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-   -   deck strength - your opinion wanted (http://www.diychatroom.com/f19/deck-strength-your-opinion-wanted-157834/)

denemante 09-24-2012 11:50 AM

deck strength - your opinion wanted
 
Hey all - I'm rehabbing a deck to get me through a few more years. All the wood is still quite solid.

It's actually 12 feet wide by 14 out and square, and it's about 10 feet high. It's bolted to the house and stands on three 8x8 support legs with a header. It's 13 years old.

Based on what I've done - it would take a monster truck crashing through the support legs for them fail. So I'm solid there.

But where it attaches to the house - I'm at the mercy of original construction.

There is a 2x10 header (12 feet long) bolted to the house. It lays right over the hardiplank siding. There are 6 bolts attaching this to the house and it's bolted to the header/part of the wall between my basement and first floor. From the inside, I can see the other end of those bolts.

The original builder put a 2x2 ledger at the bottom of this outside header, then notched 2x2 cuts out of the bottom corner of the joists. Then the joists were toe-nailed in.

I don't like toe nailing. So I added heavy-duty L plates (about 3 inches per leg). On the joist they are bolted through. On the header side, they are glued and lag-bolted to the original header (the one attached to the house). These lag bolts are only about 1 1/2 inches long because I didn't want to go through that header and pierce the hardiplank behind it.

This being said - does this seem like a strong and sound way to improve on the original construction, and a good way to prevent the deck from every coming away from the house?

GBrackins 09-24-2012 03:11 PM

This link will provide you with the American Wood Council's "Prescriptive Residential Wood Deck Construction Guide." http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf
This is based upon the requirements of the 2009 International Residential Code, the basis for most state and local building codes.

It is never a good ideal to have siding between the dwelling rim joist and the deck ledger. It should have been removed. See Figure 14 on page 11. Is flashing installed to prevent water that gets behind the siding from working its way down to the rim joist and/or ledger? is the ledger treated?

Table 5 on page 12 provides for the attachment of the ledger to your home. if there is only 6 bolts then I'd have to say your spacing would be approximately 20" center to center, which may or may not be sufficient depending if it is attached with lag screws or through bolts and the material it is connect to.

Toe-nails are good for gravity loads, but not lateral loads. The 2x2 should support the gravity loads, as long as it was not over nailed/fastened and the wood is treated for exposure to the weather. I've never been a fan of cleats and notching of joists. Notching at the ledger should be no more than 1/4 the depth of the joist per Section R502.8 of the 2009 IRC. Notching joists can cause them to split at the notch.

The brackets you installed will help, but should the ledger fail then .......... the deck will fail. I would have probably suggested Simpson A34/A35 angle brackets. http://www.strongtie.com/products/co...P5-A34-A35.asp

With your deck being 10-feet above grade you should have lateral bracing. See Figure 22 on page 14. This will help to prevent the lateral movement of the deck. Wind and people walking on the deck are sources of lateral loads. These loads will act upon the 6 bolts holding the deck to the house and over time can loosen the connections, allow water penetration and can lead to the failure of the ledger-to-house connection. Usually this connection fails when people are on the deck not when the deck is vacant.

I would recommend making this a "free standing deck." See Figure 21 on page 14. By installing another beam and columns about 2-feet from the existing exterior wall you no longer are dependent on the ledger connection to support that end of the deck. You will need to install lateral bracing on all columns as shown in Figure 21.

The depth of your footing would need to meet an frost depth requirements, or the depth of your existing dwelling footing whichever is deeper. Again see Figure 21 for the depth of footing requirement.

Not sure this is what you want to hear, but it's what you need to hear. Hope this helps.

Good luck!

denemante 09-24-2012 05:49 PM

1 Attachment(s)
Thanks for the fantastic response! I'm always one who wants to do things right (and to code). But we have this deck that's as old as the house - who knows what code was 13 years ago.

The lumber was solid, but gut-instinct told me it just wasn't strong enough. In a few years - I'll probably tear it down and build a brand new deck. My goal here was simply to make it safe and sound for the next few years.

I did already install the lateral supports, and another header across the legs, and a 20 foot 45 degree piece of decking across under the deck - and 2x8 bridging across the middle.

Previously, you could go out to the end of the deck and try to rock it - and it would sway probably 1-2 inches. Now - it barely makes a ripple in a glass of water.

So my gut tells me that aspect is OK to get me through the next couple of years.

See the pic attached - that's the header attached to the wall. You can see the ledger board, the joists (originally toe nailed), the original bolt through to the inside, flashing - and my new angled anchors. As noted - the header is over the siding so my angled anchors - they are bolted to that original header with a lag bolt that only goes in the depth of the header.

Inspection of the header and surrounding areas show zero rot or water damage.

I definitely believe the guide you linked to - that's the right way - and the guide I'd use in a few years for me new deck.

But until then - if I invited you and 5 friends over for a BBQ - would you join me on this deck? Or stay off? :)

notmrjohn 09-24-2012 05:57 PM

Gb is on the way, but since he doesn't even know what town you're in it may take him a long time to get there. He will be hungry so best have an entire brisket set aside for him.

BTW, glued metal to wood? What kind of glue?

GBrackins 09-24-2012 06:10 PM

slow roasted brisket or some nice rib eyes .... maybe a slab on baby backs to start off with

glad to help

joecaption 09-24-2012 08:46 PM

Are those through bolted or just laged to the wall?

I never would have spaced them out that far and would have used 1/2.

I agree you used the wrong L brackets. I would have used a GA1 like this.
http://www.strongtie.com/products/co...rs/L-LS-GA.asp

Are you saying you used glue under the L's you installed? Why?

denemante 09-25-2012 09:26 AM

The single bolt out in the header area - that's original construction and goes through to the inside where there's a washer, lock washer and nut. There are 6 of these.

The L brackets - that's me. And where they attach to the header - it's a 1.5 inch lag bolt (I didn't want to go completely throught that header and pierce the hardiplank). I put waterproof Titebond glue into the lagbolt hole.

The whole point here is that the deck is 13 years old, and the joists were simply toe-nailed to that header. As someone noted - that could be an issue if there was sway (which there was) but I seriously fixed that.

So if I did nothing, my deck (like 145 other decks in my neighborhood) would have been "as-is" as it had been for 13 years.

So I used those L brackets to give me some peace of mind for the next handful of years until I tear down the deck.

So my only real question here is not if it's "right", but more whether I can have that peace of mind :)

allthumbsdiy 09-25-2012 08:29 PM

Where do you live? Do you live in an earthquake prone area?

Have you thought about what your future deck might look alike? Would you be interested in making a freestanding vs. what you have today?

If yes, and careful positioning of the footing piers, I would second what Gary said and convert your existing deck to a freestanding deck now.

That way, when you decide to take down and build a new deck, you would already be ahead of the game.

I am not sure I would be comfortable with what looks like a baluster that is supporting the weight, imho.

Good luck.

denemante 09-25-2012 08:48 PM

We live in GA so no earthquakes here.

No idea what a future deck might look like.

The deck is about 10 feet up, so while freestanding might work - it would basically be like a giant table with 8x8 inch legs - clearly long X or sway supports giving rigidity to the legs would be needed. But almost the whole thing is over a patio.

The current legs - they are just out in the grass. I poured concrete footers 3 feet deep per frostline, cemented in huge allthread, then bolted galvanized feet on - which are screwed to the 8x8 legs.

If I were to put another set of legs back by the house - I'm sure my patio is only 3-4 inches think - I couldn't just stand the legs on it. So - I'd need to jackhammer out about 18 inch sections to dig footers there.

The "baluster" that's supporting the weight - that's the ledger board - and from what I've read - I think it's still to code (or was). Regardless, I've effectively helped it out hugely by adding my metal L brackets adding to the toe nails in anchoring the joists to the header (which is bolted to the house).

notmrjohn 09-25-2012 09:25 PM

dene, i think what you have done is just fine. There are "better" ways, but your works.

If you could work some L flashing under next row up of siding and out past ledger we would be happier. Some 3" screws thru "ledger" into "header" would make me happier, Bolts thru metal all the way thru into inside, happier yet. Bolts thru ledger all the way thru, I'm so happy I can hardly stand it. I think every one wanted you to use a longer L angles (vertically) with two screws into joist and header, and on each side of joist, so that joist won't twist, then they'd be ecstatic.

GB, dene is in Georgia, its gonna be pork instead of briskett gettin Bar B Qued. Rib eyes? Who would wanta barBque steaks? You grill those.

GBrackins 09-25-2012 11:07 PM

well I'll bring my corn cooker and we can boil up some peanuts and bar-b-q a hog for some pig pickin'

denemante 09-25-2012 11:07 PM

Thanks Mr. John - my mindset was that the deck is 13 years old - I suppose not that old when considering building standards.

I wanted to put new routed railings on it, some custom flowerboxes (stuff for the wife) and just generally give it a makeover without breaking the bank. Just to get me through the next 2-5 years. A nice powerwash then some new stain. Still planning to use that "restore" product on the decking.

As I got into it - that's when I started all the reinforcement.

As I mentioned elsewhere in the post, there are about 145 nearly identical decks in my neighborhood. I've never heard of a problem - fingers crossed.

So I figured while everyone else was just using their decks as-is - I'd beef mine up a little with the improvements noted. If it was perhaps already "good enough" in the original state - I figured what I did could only help.

To come full circle - a friend in NJ was on a deck that collaspsed with 12 people on it. It was pretty new - and on a $2M house. Go figure. It broke away from the house.

I think any contractor in America would look at my deck now and agree that it's truly rock-solid....with one unknown exception.

That's where I started with this post. The header is bolted to the house with 6 bolts that go through to the inside with nuts/washers on the inside. Seems solid - but what do I know.

Then previously - the joists just sat on a ledger and were toe-nailed in. So all that held the deck to the header were toe-nails. That scared me - so I added my L brackets. But those only attach to that same header with 1.5 inch long, 1/2 inch lag bolts...

So my fear remains that the deck could somehow come away from the house. Maybe it's unfounded fear, based on what I've done.

I suppose the majority of force is straight down....it's not like I have 8 guys running out to the end of the deck and abruptly stopping, "pulling" on the deck outward.

The basement is now finished - so I can't get inside that header area any longer. I wish I could have run bolts through my joist L brackets all the way inside and put a washer and nut on the other end.

The crane comes tomorrow to install my 14 person hot tub on the deck - we'll see how it holds.....just kidding.

mae-ling 09-25-2012 11:39 PM

Ok you got me with that last line

GBrackins 09-26-2012 12:06 AM

good one dene ..... nice job

notmrjohn 09-26-2012 10:04 AM

I saw "crane", I thot;but he's thru working on deck? Then...

Boiled goobers...one of the worst things I ever had in my whole mouth.


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