Expert: Dan Griffin - 7/15/2010

Question
QUESTION: Hi Dan:
Thank you (in advance) for your advice. I read the article that was posted in 2008 regarding attachment of ledger board to EIFS siding for a patio cover. Since my siding has 1" or so foam board under the
cementitious coating, how does the ledger board actually attach to the studs? Does the ledger have to be actually be in contact with the studs themselves? I was reading a section in one of those Ortho do it yourself books and there wasn't much info. It did say that the siding had to be cut out so that the ledger is attached to studs directly. Will the ledger be stable if I attach it directly over the EIFS siding(i.e. leave the foam board in place)(with fender washers of course). I am concerned about the foam board under the exterior coating. Will it compress over time if the foam board is "sandwiched" between the ledger board and the studs? Will this cause an issue over time?
I have a southwesten style flat roof home built in 2005 so the exterior walls have parapets (no eves to protect the attachment point to the house from rain, etc.)How does one get the Z flashing
tucked under the foam/EIFS siding?

ANSWER: Carol, ledger board attachment for decks is a major concern.  There have been some serious deck failures and the potential for water problems is great.

One alternative is to not attach the deck to the house.  Build the deck as in independent free standing structure with sufficient knee bracing, etc to deal with movement.  This may sound like a big deal, but really isn't much more material or work.  It would still seem prudent to fasten a few times to the rim joist, but you are no longer depending on the ledger bolts to function in shear.  One good thing is that if it not structurally tied to the house, the footings do NOT have to go to frost depth.

I would not remove the EIFS, though that can be a legitimate approach.  The flashing work becomes a big deal and will require working with an EIFS specialist.  There probably will be a rim joist carrying the second floor joists, but you do need to verify.  It would be best if you can fasten the deck to that rim, , but you may have to reinforce its attachment as you will be pulling and pushing on it in a direction it was not designed to resist.  The very best would be to expose the rim joist on the inside to allow inspection, bolting, and reinforcing.  The rim joist may require additional attachment to the joists as it was not intended to function in this new roll.  The fasteners should not run down the center of the new ledger band.  They should stagger high-low to avoid creating a fracture plane down the center of the ledger.
 
Drill through the EIFS to install pieces of pipe slightly longer than the EIFS thickness so that when the ledger is bolted up it will actually be slightly off the surface of the EIFS, yet bolted tight.  I would certainly have heavy washers wherever pipe, bolts, etc touch wood.  Be aware that ACQ traeated lumbver eats steel, this will require stainless steel.   The steel sleeves can be caulked when installed with a good polyurethane caulk like NP1 so that water cannot penetrate the EIFS.  This can also be done by cutting out small sections of EIFS to install wood blocking from the rim to the ledger and caulk the blocking.  I prefer using the galvanized pipe method as the penetrations are smaller and easier to caulk, and less prone to rotting out.  Make sure there is a slight air gap between the EIFS and the back of the ledger to allow it to dry out after rain, etc.

Your local inspector may have other criteria.  I suspect that this project will require a building permit.  I also suspect that the permit will require an engineering stamp as to lumber type, bearing capacity, fastening details, handrail attachment, stairs for exit, etc.  

Either of these methods should not require flashing, just let the water to go through.  If you are creating a water tight deck, the issues change.  I would still do the flashing with a surface flash with a kick out to allow caulk.  There is one illustrated in Figure 6 at this site:
http://books.google.com/books?id=pJBEMB6kSKUC&pg=PA197&lpg=PA197&dq=flashing+%2B

---------- FOLLOW-UP ----------

QUESTION: Hi Dan: I am not building a deck attached to house but rather a patio cover only. The floor of this patio is cement slab. I want to know the above info in relation to building a patio "cover"(roof) only. No deck.
Thank you so much for your help.

ANSWER: Carol, the answer stays exactly the same as far as attaching the ledger.

The very best way to do this project requires cutting the wall open, attaching and flashing, and repair.  If you decide to go this route, here is an excellent illustration of Z bar flashing:
http://www.roofkey.com/roof-to-wall-intersections.html  
This will require cutting out and removing a section of EIFS to get to the house wrap and sheathing.  When the flash work has been done, you will need to repair the EIFS.

I think I would head a bit of a different direction and not penetrate the EIFS for the flashing.
Attach the ledger with the pipe sleeves.  The pipe sleeve keep from crushing the foam behind the EIFS and violating the drainage plane that I sure do hope you have under the EIFS.  Frame and deck and install roofing material.  Flash on top of the roofing material with the caulk trough style flashing with a good urethane caulk.  You will need to monitor the situation and if there are any signs of water penetration through the EIFS, you can then cut into the wall and install the counterflash.  I have installed commercial work with this system against rough stone, concrete, and EIFS with success so far.

---------- FOLLOW-UP ----------

QUESTION: Hi again Dan:
Thank you for all your info. What do you mean by "violating the drainage plain"? Also, are there some general rules for how many pipe sleeves per line foot of ledger? Should I stagger them? Will I still have to drill a hole for each pipe sleeve down to the house frame studs? Is a 1" pipe that is 2" long adequate? Thank you.
Sincerely,
Carol Castro

Answer
Carol, there have been many EIFS failures.  EIFS is extremely water proof and moisture that is trapped inside the wall, whether from misplaced vapor barrier, cooking, showering, or infiltrated rain cannot get out and rots the wall studs and plates.  To counteract this problem, most professional EIFS contractors have started installing a drainage plane under the EIFS foam.  Here is an example:
http://www.senergy.basf.com/en/wall_systems/eifs_drainage/Pages/default.aspx
and
http://www.toolbase.org/TechInventory/TechCAD.aspx?ContentDetailID=988

It is always good practice to stagger any fasteners in any type of rim or ledger.  This helps prevent cup warping, takes advantage of the top fibers which are in compression and the bottom fibers that are in tension.  It also helps avoiding cracking the board because all the fasteners are on the same grain line down the middle.  As to how many, it is totally subject to what you are fastening to.  If you are in the studs, at best they will be 16" apart.  If it is a rim joist, you can put them anywhere.  I would think a good fastener every 16 would be fine.

Certainly, you must drill each pipe sleeve.  The object is to get the EIFS out of the way so you can get a structural fasteneer into the wall framing.  The EIFS is stryrofoam, it has little or no strength for either pull out or compressive forces.  It is there as insulation.  I don't know what you have under the EIFS - it might be plywood, Densglass type sheathing, brown drywall, etc  Be generous with type and quantity of caulk as you seal these sleeves.  I DO NOT believe in silicone anything.

1" pipe is what I had in mind.  YOu can buy a piece of galvanized iron pipe.  I have no way of knowing how deep your wall will be.  Let's do some guessing - I suspect the finish coat of EIFS is about an 1/8", the foam is probably 1", the sheathing is probably 1/2".  If all that ends up true, the 2" nipples sound reasonable.