The plot thickens...

[dortoh]

Well I have a new issue. I just found out that I can't attach the deck as I hoped. The desired attachment point is a cantilevered overhang, so it looks like I have to go freestanding. The issue this introduces is there is a sliding glass door and windows below the deck and obviously I can't have support post blocking them. There could be a post in the center at the outside of the deck but not next to the house. My issue is I'm not sure what size beams, joist and footers I need to span the distance needed. I have included a diagram to help clarify my issue. Any ideas and or suggestions will be greatly appreciated.

http://lh5.ggpht.com/_GdhVWYI6y58/S_WviSqaNzI/AAAAAAAAAOg/sT9xAjVXXfY/s512/deck2.jpg
View larger here:
http://lh5.ggpht.com/_GdhVWYI6y58/S_WviSqaNzI/AAAAAAAAAOg/sT9xAjVXXfY/s800/deck2.jpg

[HappyGreg]

Just a thought for you:
If the cantilever is not that large, it might be worth calling a structural engineer. I have done this several times and the engineer will make a site visit and then if the cant. is acceptable he writes a letter to the building dept and you are home free!, Except for about $200 poorer, maybe the HO will spring for it if you just explain the situation to them.
Or
You could put 4 posts across the back and straddle the door.

Footings within 5 ft of the house foundation should be at same dept of foundation, which probably be deep. 12"x36" for the outside ones would be good here in Colorado, you might be different based on frost depth, just call and ask the depth that the build dept requires for a deck.

FYI: 12 joist span [2x8 will go 13' at 12"oc and 12' at 16"oc]= beam is 2-2x10 at 9' span, 2-2x12 at 10' span, this is based on #2 hem fir, doug fir and SYP are stonger. Draw it up and submit to the building dept and they will usually calculate it all and then tell you what they require if you are not right.

Have a good day!

http://www.centennialdecks.com

[CJ-8_Jim]

A few months ago I was in your shoes designing a deck. If you PM me your email address, I'll send you some proscriptive guides on designing a deck that is in accordance to 2009 IRC (International Residence Code) which US municipalities base their local building codes from.

All these resources's websites were referenced by the helpful members on this forum (sorry, I can't remember the websites or forum threads).

To answer your question, there are a couple of ways to go. Some tips to start with to maximize beam spans (distance between posts) around your sliding door and windows:

(a) Cantilevering the deck joists over the beams (say by 2') will reduce your joist spans and maximize beam spans. Also by cantilevering the deck joists along the house, you ensure your deck's footings are on undisturbed soil (not backfill for the house) and you reduce the chance that your flared (or "bell-ed") footings will interfere with the house's footing.

(b) If the distance from lower level's finished walking surface to the top of the deck is great enough, you should use the widest beams you can (say 2x10" or 2x12") to maximize beam spans.

Option 1:
Using 2-2x10" as beams and joists of EITHER 2x10 or 2x8 on 6x6 posts, you could run three beams:
- beam #1 of 2-2x10 cantilevered 2' from the house
- beam #2 of 2-2x10 down the middle (at 6') from each end of deck
- beam #3 of 2-2x10 cantilevered 2' from the end of the deck opposite the house.

This will allow you to place your posts at a maximium 11'10" apart. Since you don't want to block the window and door, you'll have to figure how to place the posts. In all likelihood you'll probably have 3 or 4 posts per beam with one of the posts placed strategically between the sliding door/widow and the second window.

Option #2:
This is technically feasible and meets code. It reduces your posts to 2 posts per beam and provides the LEAST obstruction of posts. It allows you to go an incredible maximum of 17'5" (and let the beam overhang the posts 9" on each end to get to your 19' deck width).

BUT YOU NEED BEAMS constructed of 3 (THREE) 2x12 (TWELVES)....
Not 2 2x10 as above.

Use 3-2x12" as beams and joists of EITHER 2x10 or 2x8,. By using 3 2x12s sandwiched together over 6x6 posts, you could run the three beams at the same locations:
- beam #1 of 3-2x12" cantilevered 2' from the house
- beam #2 of 3-2x12" down the middle (at 6') from each end of deck
- beam #3 of 3-2x12" cantilevered 2' from the end of the deck opposite the house.

Now you only can go an incredible maximum of 17'5" (and let the beam overhang the posts 9" on each end to get to your 19' deck width).

[John Hyatt]

Wait a sec.....this is a 12' x 19' project right??


A 19' span is less than a garage door header that has joists/rafters landing on it. Standard deal with those is a double 2 x12.

If I was biding that thing ( and I dont understand the need for a cantilever at all I would flush frame) JonMon would....place 4 footings, land the 6x6 posts on the footings, Make up three double 2x12 beams 19' long or so with construstion adhesive,1/2'' cdx,clamped together fastened with griprite screws, another two beams 12' long.

Land the two 12' beams on the 6x6, same with the two 19 ' beams, install the last 12' beam in the middle of the span with joist hangers ,these can be bought from any number of places but I get my steel guy to make them up from 1/2'' steel flat stock welded on both sides just to get the permit store guy happy,joist in with 2x6 16'' on center you can go larger joists but whats the point? its less than a 6' span. Use hangers on all the joists and metal conectors on all post beam conections.

Bang Bang....done. John Hyatt www.deckmastersllc.com

[dortoh]

Greg,
The cantilever is only 12". I wish I could place more post along the house but It's almost all window. The HO doesn't even want the 2 post along the house but I have convinced him that they won"t be in the way. I can come in about 1' towards center on the post but that's about it. I will contact the local build dept about the footings.

Jim,
I will PM you with my email address. Based on your recommendations I have come up with a revised plan that I think will work. I will present it to the HO tomorrow.

Here is the revised framing plan:
http://lh3.ggpht.com/_GdhVWYI6y58/S_rWoWGHD6I/AAAAAAAAAOw/UmeH0GeFc3E/s512/deck3.jpg

Larger
http://lh3.ggpht.com/_GdhVWYI6y58/S_rWoWGHD6I/AAAAAAAAAOw/UmeH0GeFc3E/s800/deck3.jpg

John,
I am having a hard time following your recomendations. FYI... the cantilever is the preexisting where the deck will adjoin the house.

How does the revised plan look? Additional input is appreciated and thanks all for the help so far.

[CJ-8_Jim]

Wait a sec.....this is a 12' x 19' project right??
A 19' span is less than a garage door header that has joists/rafters landing on it. Standard deal with those is a double 2 x12.
John Hyatt www.deckmastersllc.com

I do understand your point about garage door headers... My 40 year old home has a 2-2x12 header over a 16x7 garage door... but that header is protected from the weather. I'm not sure what today's code on garages would allow/require... maybe additional additional truss blocking?

I gave just prescriptive guidance (that will keep him safe and legal if a local inspector has a literal interpretation of 2009 IRC). An engineer might/could approve a different design.

According to 2009 IRC, the max 2-2x12 span allowed (with max 6' joist spans) is 13'11". The max 3-2x12 span (with max 6' joist spans) is 17'5"
These PRESCRIPTIVE guidelines comes from the American Forest & Paper Association publication "Prescriptive Residential Wood Deck Construction Guide - Based on 2009 International Residential Code"

[CJ-8_Jim]

dortoh - yes, that is what I was thinking.

Technically you could put the corner four posts all the way in the corners (without a cantilever)... this is what I think John Hyatt is getting at. But like I said in my original post:Also by cantilevering the deck joists along the house, you ensure your deck's footings are on undisturbed soil (not backfill for the house) and you reduce the chance that your flared (or "bell-ed") footings will interfere with the house's footing.

Regarding cantilever on the 19' side furthest from the deck, I guess that's just my personal preference... setting it back from the end allows you a margin of error when drilling piers & setting your frame on top of the beams. I think an overhang of 1'-2' looks better. Plus the piers (i'm using 12" dia) are under the deck and not sticking out.

Got your PM... I'll send you those prescriptive deck design resources and some other construction articles (e.g., from Deck Builder Magazine, Journal of Light Construction, Journal of Fine Home Building).

Heads-up... the magazine articles are good stuff because they show "best practices" that will at times exceed IRC.

[RobertCDF]

A roof is WAY different than a deck... Usually the loading requirements of a roof are 30psf and a deck is 60 psf, that would be the reason for a (2) 2x12 spanning a garage door header. Here you will only be able to use that header on a gable wall with a structural gable. Not to mention the fact that you don't walk around on your roof and have parties on it all the time like you do a deck.

I would never put my name on a 19' span with (2) 2x12's even if the joist were only 4' long.

Hire an engineer. We on a regular basis modify cantilevers to support a deck load (in fact we ripped the bottom off one today to modify it tomorrow) If your engineer is uncomfortable with that idea then have him spec an outdoor rated glulam beam to clear span that 19' it can be done easily and will probably be a 5 1/2" x 14 (then you won't need one in the midspan) This will all depend upon your local loading requirements.

[John Hyatt]

Thats one way to look at it Rob, another way would be to look back at what has already worked that being a double 2 x12 span garage door header 20' in use for hmmmm80 years or so. Also dont forget the snow load working on these things.

My name is on several upstairs projects done exactley the way I mentioned out 10 years or so they seem to be working just fine. I add the plywood not for strength,although it adds a little,but to keep the pt lumber stable those griprite screws are adding a lot as well. Covering the top with rubber flashing keeps the weather out.

Adding another 2 x 12 adds weight and in the real world not really that much more span power no matter what the little book says. Outdoor gluelams are not that at all when you read the fine print they are rated for undercover use not to be exposed to the weather a person would have to retreat them with Termin-8 as well as rubber flashing to even give the thing a fighting chance.

John Hyatt www.deckmastersllc.com

[CJ-8_Jim]

A roof is WAY different than a deck

I would never put my name on a 19' span with (2) 2x12's even if the joist were only 4' long.

Robert,
I feel like your post and critical remarks are directed at me... was that your intention?

If so, please take the time in the future to actually READ posts.

If you go back and re-read my post, you'll see that we are in agreement.

[CJ-8_Jim]

Wait a sec.....this is a 12' x 19' project right??


A 19' span is less than a garage door header that has joists/rafters landing on it. Standard deal with those is a double 2 x12.

Bang Bang....done. John Hyatt www.deckmastersllc.com


John - Why do you believe a double 2x12 is sufficient for a 19' span?

Robert appears to disagree with you.

I disagree also. I believe 3 2x12s are necessary if you want to try to span up to a max 17'5" with max 6' joist spans

[John Hyatt]

There are always different ways to get to the same place in Counstrustion.

For me I go with what I have already done, for some others they go look in a book for how to do it. Like I said I have several upstairs projects done exactley the way I said I did.

There are millions of houses with double 2 x12 garage door 20' headers doing just fine. As a ex framer for 10 years or so I know the amount of detail we put into those headers, hit it with the nailgun and put it up. You have to figure the rafters,joists,the strongback and the roof supports are all dependent on that header not to mention the weight of the plywood roofing and 3' of snow.Building a beam like I do is way stronger than any of those headers.

The mid span hanger I use is made up from 1/2' steel and bolts thru with loctite.

But Man!!! go with a tripple or for that matter build the beams from 6 2x12s if it makes you feel better. John Hyatt www.deckmastersllc.com

[RobertCDF]

Using 1/2" steel to make a hanger that is nailed (or bolted) to anything less than 7 1/4 x 18" glu lam is a huge waste of time and money, the wood will fail way before the hanger and I mean 100,000# earlier.

Also we go back to the roof thing again, there are way different applied loads to a deck than a roof.

Just because something has been done before does not mean it was right. There is a reason why they require higher loadings on a deck than they do a roof.

[John Hyatt]

So Rob,those hangers cost me $15 per with a strong coat of black primer out the door that I back up with good ol rustolium rattle can. What are you paying for the store bought able to handle that load? that has the wow impact with the Wallet and the permit store.

Weight and Wiggle Rob, weight and wiggle, how do you see it diffferent with a roof or a deck.

Just because I did it and it worked defentley means its right. J.

[RobertCDF]

You really think the "wiggle" that happens on a roof is the same as the "wiggle" that happens on a deck??? Really??? So you make a regular habit of putting large tables that weigh 150+ lbs and a grill weighing the same, and 15 people dancing to music on your roof???

And your right there has never been anything done that sat fine for years and then just failed one day out of the blue because something was not done right, even though it seemed right because it stood for so many years... I think I heard of a bridge doing that... 1967-2007 lasted for 40 years, it must have been right... then what happened?...

[ArtDeck-O]

Robert,
I feel like your post and critical remarks are directed at me... was that your intention?

If so, please take the time in the future to actually READ posts.

If you go back and re-read my post, you'll see that we are in agreement.
He comes off that way towards everyone he disagrees with from what I can tell. It's his way or the highway apparently. There's more than one in every forum I visit....sad.

[Andy Engel]

I wouldn't be comfortable with a 19 foot 2x12 beam, either. And while John is right that such beams have been used in the past for garage door headers, what really matters is what the code says today. I can't find anywhere in the IRC that allows such a span.

I too would look at a treated lam or psl beam. Around here (Connecticut), the supplier will do the engineering for free. John is also right that such a beam should be protected with a waterproof layer. I would argue that all beams should be so protected. It's cheap insurance. I would consider bituminous membrane (BT 25 or Vycor). Ice and Water Shield would work, too, as would torch down membrane. All of these are self healing, so the nail holes between the joists and the beam wouldn't leak. Another option is a steel beam, which again, my supplier would engineer.

Another option that wouldn't require engineering is to open the cantilevered floor from below and run the deck joists back to the mudsill. You'd then need to re-insulate the cantilever, and carefully detail where the deck joists exit the cantilever to keep water out.

[dortoh]

OK, I met with the homeowner yesterday and presented the options of 1. bringing in an engineer and 2. the revised framing plan. He wants to continue without the engineer for now keeping that as a last resort. We reviewed the plans and he liked them with a few exceptions. If possible he wants to maximize the head room in the main part of the under deck area and wants the post at the end of the support beams. I told him I would see if I could make that happen.

Here is what I have come up with. I think this will work but just not 100% sure. Could I make the rim joist continuous? Is the cantilever on the outside beam excessive? If it is I was thinking I could reduce it and add a third post in the middle of the beam (see plan). Or make all the joist continuous and keep the center beam under the joist.
http://lh5.ggpht.com/_GdhVWYI6y58/S_7VRLe6oaI/AAAAAAAAAO8/2VMoHOKGvb4/s512/deck5.jpg

View Larger:
http://lh5.ggpht.com/_GdhVWYI6y58/S_7VRLe6oaI/AAAAAAAAAO8/2VMoHOKGvb4/deck5.jpg

What do you think?

Also how much pitch if any do you guys usually put in your decks?

Thanks again for all the help

[John Hyatt]

I wouldn't be comfortable with a 19 foot 2x12 beam, either. And while John is right that such beams have been used in the past for garage door headers, what really matters is what the code says today. I can't find anywhere in the IRC that allows such a span.

I too would look at a treated lam or psl beam. Around here (Connecticut), the supplier will do the engineering for free. John is also right that such a beam should be protected with a waterproof layer. I would argue that all beams should be so protected. It's cheap insurance. I would consider bituminous membrane (BT 25 or Vycor). Ice and Water Shield would work, too, as would torch down membrane. All of these are self healing, so the nail holes between the joists and the beam wouldn't leak. Another option is a steel beam, which again, my supplier would engineer.

Another option that wouldn't require engineering is to open the cantilevered floor from below and run the deck joists back to the mudsill. You'd then need to re-insulate the cantilever, and carefully detail where the deck joists exit the cantilever to keep water out.

Thanks Andy.

I really did not mean to come off like my way is the only way.

I do a little more to that beam then I mentioned. Installing camber is a little trick I use if you were able to see Criss--BoneSaw-- post on the pro site I do something like the way he installs curved stairways, bending wet pt 2x12s,Camber up in the middle.

Also the conection with the hanger mid span is protected from bolt run out, that is as the stress is layed on the weak point>> the bolt holes<< I have a way to protect that area and keep it pretty close to the over all stress of the beam.

I know what I do works and over here in Cow Town ,its different than say New York. Anyway its good to get a lot of info one way or the other I respect all you pro builders. John

www.deckmastersllc.com

[RobertCDF]

He comes off that way towards everyone he disagrees with from what I can tell. It's his way or the highway apparently. There's more than one in every forum I visit....sad.

Considering I was AGREEING with CJ-8...

And your still mad about something that I said where I even said IT WAS NOT DIRECTED to you personally. Just blanket statements. There are quite a few guys making these statements not just you.

[CJ-8_Jim]

Dortoh -
Technically you just miss IRC with the post placement on the top and middle beams. Max code beam span in that setup is 17'5" (assuming #2 PT yellow pine) -- your top and middle beams with two 6x6 posts have a span of 18' 6.5" (or 13.5" too much).
- Will it stay up? Most likely.
- Is it code? No.
- Will it flex at some point in the future? Who knows.. maybe... maybe not.

I like blocking between the joists... can't go wrong with blocking... it's easy to do at little cost. This will help fight future flexing.

No problems with the lower beam when using the optional third post.

I noticed you narrowed the deck to 11'. You could keep it at 12' if you want. You can also get rid of all the joist cantilevers and just do joist spans of 5'6" or 6' if you'd like.

If I were the HO, I think I'd prefer beams cantilevered 9" (max beam span 17'5") with NO optional posts (i.e., just 2 posts per beam).

Yet another possiblity if views are obstructed... does one side have less obstruction than the other side? Maybe you could cantilever beams on one side by 1'7" o.c. and have posts flush on the other side?


http://lh5.ggpht.com/_GdhVWYI6y58/S_7VRLe6oaI/AAAAAAAAAO8/2VMoHOKGvb4/s512/deck5.jpg

View Larger:
http://lh5.ggpht.com/_GdhVWYI6y58/S_7VRLe6oaI/AAAAAAAAAO8/2VMoHOKGvb4/deck5.jpg

[ArtDeck-O]

Considering I was AGREEING with CJ-8...

And your still mad about something that I said where I even said IT WAS NOT DIRECTED to you personally. Just blanket statements. There are quite a few guys making these statements not just you.

Not mad....your posts have a certain tone to them, one I don't care to see in forums where people are just trying to share information. I know exactly what you meant in your post in the other thread...same thing you meant is a few on this thread. Your view of other people's opinions is very low when they don't match yours....simple as that.

[ArtDeck-O]

That frame is going to be rock solid. The cantilever should be fine since you have 2x8's on 16's. And yes, you can make the outer joists one piece....I would do that as well, not only for looks but also for a little added strength.

[RobertCDF]

Not mad....your posts have a certain tone to them, one I don't care to see in forums where people are just trying to share information. I know exactly what you meant in your post in the other thread...same thing you meant is a few on this thread. Your view of other people's opinions is very low when they don't match yours....simple as that.

Well I am sorry that I come across as abrasive against opinions "that differ from mine" When really I am trying to come off as a WARNING against opinions that are DANGEROUS and may result in personal injury or death to someone.

Sharing information is great but when the information is flawed and may result in injury then I am going to "rudely" disagree. Maybe it is ok maybe the span just barely holds the load and maybe everything will be fine, then maybe they will sell the house one day and the new homeowners add a small hot tub and suddenly disaster strikes. I have seen on numerous occasion where people have just plopped a hot tub down on a deck without reinforcing.

[dan]

Dortoh,

If the cantilever projects only 12", why not extend the deck joists into the cantilever section and attach to top plate. You must block bewteen but this would allow you to remove the posts that are standard with the free-standing deck.

Dan