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ovahimba 07-22-2010 05:00 PM

Stair construction
 
I'm building my first set of stairs, from an upper deck platform to a lower. It will be 14ft long, 36" wide, using four 2x12s. I plan to leave the outer stringers unnotched and attach the treads using metal brackets. The two inner stringers will be notched.

My reasoning is:
1. This will leave the outer stringers stronger.
2. It will weather better with fewer cut surfaces
3. The placement of railing posts will be easier and allow more flexibility.

However most of the stairs I see in my neighborhood have notched outer stringers. Am I missing something?

DangerMouse 07-22-2010 05:18 PM

Most people prefer them that way because of sweeping and snow removal.

DM

Willie T 07-23-2010 07:27 AM

The Mouse is right. For the most part, the wind will keep the stairs clean of leaves and debris if the ends are open. Also, trapped, wet leaves in the corners are not only slippery, but can begin mold (rot).

I'm always curious when I hear of extra stringers on a narrow stairway like yours. Why?

You do realize that the weight carrying is handled by the thickness of the treads and support of the risers under the nosing edge of the treads, right? After a stringer is notched, in essence, all you really have left is little more than an angled 2x4. The code demands 5" left, but it would shock you how many are cut down to a lot less. (Not to scare you, though, most stair stringers cut from 2x12's have over 5 1/2" of good wood left.)

Millertyme 07-23-2010 08:48 PM

Stairs should be framed like everything else and you should always go 16" on center hence the need for the 4 stringers. This is especially true when it comes to composites as they are much more flexible. cut-out stringers are more common than what you intend to do. In addition to what has been listed above, there are a few more reasons. The un-notched stinger do not look as professional as the all open( notched) stringer look. Also, once you have your 1st pattern made it is easy enough to make all 4 the same and assembly is a breeze. no need for cleats or brackets.

ovahimba 07-23-2010 08:51 PM

Thanks for the responses

No, I didn't realize the primary strength of a stairway came from treads and risers tied together.

I assumed adding a middle stringer strengthened the structure. I figured adding two would double that effect. I thought it more of a consideration since the stringers are 14 feet long. If it were only 5 feet I wouldn't have considered more than one middle stringer.

I wasn't planning to have risers, to leave a more open look. As it is I probably need some sort of support in the middle of the span.

Willie T 07-23-2010 09:04 PM

The "more the better" theory on stringers comes from the sad loss of true construction knowledge and skills prevalent with modern day "carpenters".

Click here for dozens and dozens of examples of stairs constructed by people who still understand the basics of sound stairway construction.

Interestingly enough, if you research old stairs, you will rarely find any with more than two stringers. And they have stood the test of often hundreds of years of use.

BTW, that site is a clean architectural and design site called 'STAIR p-o-r-n'.org. Your browser may refuse to take you there. Google those two words (with or without the dashes) and you will find the most amazing stairs built in this entire world. No P_O_R_N involved at all.

Proby 07-23-2010 09:11 PM

Quote:

Originally Posted by Willie T (Post 473919)
After a stringer is notched, in essence, all you really have left is an angled 2x4.

That's what I've always wondered. A stringer with un-notched treads is a 2X12 while notched treads is more like a 2X4 like you said. How does that have enough support? Isn't every notch a weak spot?

I know it's done, but I am wondering the science behind it. You mentioned the treads and risers tied together gives support, but what about when there are no risers?

BTW, your link was edited out by the forum software, the second part of the URL must be a banned word.

EDIT: the banned word is "p0rn", when someone clicks the link they can just replace the "****" with the correct spelling of the word p0rn. I've never seen that word itself censored out before, very odd.

Willie T 07-23-2010 09:18 PM

Quote:

Originally Posted by Proby (Post 474288)
That's what I've always wondered. A stringer with un-notched treads is a 2X12 while notched treads is more like a 2X4 like you said. How does that have enough support? Isn't every notch a weak spot?

I know it's done, but I am wondering the science behind it. You mentioned the treads and risers tied together gives support, but what about when there are no risers?

BTW, your link was edited out by the forum software, the second part of the URL must be a banned word.

EDIT: the banned word is "p0rn", when someone clicks the link they can just replace the "****" with the correct spelling of the word p0rn. I've never seen that word itself censored out before, very odd.

Thicker treads. Treads are often 3" thick for this very reason. The 3" treads also let you pass the 4" 'ball passage' code requirements if the rise is kept to just under 7". This is for open treads with no riser boards.

As for the notches weakening a stringer.... see how many carpenters have the nerve to stand in the middle of a bare 8' notched stringer and bounce up and down. They know better.

See the added text above to deal with the banned site problem. It's really a site worth seeing.

Gary in WA 07-23-2010 09:50 PM

The 2006 Deck Code (which you may be under, check with local B.D.) requires a solid riser if at or over 4” high: Fig. 27

5” minimum of meat left after notching: Fig. 28
7’ max. span for cut stringers with SP.
16’6” max. span with closed stringers, SP.

Notice Fig. 29 and Table 6, also.
http://www.lancova.com/deckinfo.pdf


Be safe, Gary

Willie T 07-23-2010 10:45 PM

1 Attachment(s)
For your viewing pleasure, here is a stairway from that website that uses NO stringers whatsoever.

And they have many, many others that have even less apparent support than this one does. Please get to that site. The hundreds of beautiful stairs will WOW you.

SNC 07-25-2010 11:41 AM

For 36" threee stringers is enough 14' is not that long, more stringers is ok I get a lot of jobs where the engineer calls for 2x6 nailed 6" oc on both sides of the center stringer and one on each side of the outer ones.

Willie T 07-25-2010 06:11 PM

As I will keep reiterating, a 36" stairway needs no more than a stringer on each side. Just a total of two. Why in the world would an engineer call for doubly reinforcing a center stringer if it did much good in the first place?

Go to the website listed, or simply look at the picture I've included (there are hundreds more on that website) and you will see that it is NOT multiple stringers that give the stairway its strength.

Do quit viewing this as though using the band-aid approach of adding pounds and pounds of nearly useless stringers is going to fix anything. Study a little, and learn what stair building is all about.

kwikfishron 07-25-2010 06:26 PM

Quote:

Originally Posted by Willie T (Post 475188)
As I will keep reiterating, a 36" stairway needs no more than a stringer on each side. Just a total of two.

Wow, hope OP isn’t using Trex for his deck stair treads.

Willie T 07-25-2010 06:28 PM

Quote:

Originally Posted by kwikfishron (Post 475201)
Wow, hope OP isn’t using Trex for his deck stair treads.

I hope NO idiot uses Trex for much of anything. :laughing:

THIS PHOTO will show you the ultimate importance of stringers.

SNC 07-25-2010 06:45 PM

Quote:

Originally Posted by Willie T (Post 475188)
As I will keep reiterating, a 36" stairway needs no more than a stringer on each side. Just a total of two. Why in the world would an engineer call for doubly reinforcing a center stringer if it did much good in the first place?

We do it all the time in apartment buildings and assited living buildings. Our stairs are not 36"


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