new seal in that area. That is crucial or you will have a disaster on your hands.

I can't imagine any other way of anchoring that deck to the roof from what you have described without breaking the membrane. If there is a roofing specialist among our visitors, share your knowledge please.

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Building a rooftop deck over a roof with a small pitch

by Sharon
(Salt Lake City)

I want to add a garage to the front of my house and add a second story over it.

From the second story over the garage I would like to extend a deck out over my house to make good use of the view.

The roof has a slight pitch, Is that possible?

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Apr 29, 2011
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A roof deck is possible
by: Editor-Rich Bergman

Its certainly possible to incorporate a roof deck over a new garage extension. However you must follow all guidelines for a safe and high performing roof deck. You should have an architect or an engineer review of provide you with planning details.

Some of the things they are going to recommend are:

Roof slope of at least 2% (1/4" for every 12")
Load rated roof joists for snow load on a horizontal roof or consideration for the live and dead loads
Proper waterproofing and a decision of whether the deck will be part of the waterproofing membrane or a sleeper deck system
Connecting any sleeper deck securely to the roof itself

Roof decks area a great idea. But because they serve dual purposes, protecting the structure from weather and also acting as a deck, extra care has to be taken in planning and executing all construction details.

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Deck over sloped rooftop

by Casey
(St. Joseph, Michigan)





I am looking to build a small deck over my front porch (6' x 25' - see pictures), accessed by a spiral staircase on the left side of my house, in order to get a better view of Lake Michigan.

Main Problem: The roof slopes down about 2.4" per foot (it drops 16" in the 80" that it comes away from my house). If I attached a ledger board to the house, the deck would have about a 24" tall faceplate that went across the length of my house between the gutter on my front porch and the flooring of the deck (which I think may look ridiculous, and would like to minimize). I considered tapering the joists somehow, but I'm not sure how that'd work.

Secondary Problems:

1. How to support the front two corners of the deck (posts to the ground, only one of which I could easily dig a hole) or have posts that are attached to the roof (not sure if that is to code, and I would like to avoid attaching too many things to the roof).

2. Boot pipe vents for plumbing - could work around them

3. Is the front porch strong enough? I am not too worried because what I'd like to put up isn't that big, and it'd have at most 4 people on it at a time. I had a lot more than that on it when I reroofed a few years back.

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