Rot under deck / in basement

On one of my basement walls the plywood is rotted. The water is coming from the deck but I don't actually know where or why. I'm going to start pulling boards off and checking it out tomorrow. I have some pictures posted. My guess is something was built incorrectly with the deck.

I'm hoping someone will say "Well I can tell just by looking..." haha.

 

It's not a problem with the deck unless the ledger board is collecting water. The problem has to do with the foundation or the way the water flows off of the deck. How are the gutters & downspouts?

 

I kind of doubt the problem is the deck. But you could pop off some of that 1x6 and see if there is any flashing where the ledger meets the house. I can't tell if there is z-flashing on top of all the 1x6 trim or not. But there should be.

If there has never been any drywall over that insulation, the sheathing behind the insulation probably has had tons of frost on it all winter long, and this is probably the real reason why the sheathing is wet and rotten. Moisture from the house (comparatively warmer and more humid than the air outside) can get past the kraft facing and freezes on the cold sheathing (which is basically the same temperature as it is outside) which acts like a giant dehumidifier... except the moisture keeps building up behind the insulation like a freezer that's never defrosted- it finally melts when it gets warm enough, but can't properly dry out with the kraft facing over it. Does this sound familiar?

One addition: Your ledger boards should be bolted or lagged to the house, not just nailed.

 

Xsleeper, should it look like the picture I attached?

You can see under the deck that there is flashing under the ledger board going over the siding, but that wall leaks as much as the others. Based on what you're saying, water must be collecting and dripping down behind the ledger.

I doubt it is the condensation issue you were talking about because when it rains, you can see water dripping in. Especially in that section in the pictures where you can see the Tyvek thru the wall.

 

Yes. I'm guessing the ledger flashing was omitted and maybe the 1x6 and z-flashing was an attempt to flash it. Removing the 1x6 to investigate would be high on the list of places to start. Maybe taking off the one under the exterior outlet first would be a good idea.

 

Everything behind the ledgers was rotted. The plywood, the headers, the top plates, the studs. Spent the whole weekend rebuilding everything. There was no flashing over the ledgers, so for the past 30 years water was getting in behind them and rotting the wood away. I replaced the rotted plywood with new stuff that I painted, and put some of the ice & water shield rubber membrane on the wall. I'll put flashing on the ledgers and I should be good to go.

 

Holy cow.

I think you can be glad you found/fixed it before it was too late! What the heck was holding up the house on that corner? It's amazing nothing caved in the way it looks. You need a pat on the back, and maybe a tranquilizer.

As a reminder, be sure you don't use aluminum flashing on any PT wood, and all the fasteners you use in the PT wood need to be ACQ approved.

 

What happens with aluminum flashing on PT? What kind should I use?

I just read about the ACQ lumber, had no idea about this. I used some Grip-Rite Primeguard screws to for all the new stuff. Maybe I should go over it with some stainless. I want to find some with phillips-head, I hate the square-head and Torx stuff. Thanks for this info.

 

The copper in the ACQ will eat the aluminum. Galvanized flashing is fine, and even then I am cautious and I like to put a strip of tar paper or housewrap between the two just so they don't touch. I figure it's got to extend the life of the metal.

Don't like torx???

 

Here's what happens to aluminum when exposed to PT. IMO, torx T25 is the only way to go. Have you had problems with them?

 

Haha they always seem to round out much easier than a phillips.

What's a good "wood filler" product, if such a thing exists? I have some small spots to fill after I chiseled away the rotted plywood. I just want to fill in the gaps before I put new tyvek and cedar on.

 

If they round out, its probably because you are using a T20 bit in a T25 screw. Torx are the only way to go. Filling in your sheathing is probably a waste of time. But you could smear on some Bondo if you just don't want the next layer to dip in when nailed or something. You could also just shim it... doesn't have to be pretty, it's getting covered back up.

 

Definitely not using the wrong size... but my Torx experience is solely with cars, not decks. I just like the idea of screws rather than nails for the possibility of removal.

 

A few more pics... You think the ledger board I pulled off is still good? I had to chisel in a little bit to get the nails out.

 

What size flashing should I get? How much is needed above the ledger (behind the 1x6 trim). I was thinking 10" should be good, 5" above and wrap the wrest over the ledger board.

Just saw that they make preformed deck ledger flashing, I think I'll go that route.

 

Some more pics... I used some 1.25" screws in the joist hangers, hope that's good enough. I didn't think they had to go all the way into the header / top plates. Or am I wrong?

The preformed flashing fit in quite nice.

 

You need to remove the screws and install galvanized joist hanger nails. Screws are not approved for installing joist hangers and do not have the shear strength that nails do. I think the diagonal nailing holes require 8D nails (Hot dipped galvanized of course) It says what you need on the side of the hanger, I just can't read it in your picture.

 

I have a box of 8d galv. Thanks for the info.

 

The fasteners in the flange of the hanger should be 10d hanger nails or #10 Simpson hanger screws (the only approved type of screw) and the ones that are angled should be 16d galvanized nails.

 

16d on the angles? Why is that? It seems like those are doing the least amount of work.

 

Why? Because those are the nails specified for a hanger of that type! The holes at an angle require 16d nails because the joist must actually be toenailed into the ledger... not simply attached to the hanger. All joist hangers are engineered to meet weight loads and lateral forces (pull out) so you have to use the nails specified. Doing it right the first time is a lot better than having an inspector come along and tell you you have to pull them out and do it over again.

If you look at a Simpson catalog online, it would tell you all this information, and you could look it up for yourself.. There is a chart in front that also shows all the nails. I have one in front of me. The 10D common nail they show is almost exactly the same size as the 16d sinker that they show. In their chart, 10d common is specified but the notes in front indicate that you can substitute 16d sinkers. 16d galvanized are usually more commonly used.

 

Oh ok, I see the chart now... a good piece of info. My paranoia of thinking about taking this apart in the future if I had to was why I did the screws. I see they say you can use their brand of structural screw.

Tx for the info.

 

During this next round of work this past weekend, I noticed that one of the other ledgers (on another wall, no joists attached, not sure if the correct name for it is 'ledger'), there was only 2 nails in it, one on each end. While I was pulling deck boards up the ledger started coming off the wall... infuriating... ****ing hacks.

Anyways... I want to use the Simpson structural screws for my hangers, but there's 4 kinds: #9 x 1.5 & 2.5, and #10 x 1.5 & 2.5. The catalog doesn't seem to specify which, other than the fact that #9 replaces 10d and #10 replaces 16d. I'm assuming since the LUS28Z hanger says (actually LUS28Z is not listed, but it matches the dimensions of the LUS28) 10d, I should go with the #9 x 2.5?

 

Their chart shows to use the #9 x 2.5

Strong-Drive® SD Structural-Connector Screw

 

What is the appropriate size screw for 5/4 PT decking?

What about 1x PVC trim? I got 2.25" stainless.

 

See on the exterior corner how the vertical trim doesn't go all the way to the deck? When I redo this I wanted to make the vertical piece go all the way to the deck, or would this look stupid?

I also wanted to put the 1x6 on the side toward the camera, and the 1x5 on the other side so you don't see the seam all the way up.

 

IMO it would be better for the vertical trim to end at the deck that way water can't get trapped between it and the bottom board. Is there flashing over the bottom board?

 

Yes there was. It's very hard to see it in the picture.

 

Vertical boards should almost always run top to bottom. The z-flashing will butt into it. with an upturned flap, with sealant under that side.

 

What is the reason for that? Do you need sealant between the end of the horizontal piece and the side of the vertical piece?

 

Yes, the more you can do to prevent moisture from getting under the wood or paint - the longer both will last.

 

In my case, both will last forever cause I'm using PVC... but I'm assuming it's to protect the stuff underneath as well.

 

Ya, hidden rot can be even worse ..... but then you already know all about that

 

Ha...... good one.


Haha.

 

I figured you guys might be able to shed some accurate insight on this... what do you think a deck builder would have charged me to do this job?

I'll post more pics later but I also had to rip up a bunch more deck boards up to install flashing against another wall. Fortunately there was no rot cause that part of the deck is a couple feet under and overhang.

 

Couple questions...

Do I need flashing under the bottom of the ledger and over the siding?


Also, what's the best way to join these two joists? Put a sister board with carriage bolts on them?

 

I think flashing under a ledger won't do much good, unless you are anxious for the ledger to rot out and require replacement. Trapping water is never preferable to letting it freely drain and evaporate. A sistered, full-depth 2x should work well to splice the two members together. I'd use galvanized machine bolts with flat washers under both heads and nuts myself. Once you apply too much torque on carriage bolt nuts, the bolts have a tendency to spin and be free-wheeling. Once that happens, your tight splice connection is anything but tight.

Also, to develop the full strength of a joist hanger, you should install nails in all of the fastener holes, not skipping some as shown in the pix. Also, I always drive home all of the prong tabs before inserting fasteners, which you obviously haven't done. They were put there for a reason, so why not use them?

 

Thanks. I think I need to bend up the flashing, and add a bit more, to make it go over the ledger and the sister board, so water doesn't get in between the two. I'll use the hex bolts on the joist, and lag screws into the ledger. What did you mean by "full-depth 2x"? How long should the sister board be?

I actually only have one hanger that is missing 2 screws, the rest of them have all 10. They'll be in soon.

 

I meant sistering with a 2x the same size as the members being spliced--if they are 2 x 6s, then you sister them with a 2 x 6. The length of the splice member depends on the function of the members being spliced. Judging from the photo, not much load is presently being carried across the connection, since it's presently an open butt joint. A 3' splice should work, although longer is better if loading is heavier than what appears to be the case. Don't forget to (slightly) counter-bore the splice board where it straddles the existing lag bolt head(s)--you want the sistered member to be drawn up tight to the members being joined.