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  1. #1
    Join Date
    Apr 2010
    Location
    Reisterstown, MD
    Posts
    29

    Question 'Ceiling' under deck

    Tomorrows inspection has an elaborate composite deck with a first floor walkout underneath.
    Listing pictures show what appears to be a conventional tongue and groove ceiling under the deck.

    Thinking about this brought this question to mind; how are the deck joists provided proper drainage and drying?

    Anyone whose seen this before, some pointers are needed.1338457_15.jpg

    Inspection Referral
    Bob Kenney
    www.IndependentHomeInspectionMD.com
    Call or TEXT : 410-504-3751 rkenney74@comcast.net

  2. #2
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: 'Ceiling' under deck

    Bob, I have seen it a few times. I had one this Spring that was a train wreck. The key is that the joist should not be getting wet. When they build the deck they basically are making a shower pan on top of the joist without a center drain. The deck should have I believe a 1/8" fall per foot towards the outside edge and must be flashed at the house wall side and have a drop edge flashing on all outside edges. The railings are another trouble spot. Flashing is a huge detail at the railing post. The deck boards (Trex or whatever) on the decks I have sene are pretty much a floating system so that screws do not penetrate the waterproof membrane.

    The very first thing I look for are stains on the ceiling or underside of the deck. If you find water stains you have a leaker and I would say most will leak at some time....

    Hope this helps..

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  3. #3
    Join Date
    Feb 2008
    Location
    New York
    Posts
    869

    Default Re: 'Ceiling' under deck

    I also find these finished bottom decks to be a common problem and Scott pretty much summed it up with the shower pan explanation, but would like to add to his list.

    It's hard to tell in the picture, but what is protecting the bottoms of those columns from water absorption/damage?

    I can't see the top of the deck, is water flow promoted or impaired?

    Whenever I have this "closed box" condition (my knees jerk ), I like generously adding eave vents to the bottom to promote ventilation. I usually spec the small round ones that can be installed quickly with a hole saw. If the ceiling material is typical vinyl like used for eaves, I would install some vented ones. I like to vent far and close to the house.

    When building the floating deck, I recommend doing it in sections that are not too large so they can be removed (reasonably easily) for maintenance. Make sure there are no nail/screw heads sticking out or sharp edges where the deck meets the roof (also make sure the carpenter did not leave any stray nails/screws or debris on the deck and is not walking on any while working.)

    I've seen some with cushions or flat plates below at support points. The floating deck panels should be configured (at the bottom) so they promote drainage and allow the water to flow easily.

    If needed, some type of drainage has to be provided so any water can drain away easier than not.

    Last edited by Steven Turetsky; 10-14-2014 at 08:00 AM.
    Steven Turetsky, UID #16000002314
    homeinspectionsnewyork.com
    eifsinspectionsnewyork.com

  4. #4
    Join Date
    Apr 2010
    Location
    Reisterstown, MD
    Posts
    29

    Default Re: 'Ceiling' under deck

    Thanks for the quick replies. Had I paid more attention to the latest issue (Nov.) of Fine Homebuilding I would have seen their article on rooftop decks which essentialy are the same thing (dry underneath).

    Professional Deck Builder (July/August 2014) also has an article on rooftop decks.

    As pointed out flashing is important. The recommendation made in the article was for a 1/4" per foot slope and a 1 1/2" drop between the deck and adjacent interior floors.

    Again thanks for the replies and I'll try to post some pictures as followup after the inspection.

    Bob Kenney
    www.IndependentHomeInspectionMD.com
    Call or TEXT : 410-504-3751 rkenney74@comcast.net

  5. #5
    Join Date
    Apr 2008
    Location
    Massachusetts
    Posts
    191

    Default Re: 'Ceiling' under deck

    My guess is that it's a proprietary system. There are several on the market. Just Google "under deck drainage systems". Dekdrain.com, underdeckoasis.com, and dryjoistez.com are a few


  6. #6
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: 'Ceiling' under deck

    The other way to look at that photo is that you have a covered porch ... with a deck above the roofing - not hard to do and I've seen it done on many buildings.

    Granted, whether that is a roof with a deck above it or whether it is a deck with a pan underneath, eventually the waterproofing (roof for the porch below) will need to be replaced - so design and construct the deck with removal in mind, that will make the work a lot easier and cause far less damage to surrounding areas.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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