45 degree sway bracing from the 4x4 to the header,(sway braces are usually 4x4 as well),should stop the sway.

Temporary posts either side of the existing 4x4's will allow you to cut out around the base of the posts,dig out and around to form and pour footings, putting in a post base as well.

Sounds right to me. You still might want to run it by the engineer who checked the house plans, if there was one.

I'm still shaking my head over the idea of supporting the deck with 4x4s on patio stones(!) Not too late to switch to 6x6s.

Thank you, both. I'm very grateful for your advice.

worthy, it's not patio stones, it's concrete, but I suppose it's the same problem.

sierraeast, thanks; we'll tell him this is what he has sto do.

DH wants me to ask this also: What is an acceptable amount of rack on a deck of this kind? What is the proper way to measure rack?

Thanks again if you can tell us this.

Susanka

I would not normally come in on top of sierraeast and worthy but your deck construction appears to be inadequate.

My experience is limited but you should immediately address your ledger attachment and support post size with your GC. Ledger attachment with lag bolts (screws) is within IRC code but the spacing appears to be too far apart. Builders I worked with generally placed a lag between each joist space and alternated the lags high-low-high-etc. One builder insisted on using through-bolts whenever practical (for stronger holding strength). Ditto worthy re your support posts. 8 ft is too high for 4x4s -- replace with 6x6s. Bracing per sierraeast works very well but keep in mind it will be visible from your patio below. You might want to consider "letting-in" your cross-bracing along the bottom of your deck for a more finished look (notches are cut out to fit the cross-bracing into the underside of the decking to keep everything flush along the bottom) It's more labor but it will be a big help if you ever decide to install an under-deck water shield to keep the patio dry. Finally, footers for your support posts, poured to the required depth for your climate/area, are essential (a 4" slab doesn't cut it).

I recommend you read the article at the following link for more details: http://www.nadra.org/consumers/deck_inspections.html. This link to Simpson Strong-Ties deck construction provides good diagrams for connections -- http://www.strongtie.com/ftp/fliers/F-DECKCODE07.pdf. You could also ask your local code office for specs or ask to read their code book.

Deck deflection should be the same as your house floor and racking should not be noticeable (I don't know what the acceptable engineering tolerance is). I don't want to alarm you, and some on this forum may think I'm nuts, but I am extra cautious regarding deck construction. My own deck is approx 60x12 and it will see a lot of use. A crowded deck is not the time to wonder if any movement is within safety standards.

Again, many thanks to all three of you and, terry t, for your long and detailed post. I especially like the let-in cross bracing to keep our view intact. We are calling the GC today.

As usual, this forum seems to be filled with folks who are amazingly generous with their help.

Susanka

Your deck should not rack at all if built right. Terry's idea of a "let in" wind brace sounds good, but kinda hard to do with decking all ready in place. You can simply add the brace to the bottom of the joist going from ledger @ house to outside rim joist on a 45 degree angle. A treated 2x4 works good for this. It's better to put the 2x4 on the bottom as opposed to cutting the joist anyway because you weaken the joist if you cut in the wind brace. If you want it flush then use metal wind brace straps, the kind with little holes all ready in them, make an x with as descriped with 2x4 wind brace.

He is right about the amount fasteners on the ledger, add a few more so you have one on each joist & 2 on the ends. I like to use 1/2"x5 1/2" wedge anchors for this.

The 4x4's should be ok, but there is not enough of them. With a 24' long deck & only 3 post that means one on each end & one in the middle. A doubled up 2x8 rim joist cannot span 12' & pass building codes. You will need 3 post between the corners, one every 6'. It's not that the post are undersized, but they are over spanned.

Al @ alscustomdecks

I would not be throwing any "new house move-in" parties anytime soon until that deck is rebuilt.

There are several areas of concern but first was this designed by an architect/engineer or something the builder threw together? What building code is in effect for your area?

The 4" concrete slab is not sufficient to support the deck. Footings should have been poured.

The IRC requires 6X6 posts (unbraced) for any deck over 8'. That is measured from the top of the footing to the bottom of the girder so you might just meet code but I would not have built it that way.

Lateral bracing is required by the IRC for decks more than 4' high. It does not sound as if the GC did this & that could certainly explain the racking.

With only 3 posts that means 1 at each corner & 1 in the middle. The span is thus 12'. What size girders are used & how many (you only mention 2X8 joists, not girders)? 12' is a long span for girders so I'm doubtful that whatever he put up will meet code but tell us what he did there.

Is the house brick or what? If the ledger is resting on at least a 1/2" masonry ledge along the foundation wall then 4' spacing is approved by the IRC code however they require the use of 5/8" hot-dipped galvanized bolts w/ washers, not lag bolts.

If it does not rest on a masonry ledge & the house is not a brick veneer then based on your 12' joist span they would require the use of 5/8" hot-dipped galvanized bolts w/ washers every 1' 8" & 3 12d common hot-dipped nails every 6".

Is it racking you feel or floor bounce? While the use of 2X8 floor joist spanning 12' may meet code (I don't have my code book w/ me to check) you will most likely experience floor bounce.

mike13 and deckman22, thanks so much. I have to wait until DH gets home to answer your questions except one, and that is it's racking AND floor bounce we feel. It bounces when a dog walks across it even. It only racks if when you're standing on it you push on the rail, but we haven't had any of our 70-mph winds yet.

The house is stucco.

I wondered how the letting-in would work, although I sure like the idea. I think I understand your suggestions about bracing, and I know DH will.

This was built before the last inspection, I think, so I don't know how it made it past the code inspector.

Thanks again.

Susanka

The racking you are experiencing is most likely along a path parallel to the house (you should not feel racking perpendicular to the house or you do have problems).

So you need to provide lateral bracing along the outside 24' length dimension where the 3 posts are (again the 12' span between post is probably too much & you will have to add more posts).

Knee bracing is allowed by the IRC code & will most likely be the less obtrusive to your view from the patio. It is not the most robust so be sure to check any local codes given you are in a high wind area.

Otherwise, 2X6 cross-bracing is also allowed & is quite robust. Keep in mind you do not have to make an "X" with cross-bracing. With a 3-post design you could go from the low side on the 1st post to the high side of the middle post & then from the high side of the middle post to the low side of the 3rd post & that provides the same bracing as making an "X" inside one of the bays.

The above assumes the posts are attached properly to the foundation which doesn't appear to be the case if they are just resting on the patio concrete.

I think your best best is to add the 2 posts as deckman suggested thus you now have 5 posts. Pour the proper footings for all 5 posts & attach properly. Then run a 2X6 PT board from the bottom of the 1st post to the top of the 2nd post. Then run another 2X6 PT board from the top of the 4th post to the bottom of the 5th post.

That should prevent the racking you are now experiencing. However, I'm not a structural engineer (electrical yes, structural no but I did stay at a Holiday Inn Express the other night) so I'd run it by your architect or a structural engineer familiar w/ your local codes to make sure it is robust enough but still provides as little obtrusion to your view as possible.

Perhaps the original post misused the term " racking". I do not know for sure. But based on the definition of racking that I use, no one should be on or under that deck nor near enough for any debris from it to hit them. It could collapse at any moment.

Maybe I didn't use the word "racking" correctly. I asked DH if that was the right word, and he said yes, but he isn't an engineer and hasn't even stayed at a Holiday Inn Express!

I went up there just now, despite your careful advice, bus driver, and tried to get it to "rack." It only did it a little bit, that is, moved from side to side parallel to the house, not from the house to the front edge. When my husband and brother-in-law were out there I thought it moved a whole lot more. Anyway, I'll stay off of it until DH gets home and then I can maybe give you experts a more technical explanation.

The dog that was walking across it was a Lhasa Apso who weighs less than 10 pounds, and we didn't feel any racking then, only bounce; but both my sister and I were amazed he could make it feel that way.

It's really odd (to me) because when I walked out on it now I didn't really feel much bounce at all, and I weigh a heckuva lot more than the Lhasa Apso does.

All of the deck construction being together for a month now, it can't just sort of meld itself together, can it? That feels like a really dumb question, but it just seems way sturdier now than it did a week ago.

Again, thank you all so much. I'll take some pix this evening also.

Susanka

Re: "They rest on the concrete patio below".

While I mention above the posts should be attached & proper footings should be poured, I forgot to stress that if the posts are just resting on the concrete patio & not even attached this is also extremely unsafe.

Busdriver, are you saying that no amount of lateral movement should be occurring? I don't think the OP should be feeling the movement but structures are designed to allow for some minimal lateral movement.

Any deck built on wood posts will move some & the higher they are the more lateral bracing required.

mike13, the posts are attached by a metal thing that is on the bottom and goes up the sides a couple of inches. They look like a U.

Installing the deck boards at a 45 degree angle to the house goes a long way toward eliminating racking.

I checked the IRC code book & it does show most 2X8s can span 12' but it depends on the live load, dead load, & deflection coefficient specifications.

For example at a 40 lb live load, 20 lb dead load, deflection coefficient of L/360 then a #2 2X8 southern pine can span 12' 4" but with the same loads a #2 2X8 spruce-pine-fir can only span 11' 6". The code specifies minimum numbers which help ensure safety so while your deck should not cave in because of the 2X8 joists it will most likely bounce a fair bit.

However, a 10 pound dog should not show any floor bounce on a deck w/ 2X8 joists, 16" OC, spanning 12'. Maybe you & your sister had a few too many sitting out on the deck.

I'm glad they used the metal post bases.

rbanks, while you are correct that the diagonal decking does help reduce racking it is not an acceptable solution from a code perspective unless signed off by a structural engineer. Of course, their inspector passed it anyway. Also, most Trex decking is not approved to be run diagonally on 16" OC joists, only 12" OC joists.

No, no, no, no, no, mike13. Neither one of us "imbibes"; my sis's church forbids it, and I would if I could but I can't. I am not exaggerating or kidding -- both of us could feel the dog walk across the deck, and more than once. I'm sure it's hard to believe.

Also, in regard to my dumb question about the wood melding together, we've had a lot of rain this last week -- real downpours, and lasting several hours sometimes. Is it possible wood would swell and reduce racking?

It is certainly theoretically possible but I'm not sure how probable.

The posts could have been real green when installed in the metal post bases, the installers may not have tightened the nuts appropriately, the posts dry out & shrink somewhat such that the the posts can move/lean a little within the metal post bases, & thus the amount of racking is increased.

Another scenarion is the metal post bases could have been manufactured on the high end of their width specification (but still within the min/max specs) & the 4X4 posts on the low end (but still within specs), and the nuts have become loose thus allowing more movement than typical.

However, unless the posts are sitting in a pool of water they do not typically change their dimensions such that you would go from "racking a lot" to "racking very little". The posts are vertical members & thus most the rain is sheened away.

Also the metal post bases typically are not really designed to prevent racking movement however they do help somewhat. It is good to place the vertical plates in-line w/ the direction of the racking plane otherwise the bolts & the friction of the plates are the only things preventing racking at the post base.

Make sure all the post base bolts/nuts are tight.

But, bottom line some type of lateral bracing should have been installed.

Thanks again to everyone. DH came home and, sure enough, the deck racks about a foot or slightly less, best we could tell. From underneath, where I was, the 4x4's rock a little bit in their U-holders on the concrete also. I could also see the deck bounce when he walked across it. He weighs 165. I don't know why it didn't seem to when I tried to make it move.

Just for the record, so you know I'm not crazy, I called my sis; she says her Lhasa Apso weighs 13 pounds, and that when she first noticed the dog making the deck bounce she didn't want to say anything because DH and I are so excited about our new house, but when I noticed it she thought she should tell me she'd noticed it before.

Again, I appreciate all the input, and we are taking it very seriously. Our GC will be back next week and we're going to redo the thing. We feel he should pay for part of it and we'll pay for part of it. 6x6's, cross bracing, and a decent footing.

Thanks! I'm sending all of you some virtual superduper brownies, best I can do.

Susanka

We've spoken with our builder. He says there are footings, explains that they are under the 4X4s but may not go out all the way to the edge of the concrete patio so when the hole appeared we just didn't see them. He says there are deep footings. For the racking, he says he thought that might happen but wanted to wait to see if it did (says the constant working of the wind at the deck caused it) and his plan is to put a heavy metal X under the deck attached to all four corners (and maybe attached elsewhere, I'm not clear on that). The deck is racking about a foot right now. Does this seem like a good plan to you experts? Thanks again for all your input.

I have no confidence in that builder at all. "Thought it might happen"? I would build it initially so that racking would not be a possibility. The newer treated lumber rapidly corrodes many types of metal.

The x bracing sounds decent as long as it covers the entire span.You also might want to mention throwing in some more lag bolts on the ledger,(nothing to do with racking), as 48" seems minimal.The posts being 4x4's and 8' apart would be minimal as well.

Thank you, both. I'll talk this over with DH before we make a decision about the GC.

This makes me nervous for you! Waiting to see? Sorry.

We have a deck under construction right now (2 years after our home was built). A landscaper that we've used on many projects at multiple houses is handling this. He has a masters in engineering, yet he hired another engineer to come out and check the footings and the design plan. The carpenter has worked for our landscaper for 10 years. The building inspector came out for the footings and design plan, too.

Ours is complex as it goes around an oval pool, but ours doesn't budge at all, even with all the complex cantilevering that had to be done. It's probably over-engineered, but we're happy with that.

If you want me to snap some photos of the supports, I can do that after the crew leaves today.

Good luck with this --make sure it's safe. You can replace a deck, but you can't replace people.

Cameron

Susanka, my vote is for 6 x 6's and more of them. At our other house we used 4 x 4's to support a very light weight roof for our deck. The roof was made of 2 x 4's and lattice. It would constantly sway in the wind.

For our new 12 x 16 covered deck we have 5 - 6 x 6's (2 are 20+ ft tall and the other 3 are 12+) They support our deck, stairs and a 12 x 16 foot peaked roof. It is as solid as can be. You can jump on it and it feels like you're jumping on concrete.

I hope it all works out for you!!!

Thanks, you guys. wonbyherwits, if it's easy for you do the photos, I'd appreciate it.

charliedawg, that's what we want it to feel like, concrete.

Our GC said if it had been 8 x 22 (our original plan) it would have been fine, but when we enlarged it he thought the wind might work on it so it would rack. We've really believed in this guy, but this of course just isn't okay.

Dh and I are going to talk it all over tonight and give him our verdict. I don't like the look of the 4x4's and know I'd feel better with the 6x6's, plus the X bracing. I took some pix, couldn't get them to load. Will do that this evening.

Thanks again to all.

Oh and I can snap some pictures of the bottom of our deck from our patio underneath it if you want to compare. Just let me know. :)

charliedawg, that would be great.

You guys are such friends. Thanks again. (charliedawg, I know you're not a "guy"; as a kid growing up in Iowa we called our parents "you guys" even, as well as our friends; don't know if kids still do that! Probably not.

Whoa! I didn't realize how many mud dauber nests were underneath there. Dh is going to be busy when he gets home.

We actually have 3 more shorter 6 x 6's in concrete that I didn't mention before. They are on the stairs and are also set in concrete.

All of the wood you see here are 2 x 8's (other than the deck boards)

Hope this helps.