Replies

1. 
   zendo | Dec 31, 2004 06:40pm | #1

   Always cut the shingles back, a lot of bad accidents involving improper deck attachment.  People are getting killed and seriously injured because of tricks, and underbuilding.  Lag bolts, pressure treat, proper flashing, proper size hangers... the engineering is there for a reason.  Safety is worth the expense... its a lot cheaper than court, lawsuits, and fatal accidents.

    

    

1. 
   Scooter1 | Dec 31, 2004 08:50pm | #2

   The detail for attaching decks has been beat to death over the past few years because of deck failures. Think FHB and JLC have at least two articles showing that detail, in detail.Cutback the shingles, use lag screws and lag bolts with washers to connect the rim joist to the structure. Flashing is tricky, and yes there is a spacer technique which allows moisture to flow between the two rim joists, or another method that installs counterflashing above the deck rim joist to protect that connection. I use the latter method.Of equal importance is the simpson ties used for the deck joists and they must be full size, e.g., don't use a 2x4 tie for for a 2x6 joist. That was the cause of the latest Michigan deck failure.Good Luck and do some reading before starting this project.Regards,
   Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934

2. 
   Piffin | Dec 31, 2004 09:58pm | #3

   I replaced a deck and repaired the rotted joists and band on a house built in the seventies with deck attached over shingle siding that way.
   My assessment is that after time, the load bearing more heavily on the lower portion of the PVC made it cut in there and ope3n at the top. Rain got in at top of PVC washer and could not run out due to pressure seal there. So it then followed the lags into the framing of the structure. The cedar shingles were still in decent shape, but the framing behind was turned to mush - black icky nasty mush.

    

    

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3. 
   davidmeiland | Dec 31, 2004 10:14pm | #4

   Adding a deck to an already-sided wall is a major undertaking. You need to strip back the siding/shingles to expose the building paper up to and above the level of the deck ledger you want to attach. Install the ledger over the building paper using machine bolts and either wood or metal spacers behind the ledger to keep it about 1/4" off the wall. Install a metal z-bar flashing over the ledger and under the building paper above. Install the decking, and then re-side the wall down to a level about 3/4" above the decking.

   If any of the building paper is at all compromised during the work, you need to replace it. If you're doing a really nice job there are some good places to use bituthene or IWS in addition to building paper.

   As you can imagine it's a helluva lot easier to do the work while the house is being built rather than as an after-thought. Interrupting a drainage plane and then restoring it is tricky at best, sometimes nearly impossible. Depending on the circumstances it can be easier just to make the deck freestanding rather than using a ledger.

4. 
   DanH | Dec 31, 2004 10:55pm | #5

   Either cut back to the sheathing and lag in a ledger board properly (with proper flashing) or build the deck self-supporting and have it stand off an inch or two from the siding, so it doesn't promote rot.

5. 
   MojoMan | Dec 31, 2004 11:27pm | #6

   The above advice is all good and sensible. The suggestion to build your deck free-standing without attaching to the house is particularly good if digging and concrete work is easy for you.

   I'll risk the wrath of my fellows here. If the shingles are in very good shape, I think the spacer idea is OK. I'd use pressure treated (or Trex) spacers rather than the PVC pipe. Place one spacer block (approx. 5/4 x 3 x 12")  every 16"-24" (depending on deck size, etc.) behind your ledger. Don't bridge across shingle butts with the spacers. You want a nice flat, solid bearing surface. Use heavy galvanized 1/2" lags into the sill or bolts through the rim joist. Pre-drill through the ledger, spacer, shingles and sheathing. If you want to be extra careful, put ice and water barrier behind the blocks, taper them to compensate for the angle of the shingles, and angle the top of the blocks to shed water faster. Caulk the top of the blocks.

   The important thing is to make sure water won't get trapped between the ledger and the siding.

   Al Mollitor, Sharon MA 

1. 
   davidmeiland | Dec 31, 2004 11:34pm | #7

   When I attached the ledger to my house I ripped cedar strips 1/4" x 1-1/2" x 7" long and installed them vertically on the back of the ledger at 16" OC. I then drilled the machine bolt holes thru those spacers and bolted the ledger on. I think that takes care of about 50% of the possible rot problem. The other 50% comes from lack of correct flashing on top of the ledger. Do both and you're 100%. BUT... suppose you have a client who parks a huge number of planter barrels on the deck against the house and then soaks them with the hose every day... then all bets are off and you absolutely need the flashing.

   Edit to emphasize that machine bolts are what you want, not lags. 90% of the time you're going into 2x rim joist or blocking. If you somehow have the luxury of lagging into a 4x, then OK. Here the BI pokes his head under the house and wants to see the nuts and washers on the bolts... no lags.

   Edited 12/31/2004 3:36 pm ET by davidmeiland

1. 
   Piffin | Jan 01, 2005 12:01am | #8

   On that one I repairedd, if they had used bolts and caulked around the sleeve, it may have done OK. but that only if they had also used the fact that lags can be re-tightened over time.Same with mongo's suggestion of PY blocks to bolt thru. I would have no problem wiht that approach on solid siding if the blocks were tapered to fit soundly to siding, god caulk or PL Premium were placed between, and bolts were kept accessable so they could be tightened over time. 

    

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