Deck stringer layout

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Old 08-13-19, 09:51 AM
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Deck stringer layout

So i want to make sure i get this right, my first time laying out stringers. I have 8'11" total rise. and i have a total run of about 10'10" . I have 2x12x16 to cut them out of and in my research i found that i could do 14 rises of 7 5/8" and 10" runs to put me at about where i need to be. 15 rises would put me well onto my existing concrete which is where i'd like to be. my questions are;

1) can I cut 15 rises of 7 1/8" out of that 2x12x16? this would put my bottom of the stringer completely on the concrete. if i only do 14 rises it only goes about 2" onto the concrete

2) the information i've seen online for 14 rises of 7 5/8 also shows where you take about an inch off the bottom one, so not sure if i need 14 at 7 5/8 and then the shorter one or just 14 rises total.

Thank you in advance
 
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Old 08-13-19, 10:33 AM
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Here is a pic of the current stairs, There was a wooden landing at the bottom that I removed and filled in the concrete. I want them to end at the concrete with 14 rises or with 15 they will go onto the concrete.

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Last edited by PJmax; 08-14-19 at 11:32 AM. Reason: resized picture
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Old 08-13-19, 05:46 PM
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Number one, verify that the height you are measuring is from where the steps will land. An easy way to do that is to lay a 12' 2x4 on the top deck landing and put a long level on top of it, support that 2x4 vertically where the stringers will end (measure down to the concrete) with a stud... put one screw in them where they cross so that you can adjust the 2x4x12 up or down it until it's level. Then measure down to the concrete pad from THAT point.

14 rises at 7 11/16 will put you at 107 5/8. (15 rises at 7 1/8" is 106 7/8.) Your final 14th rise can either be your last step up onto the deck, or if you mount the riser flush with the top of the rim joist, you will have the last tread flush with the decking. You need to know that because it will move your stringer landing 10" one way or the other depending which way you do it.

I would suggest you just draw it out in order to picture it correctly. You cut every riser the same, even cut an extra one if needed, because cutting it to length is the next to last thing you do.

The very last thing you do is cut your bottom rise shorter by the thickness of your tread... and account for any variation or pitch on your pad as you trim the bottom of the stringer so that your bottom tread will still be level even if the pad isn't. And hopefully nothing varies by more than 3/8" from side to side on that bottom step.

If you do go with 15 risers at 7 1/8, you would probably want to drop the stringer down below the rim 8 1/8" so that the last step is onto the deck. That would mean you have 14 runs (140") as measured horizontally from that attachment point to the front of your stringer, wherever that may be.
 
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Old 08-13-19, 06:52 PM
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I measured it out with a boards, string level and tape measure, it's definitely 107" rise. I have one stringer laid out at 13 rises of 7 5/8" and the bottom at 6 5/8". Mounted where the current one is, it should be onto the concrete pad below. So I think I am good there. Edge to edge on current stringers is 36". I'm planning to put Trex boards on them so wondering if I need 4 stringers instead of 3 and with these long stringers do I need any mid support on them? The left stringer will be screwed to the 6x6 and right side will have a 4x4 Midway down.
 
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Old 08-13-19, 07:07 PM
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According to the DCA6 figure 28 (free download, just Google it) a cut 2x12 stringer's maximum span is 6ft. So yes, you would need header support across the midspan of all 3 (or 4) of your stringers. (See the DCA6 section- stair requirements)

IMO you don't want to stray from Trex's installation instructions, which I assume for your product is 16" on center. (Not 17 1/4" on center... but that's awfully close)

Whether you go with 3 or 4 stringers, one challenge is making them all exactly the same. You might enjoy reading my comments in another recent thread where I discuss how I like to do that. It's post 5 in the thread below.

https://www.doityourself.com/forum/c...stringers.html
 
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Old 08-13-19, 07:23 PM
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Ah, good read. Mine is 7 5/8 and 10" runs. I'll figure out the hypotenuse tomorrow and I did buy stair gauges for this purpose($2 and some change on Amazon, no brainier) I'll look up that DCA6 though. That's the issue with the current setup, not enough support and previous owners never maintained it.
 
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Old 08-13-19, 07:25 PM
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It's a weird one, that's for sure.

the hypotenuse would be just under 12 19/32.
 
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Old 08-14-19, 04:30 AM
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Ah yes, i had seen the DCA6 figure before but didn't read the title of the document i was looking at, my county references it for building code. I do see the ' in there. i'll be 10.5-11' so i'll plan on putting a 4x4 in the middle of the right side anyways. putting a footer in for it, running it up and bolting it to the right side stringer and then having 3' stick up for my post sleeve to go over. So does that mean i need a post on my middle stringer too? or can i just run a 2x6 across the 4x4 and screw to the 6x6 on the other side?
 
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Old 08-14-19, 04:48 AM
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They would probably rather see a 2x12 if you do a single.
 
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Old 08-14-19, 06:09 AM
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Yea i could do that, not sure how much difference it makes. I do need to get another 2x12 to put around the stoop anyways.
 
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