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Author Topic: U-Shaped Stairs in a Timber Frame  (Read 1626 times)

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Offline jb9

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U-Shaped Stairs in a Timber Frame
« on: June 18, 2017, 08:56:13 pm »
Hello,

I am currently working through my design and thought I would share some progress.  I am designing a 26x32 4-bent Saltbox in which the stairs will be in the center bay.  I have seen another thread on this topic so I thought I would share some of what I am learning.  From my experience, stairs are difficult to master and I have struggled to find something I hope is build-able.  It does seem that a U-shaped staircase in a center bay is a common location for a timber frame so I thought it would relevant to this group in the Forestry Forum.  If there are any master carpenters here who have any thoughts or recommendations, I am all ears.  As far as code, I spoke to the Building Inspector and he wants to see 36" treads as per IRC 2009.  I originally drew a "split level" landing but tried to change it to a flat landing without messing up the door entrance locations and headroom height requirements.  I have a center bay measurement of 80" so my width will be roughly 40".  I just hope I can find a railing solution that will work cleanly.  I have drawn the stringers and framing in order to show how I am working through the problem.

Thanks in advance.



  

  

  

 

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #1 on: June 18, 2017, 09:37:14 pm »
Nice.  How deep is the landing?  It looks to be the minimum 36".  You might want to make it a little bigger to make moving furniture a little easier.  Making it the same as the stair treads (40") would make it seem a little more balanced rather than a bottle neck.  Personally, I'd probably make it 48-50".
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline Don P

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Re: U-Shaped Stairs in a Timber Frame
« Reply #2 on: June 18, 2017, 09:42:33 pm »
Not a master by any stretch but some thoughts. It looks like the top tread of the lower flight is a half step or so, if so why?  I like to rest the bottom of the upper stringer on a solid "floor" of landing, so usually I'll build this area out with a wall or header to fully support under the stringer which has a level cut similar to the bottoms of your lower stringers. I usually develop my sketches from the tops and faces of the finish materials and then work backwards to the framing, it helps me account for different material thicknesses easier.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #3 on: June 18, 2017, 10:44:50 pm »
Thanks DonP and ljohnsaw.  I would like to go wider but I am probably going to keep it as narrow as
possible and have a removable railing in the event I need to move large items upstairs.  I might go up to 42".  The run will most likely stay at 36" due to the door entries at the top of the stairs.  Also, what appears to be a partial tread is actually just my solution to increase head clearance going to the basement by using 2x6's for the landing platform (instead of 2x8's or 2x10's).  I can get a bit more bearing against the stringer by extending it a little and then feathering the extra length into the platform.  Also, that is a good idea to work backwards from the dimensions of your finish materials, DonP.

  

 

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #4 on: June 19, 2017, 09:29:38 am »
What's left of that stringer at the landing is a little scary looking (weak).  Not sure how tall your floors are but how about this?  Move/make the first stair flight 1 or 2 more stairs (move out into the room a couple feet)?  That will increase the height of the landing (and  you could make it deeper) and then the second flight will be a step or two shorter moving away from the bathroom door.  This will also give you more head room for the basement stairs as well as allow a better tie in for the stringers.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline jwilly3879

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Re: U-Shaped Stairs in a Timber Frame
« Reply #5 on: June 19, 2017, 11:32:08 am »
I ran into a similar situation with building inspector on a cabin that I built. He insisted that the stair treads were too narrow and that they had to be 36". The code actually reads that the stairway needs to be 36" wide.

This is from the 2015 IRC but reads the same as 2009.

R311.7.1 Width.
Stairways shall be not less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height. Handrails shall not project more than 41/2 inches (114 mm) on either side of the stairway and the clear width of the stairway at and below the handrail height, including treads and landings, shall be not less than 311/2 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #6 on: June 19, 2017, 11:55:53 am »
Thanks ljohnsaw and jwilly3879.  I am seeing that exact same language in my code (it seems to read the same for IRC 2006, 2009 and 2015).  The interesting part is that the code really only calls out 36" ABOVE the handrail (I will have one).  I am going to "tread lightly" with my building inspector for sure on this one.  I definitely want the stairs to work well.  Good suggestion ljohnsaw.  I will post another drawing tonight with the entry to the bedroom at the top of the stairs and how I can't move the 1st floor stair "run" out 1 or 2 stairs.  I'll see if it can be done though.

Thanks for all the helpful suggestions so far (especially to jwilly3879 for citing that IRC code for other folks reading this thread).  I think getting this detail correct in a timber frame is crucial since bents really can't be moved once a frame is designed and raised.

Here's a shot of my tread (with a 1" nosing) to assess the space available for banisters and newels should I opt for a railing mounted on the face of the tread.  My aesthetic is definitely more rustic/industrial so it would be great to come up with something that might work.



 

Offline Jim_Rogers

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Re: U-Shaped Stairs in a Timber Frame
« Reply #7 on: June 19, 2017, 02:37:34 pm »
J:
When you post a picture with text in it, please increase the size of the font in the picture. I had to zoom in to 133% of the page size in order to read it.
thanks
Jim Rogers
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Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Offline jwilly3879

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Re: U-Shaped Stairs in a Timber Frame
« Reply #8 on: June 19, 2017, 05:12:40 pm »
My stairs went up the gable wall with a cathedral ceiling. The treads were 32" wide and the hand rail was outside the treads. The room it was in was 16' wide so my "stairway" as defined was 16' wide.

Here are so pictures of the cabin. It is in the middle of a 500 acre lot we have been cutting on for 5 years.

 

 

 

 

 

 

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #9 on: June 19, 2017, 06:41:35 pm »
Those are great pictures.  I see what you mean about having a 16' stairway as defined by the code.  I sent off a diplomatic email to the inspector this morning asking him if I'm ok (and citing the code I am using). 

Here's a rendering of the top of the stairs and how I am going to need access to the bathroom AND the adjacent bedroom.  It's close but I think it will work nicely.  This rendering will show why I am hesitant about increasing the run.



 

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #10 on: June 19, 2017, 07:13:19 pm »
No, I guess I didn't explain myself clearly. 

Keep the top landing where it is at as necessary for the bathroom and bedroom doors.  Make that upper flight of stairs 1 or 2 treads less thus giving room for the mid-landing to expand a bit.  It will also raise that landing 1 or 2 steps depending on what you do with the upper flight.

Then, make up for it with the lower flight (extending it 1 or 2 treads) to reach the higher landing.  This flight will move into the main level a little further from the wall.  I didn't see any restrictions there.

This will also raise the mid-landing giving you more headroom for the basement stairs, too.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #11 on: June 19, 2017, 07:43:04 pm »
I do like that idea but the problem I keep running into is that I lose the height requirement.  In this drawing, I basically set the man's height to 6' 8" to show what I mean.  Does this make sense?  When I move the stairs out, I have to move/increase the size of the opening above as well to achieve the 6' 8" height.



 

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #12 on: June 19, 2017, 09:10:30 pm »
Yeah, I get it.  I thought your bent spacing was a bit more than it is... What is the spacing?  You only have two choices that I see - make the bent spacing bigger (and redo all your load calcs :-\ ) or move that bedroom door somehow.  Rotate it 90 and make a funky bump in the corner of the next room?

I went through a lot of iterations to get my cabin plan to work.  I ended up having to do 12' BETWEEN the bents to get enough head room.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #13 on: June 20, 2017, 08:21:55 am »
This is helpful John.  Thanks.  I have been going through those long iterations myself...  I couldn't agree more about some of the complexities when trying to fit a stairway into a timber frame in a way that is efficient and elegant.  It looks like my bent spacing is 11' 4" (outside face of exterior post to inside face of interior post) which are is the relevant dimensional constraint for the "run" of the stairway so that I can get into the rooms adjacent to the center bay.  It's close and will no doubt require a excruciating level of attention when I build it.  The margins between a design and "as-builts" seem scary to me as I want to make sure this detail is correct because stairs are very important for safety.  I have some new drawings I can post later... 

Offline timberwrestler

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Re: U-Shaped Stairs in a Timber Frame
« Reply #14 on: June 20, 2017, 10:01:58 am »
To gain that head height, there are a few options, but the easiest is to add a riser.  The most simple spot is that you can add a riser is in the middle of the U-landing.  You could also change it to winders, or decrease the tread depth. 

I design a lot of stairs, and I wanted to point out that you should draw all of the parts--the newels, rails, balusters, etc.  That way you can ensure that everything works together.  The continuous handrail requirement with the proper clearances can sometimes be tricky.  By the book, the handrail does not need to continue around the landing, but some inspectors like to insist on it.

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #15 on: June 20, 2017, 10:26:35 am »
I do like that idea but the problem I keep running into is that I lose the height requirement.  In this drawing, I basically set the man's height to 6' 8" to show what I mean.  Does this make sense?  When I move the stairs out, I have to move/increase the size of the opening above as well to achieve the 6' 8" height.



 (Image hidden from quote, click to view.)

JB9,
Looking at your measurement:  The code (as I read it) requires 6'8" vertical height.  You can have the nose of a tread just back of the beam and have less than 6-8 and the next stair down gives you the height requirement.  That is what I had to do for my basement stairs.  I really like the suggestion that TimberWrestler has, one riser on the landing perpendicular to the stair runs. 

One other thing I've seen you need to avoid.  I was doing a little work in a historic Victorian.  They refinished the floor, including the stairs.  They had a set up like yours.  Going down, the last tread projected beyond the newel post at the landing.  Looking down, you could not "see" the edge of the tread as all the wood grain blended together.  MANY people stumbled and fell because they thought the last tread was the same height as the landing.  I think it was a combination of camouflage and your assumption that the newel post marked the end of the stairs.  They solved it by putting a little rug on the landing ::)
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #16 on: June 20, 2017, 11:58:38 am »
Thanks Timberwrestler and ljohnsaw.  I do have a version of this staircase with a step on the landing.  From what I understand, this is called a split-level landing.  In terms of safety and comfort, I would say a flat landing is my first choice, a split-level landing is my second choice and the winders are a distant third.  Also, I do think the flat level landing could be the easiest to conventionally frame (with 2x6's running from bent to bent).  I think what I might do is confirm with a rendering that a plumb line from the front face/leading edge of that ceiling timber will give me at least 6' 8".   I will post that rendering with some dimensions.  Additionally, that is good advice Timberwrestler to detail the newels and banisters to confirm the tread is sufficient.  I'm working with a few stair supply places (that have technical support folks who see these details daily).  If anyone knows a good stair supply vendor that they have worked with in the past, that would be great.  I will keep drawing and posting my results .

Offline jwilly3879

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Re: U-Shaped Stairs in a Timber Frame
« Reply #17 on: June 20, 2017, 01:04:16 pm »
As a Building Inspector the most common correction I write is for stairs.

People don't seem to realize how dangerous the are.

Consistent rise and tread width are critical. Variable rise is the most common violation.


Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #18 on: June 20, 2017, 03:59:09 pm »
Thanks for following this thread jwilly3879.  It's helpful to hear the recommendations of a Building Inspector.  I completely agree that stairs are dangerous and really want to get this aspect of the project well-defined.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #19 on: June 20, 2017, 06:45:00 pm »
I think I have some good news to report.  The one tread that needs to clear the tie beam is currently sitting at 6' 10 11/16".  Additionally, joist sizing was solved for the longest span (which this center bay is clearly NOT).  Floor joist is 7 1/4" deep (a 6x8) which means I could certainly down size or chamfer this one floor joist if needed (I know this is not a best practice but this detail is a lynchpin for my model).  Additionally, I could probably apply the 3/8" variance to this one tread if it came to that (definitely a last resort as consistent riser height is most important to me).

Here is a rendering for those folks following along:
 

 

Offline Don P

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Re: U-Shaped Stairs in a Timber Frame
« Reply #20 on: June 20, 2017, 07:54:40 pm »
Quote
The code (as I read it) requires 6'8" vertical height.  You can have the nose of a tread just back of the beam and have less than 6-8 and the next stair down gives you the height requirement.

This isn't quite right. run a line or lay a board down the stairs resting on the nosings. From that line now plumb up to the headbanger, that measurement needs to be 80" or greater.

The visual interpretations download from these folks is good;
http://stairways.org/

Offline ljohnsaw

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Re: U-Shaped Stairs in a Timber Frame
« Reply #21 on: June 20, 2017, 08:00:23 pm »
Quote
The code (as I read it) requires 6'8" vertical height.  You can have the nose of a tread just back of the beam and have less than 6-8 and the next stair down gives you the height requirement.

This isn't quite right. run a line or lay a board down the stairs resting on the nosings. From that line now plumb up to the headbanger, that measurement needs to be 80" or greater.

The visual interpretations download from these folks is good;
http://stairways.org/

That makes sense.  But I didn't draw it that way and they approved my drawings.  I'll have to go back and measure to see if my stairs will actually pass code!
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 64' - using it all to build a timber frame cabin.

Offline timberwrestler

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Re: U-Shaped Stairs in a Timber Frame
« Reply #22 on: June 20, 2017, 09:13:49 pm »
Quote
The code (as I read it) requires 6'8" vertical height.  You can have the nose of a tread just back of the beam and have less than 6-8 and the next stair down gives you the height requirement.

This isn't quite right. run a line or lay a board down the stairs resting on the nosings. From that line now plumb up to the headbanger, that measurement needs to be 80" or greater.

The visual interpretations download from these folks is good;
http://stairways.org/

Yup, Don is right.  You might get away with it with your interpretation, but it's risky.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #23 on: June 21, 2017, 08:12:10 am »
Thanks for the clarification.  I was aware of that line across the nosings.  It's probably better to apply the actual standard.  Given that reality, I went ahead and took a measurement and got 6' 9 3/16" and carried up the angle of the nosing reference line (37 degrees).  I applied it to the beam to see what kind of a chamfer would match and restore the 6' 10 11/16" clearance.  It actually doesn't look like it would be too bad...  maybe a few passes with a block plane.  Ok, maybe a few hundred passes with a block plane.  :laugh:
 


 

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #24 on: June 25, 2017, 07:51:34 pm »
Sadly, it's back to the drawing board on this...  I am working the heights on the descent to the basement and I need a bit more clearance.  I came to this conclusion when I started reading about the minimum required "throat" that inspectors like to see.  "Throat" is basically the meat of what is left on the stringer.  With 2x12 stock, folks like to see ~5 1/2" or perhaps 5" would be fine.  Regardless, I'm going to need a little more headroom underneath the stairs.  I was taking a look at your work timberwrestler and noticed that you have designed a few "housed stringer" staircases.  I'm kind of new to stair design (I have been wrestling with my own model for 2 years now) so I wasn't totally familiar with how to draw one.  I think a "housed stringer" or treads held up by brackets address the stringer throat depth encroachment issue I am seeing with height clearance.  Has anyone here ever designed a housed stringer or a stringer with brackets to address height clearance?

Thanks and I will post some drawings soon.

Offline timberwrestler

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Re: U-Shaped Stairs in a Timber Frame
« Reply #25 on: June 26, 2017, 08:40:31 pm »
jb9,

There are some guidelines for throat (although I've never heard that term), but I don't think there are requirements.  If you need to make it a bit thinner there are a few tricks.  You can always sister an extra piece on the side that hasn't been cut-like a 2x4.  Or you can use engineered wood like LVL or LSL for the stringers.

For more traditional staircases, we often do housed stringers, where the whole stair assembly is wedged and glued together and then set as a unit.  Andy Engel's stair book is really the best modern resource.  I also help teach a class in doing those stairs at the Heartwood School.

Another style that is pretty easy, and that often fits in with timber framing is to use a timber as a stringer, with thick treads sitting on brackets (or fully housed).  These stairs are just 4" pine treads sitting on angle iron.  http://www.uncarvedblockinc.com/architects-additions.  Most of the stringers were just pine timbers, a few were curved waney pieces.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #26 on: June 27, 2017, 08:33:45 am »
Thanks Timberwrestler.  From what I understand, throat is the wood that exists at the bottom of the stringer.  I do think that housed treads or angle-iron treads will work.  I redrew the stringers with 1 3/4" of reveal above the stairs.  Here's what it looks like.  The height gained is very noticeable.  I will have to use 5/4 treads and I may have to increase the size of the bay by 1" or 2".  Not sure yet.  I just want to make sure the bay will work even if I have to sub out the stairs to a master stair builder.

Here is a rendering:
   

 

Offline Don P

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Re: U-Shaped Stairs in a Timber Frame
« Reply #27 on: June 27, 2017, 12:42:28 pm »
Have you checked height from landing platform framing to basement stairs? that looks like the pinch point.

I've lost the pics... well they're here somewhere on floppies but that was 2 computers ago, for heavy timber stringers you can cut out an L in plywood to make a jig that a router base fits inside of and rout out the housings for a set of timber stairs pretty quickly.

Offline jwilly3879

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Re: U-Shaped Stairs in a Timber Frame
« Reply #28 on: June 27, 2017, 12:55:21 pm »
I have made fake housed stairs by cutting the stringer out of 2x12 and then attaching a full 2x12 to the outside of the stringer.

Offline jb9

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Re: U-Shaped Stairs in a Timber Frame
« Reply #29 on: June 28, 2017, 10:29:32 am »
Thanks Don P and jwilly3879.  I doublechecked my height clearance on the landing and it's looking pretty good ~6' 10 3/4".  My basement stairs will probably be 7 3/4" rise and my main house stairs will be 7 9/16" rise which is an acceptable delta within IRC Code from what I understand.  This will also help with the height clearance.  I will probably do a traditional stringer in the basement and use the housed stringer for the main level.  I will post a rendering later this evening.  I may have to use 1 3/4" LVL stock but that's fine.  Regarding the housed stringers, I found some great videos posted by master stair builder Keith Mathewson.  His layout instruction and craftsmanship are excellent.

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Re: U-Shaped Stairs in a Timber Frame
« Reply #30 on: June 30, 2017, 08:11:15 am »
As promised, here's a new rendering.  This is the triple header (plus angle iron) on the last flight into the basement.  Having offset (or uneven numbers) of stairs in a U-shaped stair case does seem to present difficulties in stair opening headers, but I think because my house is so small, I would rather make what I have work than continue to expand the footprint of the structure.  Does this look reasonable for a stair opening header?  3 sets of 2x joists sistered together?

Thanks in advance.