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Old 05-23-2013, 02:42 PM   #1
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Stair Blocking - Why did they do this?


Hi. I have 3 questions I hope people can answer. Pictures attached.

1. Does anyone know what the purpose is of the blocking on the back of the stairs that are in my house? They are glued to the wood and the treads are glued to the top of the risers. The risers and treads are also glued to the 2 stringers. 4 or 5 screws also fasten the bottom of the riser to the back of the tread. Do the blocks add structural integrity or do they better connect the riser to the stringer, or both? The treads and stairs are hickory, btw.

2. I am making another set of the same stairs with 3 steps, also in hickory, but the stairs will be 11 feet wide. How many stringers would you suggest I use? I was thinking one on each end and 3 in between, so for 132 inches wide the stringers would be 33" apart (ie 132/4). Or, should I use 4 in between making them 26"+ apart (ie 132/5) ?

3. I am using hickory for the treads and risers. Do you think 1-1/4" finished is sufficient thickness or should I go with 1-1/2"? The existing ones are 1-1/2" but one side is exposed whereas neither side will on these 11' wide stairs. Hickory is an expensive wood, which is why I am asking.

Thanks so much
Attached Thumbnails
Stair Blocking - Why did they do this?-2013-05-23-15.23.59.jpg   Stair Blocking - Why did they do this?-2013-05-23-15.24.20.jpg   Stair Blocking - Why did they do this?-2013-05-23-15.24.46.jpg  


Last edited by Toronto; 05-23-2013 at 04:36 PM. Reason: grammar
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Old 05-23-2013, 02:49 PM   #2
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Stair Blocking - Why did they do this?


Please go back and add your location to your profile.
Those stairs would not be legal in the US.
No over hang, no rounded nosing, even the run and rise looks off.
Those look like factory built stairs.

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Old 05-23-2013, 03:35 PM   #3
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Stair Blocking - Why did they do this?


Quote:
Originally Posted by joecaption View Post
Please go back and add your location to your profile.
Those stairs would not be legal in the US.
No over hang, no rounded nosing, even the run and rise looks off.
Those look like factory built stairs.
Thanks for your input. Sorry, I thought I had my location recorded and have updated it. I am from Toronto, Ontario, Canada (just like my screen name!).

I am surprised these stairs would be illegal in the US. But, to get any discussion about these stairs being illegal (at least in the Province of Ontario, Canada), they fully conform to the Ontario Building Code (OBC), the drawings were approved by the City of Toronto Building Department and the final construction was also been inspected as conforming by my local Toronto Building Inspector. Specifically, the OBC lays out the following:

Section 9.8.4.2(1) of the OBC specifies for rectangular treads, which these are, a maximum rise of 7-7/8" (200mm). These are 7-1/8" so they conform. For the run it specifies a minimum of 8-1/4" (210mm) and a maximum of 14" (355mm). These are 8-1/4". Again, they conform. Section 9.8.4.3.(2) further specifies that for rectangular tread the tread depth must not be less than its run and not more than its run plus 1" (25mm). The treads are 9-1/4" deep. Again, they conform. You may not notice from the picture but the riser is slanted backwards by 1" from the vertical where it meets the tread at the bottom. That results in the leading edge of the tread above being 1" proud of the bottom of the riser, ie a 1" 'overhang'.

For leading edges of treads the OBC does not required them to be bevelled or rounded but Section 9.8.4.6 specifies that where they are bevelled or rounded it must not reduce the depth of the tread by more than 5/8" (15mm) and in no case exceed 1" (25mm) horizontally. These treads do have a 1/8" round-over, which may not be visible from the picture. Again they conform.

So, you see, these stairs conform in every way to the local building code. I really wonder what building code requirements they would violate in the US?

Also, by 'factory built' it seems you are suggesting a big box company supplied them or something, but they were built by a well-respected company in Southern Ontario that specializes only in high-end custom stairs. This company, nor myself, would ever dream of allowing stairs that do not conform to the local building code to be installed, nor would the city building department approved the plans or the inspector approve the installation.

With that out of the way, is anyone able to answer my questions?

Last edited by Toronto; 05-23-2013 at 03:38 PM.
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Old 05-23-2013, 03:48 PM   #4
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Stair Blocking - Why did they do this?


the blocks are their for gluing and fastening purposes.. by doing it that their are no visable fasteners in the face of the tread
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Old 05-23-2013, 03:51 PM   #5
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Stair Blocking - Why did they do this?


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the blocks are their for gluing and fastening purposes.. by doing it that their are no visable fasteners in the face of the tread
Thanks. I would have thought that the treads themselves being glued to the risers and the risers and treads being glued to the stringers would have been enough but I guess not. Good to know.
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Old 05-23-2013, 04:27 PM   #6
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Stair Blocking - Why did they do this?


We, over the years, have let ourselves get (or been forced into being) kind of ridiculously warped about Building Codes.

1007.3, as opposed to 1009.3 stairs, or Group I-3 requirements... or whatever someone thinks of next.

Often so different, and non-compliant with one of the other codes..... Yet, are not the same humans, with the same legs and feet, traversing all these sets of stairs?

Sometimes makes you want to look at the AHJ, and just say.... "Really?"
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Old 05-23-2013, 05:06 PM   #7
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Stair Blocking - Why did they do this?


Quote:
Originally Posted by joecaption View Post
Please go back and add your location to your profile.
Those stairs would not be legal in the US.
No over hang, no rounded nosing, even the run and rise looks off.
Those look like factory built stairs.
Actually you can't simply state this would 'not be legal in the US' as stair residential building codes is a municipal regulation in the US and thus it varies by state and tow. But, as a general rule in the US the riser height is specified as being a maximum of between 7 ¾" & 8 ¼" and some areas specify a minimum of 6". So, my stairs comply even with this US requirement. The run, not including the nosing, is in general in the US between 8-1/4" and 14". Mine is 8-1/4", so it conforms. Most US building codes require the tread, which is the run plus the nosing, to be 9-1/4" to 14". Again, mine complies. As for the slope of the riser in relation to the vertical US codes do not appear to disallow this, but specify that the step riser slope (out of vertical) must be less than or equal to 30 degrees measured from horizontal surface of the tread). Mine is 8 degrees, so it again complies. There is no requirement for a traditional nosing other than the that created by the difference in tread and run length. ie you can meet the requirement by having a slanted riser or a traditional nosing. There also appears to be no requirement for a rounded leading edge in on a tread but where it does occur the radius of curvature should not be greater than 1/2 to 9/16 inch, depending on where you are located. Also, in general, the leading edge should not project more than 1.25 inches and not be less than 3/4 inches.

Of course the codes could vary just a bit by municipality and state, but there is a good summary of the general US requirements for both stairs, guards and handrails at http://inspectapedia.com/Stairs/Stair_Codes.htm

Anyway, not only do my stairs meet the building code but contrary to what joecaption stated they are also legal in the US. I think we have to be careful on here with making statements like this. Yes Willie T I agree with you that we are all pretty well the same humans with the same feet and the codes do indeed appear to reflect this, at least as far as stairs go, in their general uniformity.

Last edited by Toronto; 05-23-2013 at 05:10 PM.
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Old 05-23-2013, 05:18 PM   #8
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Stair Blocking - Why did they do this?


I'm guessing the lack of handrail means that this is a as yet to be completed stair. I'm hoping that the underside of the stair will be covered, which still doesn't explain the screw holes on the cantilevered portion which appears will be exposed....

To answer your question a general rule of thumb for cut stringers is 3 for 36", 4 for 48", etc. but there is more to it. The stiffness of the wood, the thickness of the wood, the throat thickness, method of attaching treads & risers, etc. At the last Stair Manufactures Association meeting a team from Mississippi State University gave a spreadsheet based presentation on stringer load-bearing capacity and deflection, there are many things which the effect strength of a stair. Given the cost of materials you may want to contact a structural engineer.
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Old 05-23-2013, 05:49 PM   #9
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Stair Blocking - Why did they do this?


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I'm guessing the lack of handrail means that this is a as yet to be completed stair. I'm hoping that the underside of the stair will be covered, which still doesn't explain the screw holes on the cantilevered portion which appears will be exposed....

To answer your question a general rule of thumb for cut stringers is 3 for 36", 4 for 48", etc. but there is more to it. The stiffness of the wood, the thickness of the wood, the throat thickness, method of attaching treads & risers, etc. At the last Stair Manufactures Association meeting a team from Mississippi State University gave a spreadsheet based presentation on stringer load-bearing capacity and deflection, there are many things which the effect strength of a stair. Given the cost of materials you may want to contact a structural engineer.
You are right. The stairs are not yet completed. The underside will be covered. The wall to be built on the underside of the stairs beside the cantilevered portion will be located a bit proud of the stringer such that the drywall when it meets the riser will cover the screw, leaving about 1-1/4" of cantilevered portion showing. I designed it this way as I wanted to be able to see the zig-zag of the stairs from the side. But I do wish they had located the screws a bit closer to the stringer so I could have left about 1/2" more of the treads and stringers exposed.

Hickory is about as hard a hardwood as is ever used for residential stair treads. I just remembered that 1-1/4" thick hickory was what they were originally going to use for these stairs but I specified 1-1/2" for aesthetic purposes, given they are seen from the side. The stringers on these stairs are fastened with screws and wood glue which is about as good as you can get. They are 36" apart but this is because the wall to be built under the stringer that is beside the cantilevered portion contributes to the structural integrity of the assembly. They told me otherwise they would have used 3 stringers (but I think they should have used 3 anyway).

I think I will just go with 1-1/4" thick treads and risers, glued and screwed with glued blocking just like in the pictures. I'll have a stringer every 16" and (using 1-1/4" thick stringer material) as these stairs are in a great room between a dining area and sunken living room and during a party there might be a number of people standing on it. That's more than double the stringers I was going to originally use, but stringers are cheap as are a few extra screws and more glue and so is my labour (me!). Also, no matter how many I use the cost of the hickory treads and risers is the same. So, that's 9 stringers (132/16 + 1). I think it might be overkill but I'd rather have a big safety factor built in even though it's only 3 treads (4 steps down).

Last edited by Toronto; 05-23-2013 at 05:55 PM.
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Old 05-23-2013, 05:53 PM   #10
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Stair Blocking - Why did they do this?


I am going to stand next to Joe on this one. I am surprised those stairs are legal anywheres. The craftsmanship looks great, the design looks like some one who has very little experience.
The stringer looks undersized, there should be 3 stringers.
They should have 3/4" subfoor installed and then the stair treads and risers.
The width of the stars, the rise and run looks wrong.
I am sure I would find other items if I was there looking at them.

Is no way I would expect those to last going from the first floor to the second floor if that is their purpose, would be suicide Trying to hand truck furniture up them.
Might be fine for a kids play house
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Old 05-23-2013, 06:04 PM   #11
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Stair Blocking - Why did they do this?


Sounds like you will certainly have a strong enough stair. The important part is both tread and riser are glued together. The screws are there in a clamping function and do little after the glue has dried. With the riser glued on both faces it acts something like an I-beam adding greatly to overall strength.
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Old 05-23-2013, 06:18 PM   #12
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Stair Blocking - Why did they do this?


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I am going to stand next to Joe on this one. I am surprised those stairs are legal anywheres. The craftsmanship looks great, the design looks like some one who has very little experience.
The stringer looks undersized, there should be 3 stringers.
Not if you are using hickory and where the wall underneath the exposed stringer (yet to be built) also supports the stringer. I just looked at the drawings and they were stamped by a structural engineer, and approved by the building department.

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They should have 3/4" subfoor installed and then the stair treads and risers.
Maybe if you are using a less dense wood, but not for hickory. Maybe you have never worked with hickory but hickory treads and risers can be stiffer than other woods with a subfloor. A subfloor is only sometimes required under the treads if you are using a wood that is not as hard as hickory.

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Originally Posted by funfool View Post
The width of the stars, the rise and run looks wrong.
I have proven with my measurements that they fall within both the Ontario Building Code and US codes. Did you read all the information I gave above giving the actual measurements? Doesn't look like it.

As for stair width, the Section 9.8.2.1 of the OBC states that the stair width of exit stairs measured between wall faces or guards should be not less than 2'11" (900mm). These stairs are 3'2" wide which is more than ample, taking into account the guard which will be on the one side. That also falls well within US code requirements.

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Is no way I would expect those to last going from the first floor to the second floor if that is their purpose, would be suicide Trying to hand truck furniture up them.
Might be fine for a kids play house
It's easy to make silly statements like you just did without quoting any measurements, any codes, no reference to the tread and riser material or supporting wall. I think the structural engineer who stamped these drawings, the building department which also did and the inspector who inspected them knows better than you do.
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Old 05-23-2013, 06:37 PM   #13
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Stair Blocking - Why did they do this?


I was going to go back and edit my post, I was writing it at same time you were writing your last post with the details, I did not get to see them before I posted.

I went back and looked at your photos again. I really must have a issue with depth perception today, those look like 3/4" treads and risers, no way it looks like they are 3' wide, I do not believe those look like 2"x12" stringers.

There is a code for how much you can remove from the stringer. At the point of the stringer where the tread and riser meet to the bottom of the stringer is the weak point. You are required to have so many inches there, again to me, does not look like you have enough meat there.

The main point is, the engineer put his stamp of approval on the plans and is all that is needed.
I am man enough to say I was wrong and excuse me, working outside all day in the sun and just got home ... maybe another cold beverage and my depth perception will come back
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Old 05-23-2013, 07:24 PM   #14
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Stair Blocking - Why did they do this?


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I went back and looked at your photos again. I really must have a issue with depth perception today, those look like 3/4" treads and risers, no way it looks like they are 3' wide, I do not believe those look like 2"x12" stringers.
The treads and risers are 1-1/2" thick hickory, not 3/4". They are 3'2 wide.

Quote:
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There is a code for how much you can remove from the stringer. At the point of the stringer where the tread and riser meet to the bottom of the stringer is the weak point. You are required to have so many inches there, again to me, does not look like you have enough meat there.
If there is a structural wall supporting the stair, which there is in the design (not yet installed) on one side, the code goes out the window. It simply doesn't matter as you can't get better support than sitting on a wall. On the other side the stairs are supported by a stringer which is also nailed into the each of the wall studs. The stringers are 32" apart on center. Structural engineers stamp or not, which this does have, the structural integrity of these stairs is more than enough.

Anyway, this is all a discussion I did not expect to get into. I was merely asking about the blocking on these stairs and the 11' wide stairs.
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Old 05-24-2013, 06:54 AM   #15
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Stair Blocking - Why did they do this?


Toronto;

The blocking behind the stairs is a traditional way of reducing the tendency of the stairs to squeak. They are usually glued and screwed on.
But mostly they are found on stairs with thinner treads and risers, and usually those made of softwood rather than hardwood. Seeing the thickness and the material yours are made of, I would assume they will be overkill, and that the joiners who made them were just accustomed to doing that detail.

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