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How to Build Stair Stringers
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Jan 25, 2024
Stair stringer layouts might seem like a struggle, but with some simple tricks and a little basic math as shown in this video, you'll have no trouble. FREE WEEKLY NEWSLETTER: https://bit.ly/2T3USuy WATCH MORE BAILEY LINE ROAD: Winter Tips - https://bit.ly/2rpnUcm Product Tours - https://bit.ly/2L2H54Q Woodworking - https://bit.ly/2RN83jC Real Rural Life - https://bit.ly/2RI5dvY CHECK OUT MY WEBSITE: https://baileylineroad.com/ My Cabin Building Course: https://baileylineroad.com/cozy-cabin/ How-To & DIY eBooks: https://baileylineroad.com/shop/ SOCIAL MEDIA: https://www.instagram.com/baileylineroad/ http://bit.ly/BLRfacebook https://twitter.com/baileylineroad https://www.pinterest.ca/Canadashandyman/pins/
View Video Transcript
0:00
About a month ago, a friend of mine named John, he's renovating a house in Knoxville, Tennessee
0:06
and he wanted to redesign a staircase leading into the basement. He was having some trouble. Part of
0:12
that trouble had to do with the fact there was a beam in the way and we had to figure out a way to
0:16
get rid of that. But other than that, John's challenge was laying out what are called stair
0:22
stringers, which are the side pieces that actually hold the treads on a stair. And that's what this
0:28
video is all about. I'm going to show you how to use a carpenter's square to lay out stair stringers
0:35
It's really pretty simple once you've seen the trick, plus a few additional things you need to
0:41
know about how to handle the bottom of the stringers and the top of the stringers so that
0:45
it all works out fine on the finished stair. So I've got a piece of wood here. We're actually
0:50
going to lay it out as a stringer, even though it's shorter than it normally would be. But before I
0:55
get to that, I want to show you a little diagram here. I just need to put the whole challenge into
1:01
context. So we've got this. This is the second floor level here. This is the level that we want
1:06
to be able to rise to as we come up the stairs. And this is the first floor level. And this is
1:11
the stringer that we want to cut. Now, most stringers would be cut from 2x12 lumber. This is
1:19
a 2x10 I have here. It's not going to matter at all for this tutorial, but the 2x12 size is
1:25
necessary to give you the strength that you need. Essentially, what we're looking at here is the
1:31
piece of lumber that will support the treads, which would be a piece of wood kind of put on
1:38
here. Those are the treads. And then the risers, which would just be a decorative piece right here
1:46
Actually, the tread is going to extend beyond the riser a little bit. So that's what this wood
1:51
does. And our job here in laying out this piece of wood is twofold. First of all, we need to make
1:58
these cutouts for the treads and risers in the right proportion and equal spacing to each other
2:06
That's where the carpenter's square is going to come in. Once we've done that, we also need to
2:12
modify the stringer somewhat at the bottom on the top. See, what we want is we want an equal rise
2:20
from one stair to the next. So rise is how much you rise when you step on the next stair up. So
2:27
we want that to be the same all the way up. Now, when we're cutting a stair stringer
2:33
in all likelihood, it's going to be resting on some sort of a subfloor, maybe a basement floor
2:38
concrete floor, but it's almost never resting on a finished floor. So one thing to keep in mind
2:44
and I'll get to this later, is whatever finished floor is going to be applied later, the thickness
2:50
of that floor needs to be added to the bottom end of the stringer so that this is equal to that
2:58
is equal to that. So that's one thing to keep in mind. Another thing has to do with the thickness
3:04
of the stair treads itself. Typically, one and a half inches thick. So in order to get
3:11
the rise figure here at the top stair equal to all the others, we need to
3:18
shift the whole stringer down an amount equal to the thickness of the treads so that this is equal
3:27
to that, is equal to that, is equal to that in the finished stair. So just two little modifications to
3:33
keep in mind. But before we get there, now it's time to use the carpenter's square to mark out those
3:38
notches with precision. So this is the square that I'm going to be using to lay out the stringers
3:43
It's not a conventional carpenter's square, but it's going to work just as fine. It's the numbers that
3:48
count, not the thickness of the blade. Now my job here at this stage, your job at this stage actually
3:56
is to mark accurate and consistent rise and run figures on your wood. There's a little formula
4:03
here that you might find useful. When you take one rise figure and you add to it one run figure
4:13
the sum should equal 17 or 18 inches. That will create a comfortable stair proportion
4:25
under foot. And notice something interesting. Using this method, when the rise figure
4:33
becomes smaller, so you have a shallower stair, the run figure needs to become proportionally longer
4:42
for that stair to feel comfortable under foot. And the reverse is true as well. When the rise
4:47
figure gets really high, the most comfortable orientation is to have a short run figure
4:55
So in John's case, we've determined that a comfortable geometry that's going to fit into his
5:04
situation would be 7 and 3 quarter inches of rise and 10 and a quarter inches of run
5:19
So those two together equal 18. Now the trick is to create this geometry all along, one notch
5:26
after another on this piece of wood. Now you might be wondering how I came up with these numbers in
5:31
the first place. I mean it's one thing to have them add up to 17 or 18, but how did I determine
5:38
7 and 3 quarter inches for the rise of each individual stairs? That takes a little bit of
5:44
math and I'll show you that now. A little bit of math and a little bit of trial and error
5:51
So I'm just going to draw this again. This is the floor and this is the wall
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and this is our finished floor. Now it is actually a finished floor
6:09
that we want or you account for the finished floor because basically what we want to do is we
6:14
want to we want to figure out how many stairs, how many vertical rises of a stair can fit into
6:23
the height we've got. So that's the height from here down to the floor down to the finished floor
6:29
on the first floor. Now I happen to notice, know that in John's case he's dealing with 105 inches
6:36
105 inches of total rise. So as you can imagine we want all the stairs to be of equal height
6:45
We can't have seven and a half stairs. We want to have only full stairs. So that's where a little
6:52
bit of trial and error math comes in. So 105 inches. Let's just take a guess. Let's say well
7:01
how do seven, how do how do stairs with a seven inch rise look? So divided by seven
7:09
Oh look at that. That's that's not usual. We have a nice round number. So as it turns out
7:14
if we went with 15 stairs then that would fit evenly into 105 inches
7:23
With the stringer I should point out this is the top of the stringer here. So I'll just draw a few
7:30
notches here. I won't continue on this one. The top of the stringer stops here. So the finished
7:38
floor of the second floor is actually considered to be one of the stairs for this calculation
7:43
purpose. Stair number one, stair number two, stair number three and 105 inches work out to 15 exactly
7:51
As I said that hardly ever happens. It's more like this. Let's say 105 total inches and I'm thinking
7:58
oh let's try a seven and a half inch divided by 7.5. Seven and a half inch rise
8:06
It worked out again. 14 inches. As I said it doesn't normally work out this way. So what you
8:11
need to do is you need to say oh I can fit in 14 and a quarter stairs and I want 14. So I'm gonna
8:19
I'm gonna juggle the rise figure so that it all works out. Basically what is the rise figure
8:27
that when applied to the total height difference between one floor and another
8:32
will equal a perfectly even number of stairs. So the rise figure is the first thing you want
8:39
to figure out. Whatever rise figure you work out, whatever one you determine, you plug it into the
8:43
17 or 18 inch formula and you will get the run figure which is the horizontal width of the stairs
8:52
Now I should mention that when you're building stairs the only given that you have is this the
8:58
only ironclad given that you have is the distance between one floor surface to another and that's
9:05
the one you want to have to work with. Whatever you work out here will ultimately determine
9:11
how far out from this wall in this case the stair stringers go. So normally it's not crucial. I mean
9:20
the stair could end here, it could end here, it could end here, doesn't really matter as long as
9:27
the ratios are correct and I have an equal number of equally spaced stair risers then everything's
9:36
going to work out fine. In other words the the outward extent of the staircase is a function
9:42
of what you do over here with total height and total rise figure and then this is kind of a
9:49
secondary thing that just comes out at the end. So that's how I determine how many that what my
9:56
rise figure is and then now I'm finally going to show you how to translate that to actual wood
10:03
So you might be looking at this drawing and thinking wow all those dimensions, all those
10:09
angles, there's an angle at the bottom, the angle for the stringer itself, the individual angles of
10:15
the cutouts. I mean there's a million ways to mess up on this right? Well there is but there's also
10:23
one way to sidestep all of those problems and that's to use your square. So this is going to be
10:31
my stringer and remember I mentioned a seven and three quarter inch rise. Well seven, seven and a
10:38
quarter, seven and a half, seven and three quarters and you notice that it is perfectly aligned with
10:44
the edge of the wood. So that's what I want on that side and then if we go to the other side
10:49
the run figure there was ten and a quarter. So if you look here ten and a quarter and
11:01
trust me it's perfectly lined up with the wood. So seven and three quarters on one side
11:07
ten and a quarter on the other and that's my angle. So the notch I need to cut will look like this
11:23
So that's the first notch of my stairs and all I have to do to mark the next notch
11:31
is to find ten and a quarter again and seven and three quarters
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I put the ten and a quarter right on the spot where the other pencil mark
11:44
ended and the seven and a quarter over here and I draw it again
11:51
and then I just repeat the whole the whole way up. Now let's say you want, let's say you're the kind of person that that likes little tools that make
11:59
things easier and more precise. You might want something like this and the way they work is
12:05
they're little clamps. They they clamp to the square so that that that automates the placement
12:15
of the square from one one tread to the next. I bought these from Lee Valley Tools which is a great store. I've been buying things from them
12:28
for 40 years more than 40 years and I still have all the stuff I've got from them. It's been well
12:35
worth it. So there now with this in place I don't have to worry about lining up my eye or being
12:41
careful or anything like that because I just go and I position it again. These clamps rest against
12:49
the wood so it speeds the process a little bit. Absolutely ensures that it's going to be
12:59
consistent from one to the next. So I've re-marked this sample stringer with markers so you can see
13:08
what it looks like more closely and I want you to imagine for a moment that this is this is the
13:12
bottom of the stair. So this would be the amount that you add for the decorative rise. Now I've
13:20
left quite a bit there. Other carpenters might just put quarter inch veneered plywood. I like
13:25
to work with solid wood so I put a solid wood amount there for us to see and I mean I won't
13:31
I haven't marked it yet but the stair tread might go on here. It might be this thick or a little bit
13:37
thicker and it's going to extend out past the decorative rise part but what you need to remember
13:45
is at the bottom as I said before you have to make allowances for the finished floor for the
13:51
thickness of the finished floor. So if this is, if this is the thickness of the finished floor that's
13:56
that's the position of the finished floor there. I've just drawn it arbitrarily and maybe these
14:02
stairs go down into a basement and they're going to fasten to a concrete floor. Well that's going
14:08
to be somewhat somewhat lower than the finished floor so you need here you need to extend
14:17
the stringer to make allowances for that because this is going to be the finished floor and that's
14:23
what works out in terms of geometry but the stringer will actually be sitting on a floor
14:27
that's below the finished floor. Another thing you need to be aware of is what's happening down here
14:33
at the bottom and this drawing here shows the bottom this area of the drawing shows the bottom
14:42
of the stringer. Now it's very important that the stringer be securely mounted. It can't move at all
14:49
of course you want your stairs to be solid and one way to help with that is to notch out the
14:55
bottom of the stringer right here so that it fits over maybe a two by four. That two by four will be
15:04
securely bonded to the floor underneath. So basically that the stringer can't slide out
15:12
because the notch fits over the two by four and that prevents the bottom end of the stringer
15:19
from slipping out. So I would cut that detail right here and let's say I'm making it for a
15:25
two by four so a two by four is three and a half inches long and don't forget this surface here
15:35
is the one that I'm going to be making for the bottom of the stringer
15:41
So two by four is inch and a half wide so I'm going to be cutting out
15:47
this part of the stringer. I'm going to be removing all this wood so that I create
15:56
a notch that will keep it secured at the bottom. I need to do something similar almost a mirror
16:02
almost a mirror image of that actually at the top end too. Here at the top end of the stringer
16:08
we have to make an allowance for the thickness of the stair treads so this is basically the top
16:17
of the top most stair in the stringer. It's not the floor which as I said is the floor
16:24
surface is up here and that's essentially kind of the final step but right now this surface here
16:32
is that surface there and since we want a consistent rise figure we need to remember
16:43
that there's going to be a stair tread on here and you'll need to take that into account and
16:47
how you take it into account depends on the thickness and whether or not your measurements
16:55
take you up to the level of the finished floor as they should but you may need to alter this
17:02
position to preserve that all-important consistent rise figure. Now in the same way that we want to
17:11
secure the bottom in a way that can't move we also want to secure the top of the stair
17:17
in a way that can't move so we want another notch. This time though we want the notch here
17:24
so that notch will be big enough to accommodate a 2 by 4 and in this case the 2 by 4 would be
17:32
fastened to whatever wall framing the stairs are resting against and in practice we would
17:39
want to put the the notch right here so we're dealing with the three and a half inches actually
17:47
we don't need to account we don't have the whole three and a half inches in the stringer because
17:51
if we do we're we don't really have a lot of wood up top there even a small notch say a couple
17:56
of inches wide will do us just fine and an inch and a half in depth because that's the thickness
18:04
of a 2 by 4 and then we would we would cut this here we could make this even smaller actually
18:11
looking at it right now this seems a bit narrow here a bit prone to breaking off so maybe we
18:18
would put it down here the 2 by 4 would of course extend looking at the diagram here it would extend
18:25
down below the stair stringer a little bit but that's okay as long as the stringer is resting
18:31
on top of this now not only can the bottom not slide out but the top can't slide down and with
18:38
those two things together you're going to have a very very solid staircase so right here I'm going
18:44
I would be cutting off this of course this is all waste and then this is waste here too
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and we would have this notch in the top now cutting these things is always a two-part process
19:00
the first part involves cutting with a circular saw as far as you can but of course it's a circular
19:07
blade so where the cut might continue right into the corner up here down deeper where the saw blade
19:13
is kind of curving away you're still going to have some wood there so it's a combination of
19:19
using a power saw and then using a hand saw to finish that cut in the corner in a perfectly
19:25
plumb way you'd use that technique here and you'd use that technique here when you're making the notch
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