Deck Design Input: Apron Stair

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Old 01-11-09, 11:37 AM
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Deck Design Input: Apron Stair

I'm designing a deck to build as a DIY'er this Spring, and would appreciate any input on my evolving design. The deck will be a single level, ~27" high, probably joist-on-beam using 2x10s for both (built-up beam), supported on top of a very short set of ~6" 4x4 posts on poured foundation piers.

A bird's eye view of the current (rough) plan:



As you can see, I'm planning a fairly large apron stair centered on a short 45 ear removed in the corner. Here are three successive views starting with stringers, adding treads, and then risers:





A few questions regarding this design:

1. Is this the simplest stringer layout? The double stringers each have 22.5 rise face cuts, but are mirror images of each other. All "straight" stringers are identical. So there are only 3 (or 2) versions.

2. Is this sufficient support for 5/4 or 2x decking material (probably cedar or PT)?

3. I'd attach the straight stringers to the rim joist with joist hangers. How should I attach the doubled stringers? Recall they are at a 45 corner in the rim joists, and are each at a 22.5 angle from the one to which they attach. In the ideal world there would exist a double joist 45 specialty hanger, but I have not seen one.

4. I'm trying to connect stair posts to rail posts in a continuous railing. Can the top post be notched on two sides, and bolted to the rim joist and stringer?

5. I'm thinking of attaching the stringers to a 2x6 PT board which will be buried in gravel. Will this be sufficient to keep them level and square to each other?

Thanks very much.

JDS
 
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Old 01-11-09, 07:00 PM
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Wow, those are some really good graphics. What did you use to do them?

There are only 1 thing that I would change. Instead of 6" 4x4s on top of the footers, I would have them come up through the floor and use them for the railing as well. Hang the 2x10s between the posts. That way you don't need a ledger board. You can come out an inch or two. That will stop water from collecting and rotting the wood. In some areas, the deck being attached to the house adds to the taxes. So that's another benefit.

That is not my design. I built a lot of decks with a carpenter who always used a ledger board but the last one I did was on my own and I had to follow an architect's drawings.
My question was, don't have have to connect it to the house for support? His answer was you can build that deck in the middle of nowhere and it will stand alone with no problems.
 
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Old 01-11-09, 07:14 PM
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Thanks for the thoughts. I use Google's free Sketchup tool for the model. I considered free-standing, but that would create a lot more foundation work.
 
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Old 01-12-09, 05:36 AM
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I'm with Pulpo, you can do my drawings anytime. As he said, I have always liked to have my 4x4 posts extend up through the decking and use the same posts that support the framing in your railings. This makes for a very stiff railing and also brings the entire railing system back inside the plane of the deck. It looks a lot nicer. The only thing you can't do is run 2x2 spindles down onto the deck box which I don't like anyway. Essentially, you're hanging the deck on the posts. I put 2- 1/2" carriage bolts in each post.
Your stairs look fine. You really don't need joist hangers to connect the stringers to the deck. Just toe nailing. I'm not exactly sure about the codes, but here in New York they want the stair bottom supported on concrete. We usually build a box that extends under the stairs and out at least 12" in front, with an 8" rise to the first step. This can be faced with bluestone. Like I said, I'm not sure of the code involved, all building departments seem to handle this differently and this covers all the bases. They won't accept a 2x6 buried in gravel here.
 
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Old 01-12-09, 10:40 AM
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Thanks, Craig. I suppose this means the beam must be flush with the ends of the joists (i.e. no cantilever).

I had planned for a bottom rail in any case.

Also, you do lose a bit of deck real estate (it's a small deck). Do you notch the posts for a (sandwiched) beam? Beam-on-post just seems so much more structurally sound to me.

In the "post through the deck" method, what about foundation-less posts? Do you just build a little box for them inside the outside joist and bolt them on? That would certainly simplify the corner posts (which wouldn't need a special corner notching and angle backing).
 
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Old 01-12-09, 03:25 PM
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You don't have to notch the posts to hang the beams on them. There are double joist hangers that fold inwards to hang on the posts. Make sure you use the zinc plated since they have changed the chemical in pressure treated wood. All posts get a footing.

All the footings are installed the first day with the brackets that sit in the cememt. You can start building the next day.
 
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Old 01-14-09, 04:22 PM
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I'm a bit confused about the joist to beam connection in the setup you mention. You're essentially omitting the beam, and instead hanging the joists in plane with a doubled rim joist, which is itself hung off each and every fully foundation-supported post? That sounds like a lot of digging!

Thanks
 
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Old 01-14-09, 05:33 PM
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Not all your railing posts need to extend down to footings. Your perimeter is doubled and your joists are flush framed to that girder with Tecos. It really is pretty simple. You mentioned that one problem you had with bringing the railings back inside the deck was that your deck was relatively small. Why don't you square off your deck, losing the diagonal, and pick up what appears to be about 50 sq.ft. Not as cool looking but easier to build, less waste, and more bang for your buck.
 
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Old 01-14-09, 05:46 PM
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jdtsmith,

Your call on what size of a joist to use. When I build a deck (I'm a deck contractor), I use 2X6 PT joists and install an additional beam due to the reduced span. (My choices of PT joist mat'l is 2X6, 2X8, or 2X12 -- 2X10 would be a special order and would cost about 40% more than a 2X12.) And ALL of my framing is done with ACQ PT -- posts, beams, and joists.

As far as the post to beam connection, Simpson makes BC's for using a 4X4 post to support a double 2X beam -- BCS2-2/4. You are probably on the right coast and can't get a 4X whatever for your beams, so a dbl 2X is what it is. Your beam is in place -- lay the joists on top of it.

What you are showing in your drawings is the simplest way to frme the steps. Use LU hangers (LSSU210's) to support the stringers that are perpendicular to the facias that are square and LSSU210-2 hangers for the ones that occur at the 45 degree corners. Get a Simpson catalog!! (Simpson Strong-Tie - Helping to Build Stronger, Safer Structures or 1-800-999-5099) It'll show you everything that you'll need.
 
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Old 01-15-09, 12:53 PM
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Thanks for the input.

@Craig: The 45 coming off the ledger is there both for aesthetics, but as well to provide access to that #[email protected]% electrical feed box owned by the power company you see at left. So in your continuous post design, the posts would be 3" from the outside perimeter of the girder/doubled-rim-joists, i.e. 4" from the edge of the (1" overhung) decking?

@lefty: Thanks for the hanger references! When Simpson's says "Skewable", do they mean it can be wrapped around a corner? Each corner turns 45deg. Would the corner have to be "dog-eared" to accept such a hangar? Here's a closer look at the stringer detail, from above:



I'll have to visit the lumber yard to check availability, and go through my design again. I've added some detail to the framing. While you're looking, can you comment on my doubled outside joist concept seen at left in the figure below? It is designed to accommodate the 45 "ledger extension" to support the shorter joists beyond the ledger proper. I've switched here to 2x8's: max joist span is 12'3? The short "stub" joist on the left is there just to square off the corner (still not sure what to do about the "stub" railing above it).



Looking at this, it occurs to me I should move that "full length" post on the ledger extension over to avoid interfering with the rail post, and possibly notch it and bump it up in size to a 6x6. It's also possible I should double the outside joist all the way to the beam. Not sure how to make that connection solid. If cutting wood were as easy as drawing in 3D, I could carve out a 6x6 to perfectly hold both sides.

Thanks again.
 
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Old 01-15-09, 04:50 PM
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jdtsmith,

Like everybody else, I LOVE your detailed drawings. We can "SEE" what you are talking about. We'll ALL have to figure this one out!!

By "Skewable", Simpson is usually talking about being able to change the angle of the underside of the hanger to compensate for variations in the rise and run of the steps. Where your stair stringers are perpendicular to the facia, that works. But where your stringers meet at the 45's of the facias, I would suggest just using a side plate (Simpson LS50, LS 70. or LS90) that is skewable to the side and installing a block UNDER the stringer to keep it from settling down.

You have a good design, you doing everything right, and you were clever enough to figure out the Google Sketchup tool to post the drawings. Building the deck and looking at things as you go to find the strongest way to assemble it shouldn't be a problem for you.

One area wher you are going to have to get creative again will be where the 45 degree angle occurs on the stair treads. At the top it's not a problem. Your stringers will be really colse to the 45 degree corner. But as you go down, the span of the deck board on the tread is going to increase. You may have to set a post where the 22-1/2 degree angles and start the process all over again, or incorporate some sort of bracing to keep the tread boards from becoming overspanned.

You'll just have to look at it as you are building it and do what I do -- see issues as they arise BEFORE the boards are attached and get creative enough to say "let's do 'this' to prevent 'that' from becoming a problem". Posts, bracing, slocking, all-thread, getting creative with Simpson products, ... whatever it takes to make it solid and stable.
 
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Old 01-15-09, 07:11 PM
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3" from the outside of your double and 4" from the decking edge is correct with a 1" overhang on the decking. It's a nice detail.
 
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Old 01-15-09, 09:56 PM
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Thanks. I had no CAD experience before picking up Sketchup. It's really extremely intuitive, and there are great online video tutorials, and drawing is fast and fun. You can learn the basics, and then add groups and components, and you're ready to go for simple deck designs and more. A new version was just released. Did I mention it's free? No, I don't work for them, just a happy user.

I'll be sure to check in again as the plan progresses.

Thanks again.
 
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