I have a large deck, not sure the measurements but maybe about 12 x 30. We got a buttload of wet snow in December before the ground was fully frozen, and thanks to physical problems I never shoveled it off like I usually do. Then recently we got a few hours of steady rain then freezing temps, so the snow is like mounds of ice now. Looking out the window the other day I noticed the railing was arched upward, but I just thought it was warping. But when I went out there I was surprised to see that part (and only part) of the deck had sunk 4 to 5 inches where it butts against the house.

I am feeling better so I removed some of the icy snow and started to jack the ledger board up about an inch when It dawned on me that I don't really know what happened. I'm not sure if posts and footing sank in unfrozen ground (in which case it would be dumb and damaging to keep jacking), or if the deck just broke free from the house, or both, or something else. But I decided I should stop trying to lift it and just keep it supported until the ground thaws, which could be a couple more months.

Other suggestions?

 

Can't really give you advice sight unseen. You can see it, we cant.

 

A deck constructed correctly should be able to hold a lot of weight, if something has "sagged" you really need to look closely at that thing to understand what is going on before someone gets hurt!

 

You've got serious structural problems. The deck should easily support a snow load.

 

You've got serious structural problems. The deck should easily support a snow load.

My reading says anything above 3 to 3.5 feet can cause problems. We got 37 inches of heavy, wet snow in less than 2 days December, not to mention the snow that came after and the steady rain that saturated all of it and then froze last week.

 

Can you confirm the footers for the support posts are correctly spaced and go down to below the frost line?

 

It looks like the ledger is/was just screwed in with no bolts, at least in the part I can see -its multilevel and I can only see under the raised portion easily. Deck is also 25 years old. Will try to get some pictures but due to snow and my unwillingness to craw very far under it at this time they won't show a whole lot.

I can't confirm anything about the footers. The deck was newish when I bought the place but the ground is snow covered, frozen solid and will be for some time yet...

 

After looking things over as well as I can, I see no reason to think the footers have budged. I could be wrong, but it seems they held tight leaving the attachment to the house the weak link. You can see some of the broken off screws near the shovel. I supported it on both side of that corner for now, not much I can do if I'm not 100% sure jacking it up further at this time is a good idea or a bad idea.

Hopefully the images are self-explanatory. the black paint shows where it sank. The first two pics are the above and below deck view from almost the same angle of the corner. I'm hoping there are bolts somewhere (maybe just not on the elevated portion's ledger?) but I don't see any at the corner and I'm not inclined to crawl the whole length of the longer, floor-level portion right now. if ever. It has sunk a lot less than the higher level, and the sinkage gradually decreases to nothing as you move to the right away from the corner.

 

Yep pretty shoddy construction. Screws should never have been used to fasten the ledger. Jack the ledger up and bolt it if you have access to the interior, lag it to the rim joist if you don't. See the DCA6 Prescriptive Deck Guide for details on ledger attachment. 1/2" bolts or lags... 2" from top, 2" from bottom, typically in an alternating pattern.

Hard to tell from the photos but also looks like no ledger flashing and it was put right on top of the siding. Double no-no.

 

crappy install on ledger. jack up ledger and surrounding area to a level position. and temp brace it. install lag bolts with a washer through ledger and in to rim joist of house. use 1/2 inch galvinized 6 or 7inch lags. and for sane of mind you could get some treated 4x4, 4v4 concrete post blocks ( they just sit on ground) some HD lag screws, treated 2X8 and instal a few 4X4's down the line to side of joists sitting in concrete blocks, then run 2X8 under joists and along 4X4 posts lag screwing to 4X4 post. extra beam never hurts and think it would take a lot odf stress off ledger. some prefer not to connect to the house and just install a beam close to house. if it is concrete you have to go into just use the lag concrete ones.

 

Yep pretty shoddy construction.

Well it survived more than 25 years of Minnesota winters so it did OK for shoddy contruction

Screws should never have been used to fasten the ledger. Jack the ledger up and bolt it if you have access to the interior, lag it to the rim joist if you don't.

I just had the entire crawlspace sealed and insulated 4 months ago, so without tearing all that apart I no longer have access to the interior. of the rim joist. Lags it is then.

See the DCA6 Prescriptive Deck Guide for details on ledger attachment. 1/2" bolts or lags... 2" from top, 2" from bottom, typically in an alternating pattern.

That I can do...if I can get under there.

Hard to tell from the photos but also looks like no ledger flashing and it was put right on top of the siding. Double no-no.

I believe that is correct. Its definitely over the siding, and so it must remain...

 

crappy install on ledger. jack up ledger and surrounding area to a level position. and temp brace it. install lag bolts with a washer through ledger and in to rim joist of house. use 1/2 inch galvinized 6 or 7inch lags.

I followed you this far, but the rest was not clear

 

Jack up the deck to be in the proper position. Then drill through the ledger and through the house's sheeting and rim joist. Then through bolt with 1/2" hot dip galvanized bolts. For the latest decks I've done the pairs of bolts could be no more than 24" apart.

 

OK, snow is finally melting. I have the deck jacked up to where it should be again. I threw in a temporary support and will make one or two more before I get too far under it it.

I will get a couple dozen 6 or 7" lag screws and washers. I'll maybe/probably need to buy a drill bit that large/long, and I'm not sure my old cordless drill is up to the drilling job or not but I can try on and see.

Since I'm not entirely sure what all I am drilling through, do I need a special bit? Is it safe to assume that since most of the deck is at floor level, that I will be screwing the ledger into the floor joist or do I need to verify that somehow? I really don't want to cut up the brand new crawlspace insulation.

 

Before going and buying lag bolts you first need to open up that part of the house, usually from the crawlspace, to see what you will be attaching to. Yes, you will need to take down the encapsulation. Depending on your home's construction you might have to add blocking between joists to provide enough material to lag bolt into. But, once you have the inside open using through bolts & nuts is a more sound method than lag bolts.

Do not just go buy long lag bolts. You do not want bolts that are too long and pass through what your attaching to. They need to be the correct length.

 

Very unlikely that I will "take down" the encapsulating that took several guys weeks to prepare and install only 6 months ago. At most I might cut a peek hole. if that isn't sufficient to determine what I'm dealing with I'll have to settle for something else, like above grade supports.

 

Here's what I found. They hadn't finished sealing the foundation but they have sealed the joist spaces. So you can't see the exterior floor joist.

First a view from the outside.



The left corner of the foundation is the nexus of the problem, where I have it jacked up. The raised portion of the deck is to the left of that, but you can't see it. There is romex that comes out just left of the vent and goes to the septic. You can see that the ledger mounts one level above the vent.


View of that vent from the inside. Romex heading out to the right of vent. Just above vent is where the deck ledger mounts, but this is hidden by planks of foam board. I see no reason to think anything is really hidden though. Behind that plank is the perimeter joist, or whatever that one is called.



This just shows what has been done all along that side, although this is a different side of the house. All of the joist spaces are blocked in so you can't see anything. Its even worse on the problem side because you have the first inboard joist also blocking view of the foam planks behind it. Cutting a hole wouldn't show me anything much, I'd have to tear it all out and there is no way I'm taking all of that out just to see that there's nothing behind it except floor joist. I searched all along the problem wall and saw no Romex or pipes or anything anywhere else except that one spot, and there may be a heat duct that I might need to avoid.

Do you agree that it should be pretty safe to lag it now?

 

"Do you agree that it should be pretty safe to lag it now?"
No, because you don't know what you are bolting into. Some rims are only 1/2" OSB, others are a single 2"x board while my inspectors don't allow lag bolting into anything less than two layers of 2"x lumber. So, if your house has a single rim you'd have to add blocking on the inside to provide enough "meat" for the lag's to bite into. Then, the tapered end of the lag must be completely exposed on the interior so the inspector can verify that you used long enough lags.

 

Get under the deck and pull the fiberglass out from around the Romex and see if you can tell what's above your bottom plate and what's behind your sheathing.

 

I think I found my answer, or at least good clues. I am 99% sure it is a single 2" board perimeter joist. I looked at an easily accessible vent and there is only a 2x6 sill plate above it. There is 2" foam plank on top of the sill plate, against that presumed 2" perimeter board (I highly doubt it is OSB, which was around only 8 years when this was built). But there's still 2" of space on top of that sill plate, so there is most likely NOT a 2nd 2" perimeter board. I might be able to find a more definitive answer if I take out the access door. It is framed but I might be able to see something, or at worst I can find out when the weatherization crew comes back to finish planking off that corner where the deck is. It wouldn't be that hard for them to pull off one piece of foam, but I'd rather not wait for them if I don't have to though because they may not come until fall

That fiberglass by the Romex is just blocking the vent and probably hiding the footer. That's exactly what I just described in the above paragraph, only I looked in a different vent that's easy to get to. That other one is a 50 foot belly crawl but I expect it will look the same

 

I have now determined with 100% certainty that there is only a single 2-by that forms the perimeter joist. I am confident that I have mapped and can easily avoid any obstructions like wiring or heating without tearing out the foam planks. I will not be adding an additional layer of 2-by. This will never be inspected and there are no permit or inspection requirements for reattaching a partially detached deck. So I have a single 2 by ledger and a single 2 by to attach it too

So what is the best way to do that, since it seems screws are not up to the job? Would using short, 2.5 or 3" lag bolts not be a heck of a lot better than what I had, seeing as it took the heaviest snowfall on record (12 feet) to cause the problem?

The very short section that is above joist level will have to settle for screws again. But that part only went along for the ride, I'm sure its the much longer section at floor joist level that didn't hold up because it had much more snow on it.

 

Use an alternating pattern of 1/2" x 4" lag bolts (with washers), assuming you have 1/2" or 3/4" of sheathing covering the rim joist. See DCA 6 figures 14 and 19.

This assumes your ledger conforms to the one shown in figure 14.

 

just need to add that the rim joist is solid lumber, not osb or anything weird

 

New (and hopefully final) discovery: There is indeed some sort of fiberboard underneath the siding. Since the deck is attached over the siding, which is 3/8" thick and the fiberboard appears to be about 5/8, so maybe for good measure I should add about 1 or 1 1/8" to those lag screws?

The other thing I'm noticing is that at the corner where it sank the most, the ledger has pulled back from the house about a finger's thickness (maybe 5/8"?). 5 feet inward its about half that and that gap diminishes to nothing in another 5 feet. But I wonder how this should affect my repair. At the very least I think I should work from where there is no gap toward the gap end, in hopes that it gradually cinches tight. But I'm not sure if that will do it. Seems smarter to make sure its snug before lagging it. Not sure how I can apply a horizontal force on it other than nudgng it with my truck bumper. And that sounds like it could turn into a hold my beer moment...

 

You might want to use 1/2" x 4 1/2". Drill 3/8" pilot holes and take note of how deep the bit is when you feel it pass through the rim.

The drawing together is just another reason why bolts are preferable.

 

Thanks, I'll drill a test hole before buying anything. I'll also experiment with ideas to push things together. My truck idea led me to a better idea, which is using the truck as an anchor for using a bottle jack at 90 degrees and some blocks for a horizontal force. I think that should do the trick and do it safely.

 

My drill broke through after 4" and before 4.25 inches. This was on part that was pretty snug against the house still. Should I go a little longer or is 4.5" still good?

 

If you're going to jack against something to tighten the gap behind the ledger then 4.5 is good. Otherwise use 5".

 

New problem. I hadn't noticed that one of the 2x8 deck joists is severely cracked, about 2.5 feet long. Its the one that come right off that corner where the deck dropped the most. It isn't cracked all the way through either dimension. Should I just lag bolt one sister board or put one on each side? The longest sister board I can use is about 6 feet. The crack is about 28 inches long and fortunately its pretty close to smack dab in the center of that 6 foot space I have to work in.

 

I got a bunch of lag screws and washers for reattaching the deck, a bunch of 1/2 by 4.5 inch for most of it where it didn't sink and some 5 inch for where the sinking and separation occurred.

I can't find any legible markings on the deck ledger, and I surely don't know what the rim joist species is. Should I assume the ledger is a Type II and go with 15/16 pilot holes and 1/2 for the unthreaded shaft? Google is suggesting that most deck frames are now southern yellow pine and Doug fir which are Type II, although this is 25 years old

see table at bottom

 

You do not drill a 15/16 pilot hole for any part of a 1/2" lag. I'd suggest 5/16 for the threaded portion.

 

Hahaha, sorry for that typo I meant 15/64 obviously, but I really meant to type 5/16 as that table I linked suggests for 1/2" screws in Type II wood. 15/64 is for Type III wood

I just am not 100% sure I have Type II wood, but it seems like the safest guess

 

Yep, most treated wood in these parts is southern yellow pine and it's pretty soft.

 

Its hard for a pine though, lumping it with Doug Fir