Deck over flat roof on House Boat: penetrations needed.

[Sans Absol]

Howdy. First post here, but excited about the threads I've read so far. I've always learned a lot from JLC.

Client would like a rooftop deck on their houseboat. Roof is curved at about 1.5/12 pitch average. As it is a houseboat and thus subject to unpredictable wake and 3D motion, I need to secure the posts to structure: sleepers or unsecured pedestals won't suffice.

My roofing sub is going to take a look, as the roof needs redone before the deck can go up, and he'd mentioned the use of steel piers to prevent wicking of water down through wooden posts and into the living area. Walls are 2x4 with double plates, I'll be spanning 13.5', and posts will only be 18" high at rooflines, maximum. I have searched but found no solutions to this situation, as most posts are reccommended to be large (4.5" O.D. or larger, as shown here: http://www.decks.com/deckbuilding/St...k_Post_Columns)

Are there standard steel piers available to fit 2 x 4 walls? What should I be looking for as feedback from my roofing sub? Will I need to have steel posts fabricated for me?

Thanks for your help, looking forward to hearing it all!

[Chuck Kiser]

Re: Deck over flat roof on House Boat: penetrations needed.

Check with the local codes to ensure this is allowed. If it is, your best bet is to query other house boat owners with decks to see how they solved your problem. With all the boat shops in Seattle, I know somebody has already figured this out. Good Luck.

[dgbldr]

Re: Deck over flat roof on House Boat: penetrations needed.

Contact member Lavrans here. He is familiar with your climate, boats, and decks.

[Lavrans]

Re: Deck over flat roof on House Boat: penetrations needed.

Where are you moored?
What is the roofing?
How bi can the posts be?

Steel would be good- use a good through hull sealant, then bring the roofing membrane up the post, then the wood post fits over that as a counter-flashing. Option 2 is to mount the posts to the roof eave I there is sufficient structure. And a half dozen other usable methods, depending on structure & materials.

[Dick Hackbarth]

Re: Deck over flat roof on House Boat: penetrations needed.

And, this all assumes that a house boat structure, probably built about like an 8x18 house trailer, can take the second story loads, both vertical and lateral, at four concentrated locations. Don’t forget handrails and their post loads, and getting this all down to the hull, which may or may not be adequate for those concentrated loads. Is this arrangement a boat stability problem? You better study all the existing construction details to see how this will really work before they plan the deck warming party.

[Sans Absol]

Re: Deck over flat roof on House Boat: penetrations needed.

Where are you moored? 2727 Fairview Ave E. Hamlin docks
What is the roofing? Torch down with hot mop and embedded granules. Not sure what replacement roofing will be.
How bi can the posts be? It is 2x4 construction with 2x4 top plates.

Steel would be good- use a good through hull sealant, then bring the roofing membrane up the post, then the wood post fits over that as a counter-flashing. Option 2 is to mount the posts to the roof eave I there is sufficient structure. And a half dozen other usable methods, depending on structure & materials.

I don't think there is sufficient structure for the roof eave approach.

If you are local and are interested in checking it out, I'd love your input, especially as your website shows you do great work. I'm meeting the owner and roofer tomorrow morning to discuss options, take measurements and photos and review. Plus, I have access to the site pretty much any time.

I am thinking of posts every 8', steel to the top plates. Have a shop fab them up and go from there.

Others have mentioned codes and structure. I'll be having a Naval architect look at it, and codes on houseboats are funny things...sometimes they need to meet Coast Guard, sometimes residential...and all houseboats aren't houseboats. Some are floating houses, some are house barges, some are floating house vessels, some are live-aboards, and they each mean something different.

Thanks for all the replies!

[Sans Absol]

Re: Deck over flat roof on House Boat: penetrations needed.

Sorry about that: didn't know it would embed my answers in the Qoute from Lavrans.

Still learning. Both here and out there.

[NW Architect]

Re: Deck over flat roof on House Boat: penetrations needed.

HIGHLY UNLIKELY that the roof structure on a houseboat can take the live load of an assembly of partiers. I would guess a complete new roof structure, which means a new support structure, which probably means steel tubes inboard of existing perimeter walls below (or within the walls with lots of electrical rework).

When thinking all that through, continue the framing up to be the supports for the railing. Use a round pipe section, then the penetration through the roofing will be easy to flash

[Sans Absol]

Re: Deck over flat roof on House Boat: penetrations needed.

Thanks for your help. I've decided to bring out the architect before I do anything else. I tend to get ahead of myself, and need to gauge whether this is in my comfort zone or just outside of it...not a mile and a half from it!

If we were to consider putting in these steel support tubes, it seems they would need to reach all the way down to the hull/foundation, correct? That would be very in depth...as you mentioned.

Also, the roofer states (and I think he's correct) that the best way to go is to pull of the entire roof deck, re-deck it and go from there. That would open up some opportunities for me, but I think they are wanting "the simple deck that other people have" and I hear "the unsafe and incorrect deck that other people have".

I may need to gingerly walk away from this one.

[Dick Hackbarth]

Re: Deck over flat roof on House Boat: penetrations needed.

I didn’t mean to suggest you shouldn’t do this deck or that it couldn’t be done. But, I do doubt that it can be done with a few pieces of 16" long pipe column supporting a couple of beams and sitting on top of an existing double 2x4 top plate. You should go into this with your eyes wide open, and the help you need is more likely engineering help rather than the help of an architect. You do have to get a whole new set of gravity and lateral loads down to the ship’s hull in a sound manor. And, you should be using wind loads that are appropriate for your coastal area. These new loads are considerably above the water line, so again I ask about ship stability. Then use good sound deck design with due regard for the kinds of vertical and lateral loads a bunch of drunken sailors can induce on a deck, which likely has little lateral support other than what you should be adding. It may be that you can take advantage of the existing house structure to carry some of the new loads, but someone with the right knowledge and experience should help you determine that. Regarding the new roof system, it should have a long life because it is not going to be easy to maintain under the new deck. An entirely new roof structure, on the existing walls, may include the roofing system with some sort of a removable walking surface and handrail system, all in one.

[RocketScott]

Re: Deck over flat roof on House Boat: penetrations needed.

If the roofing needs to be replaced have you (or the architect) looked into putting a walkable membrane down as the decking/roofing surface? You may just be able to remove the old roofing/sheeting, beef up the roof joists and put a pitch on them, resheet, and get a vinyl guy to put down the membrane. Just a thought. It's hard to tell because as was said before there is a broad definition of "house boat" in Seattle.