Building Stairs - Dimensions (THE MATH)

0:02 so before we build any stairs there's a few things that we need to know and we need to figure out uh few of the things that uh we need to know are some of the rules I mean there's there's obviously code on building stairs now in my area uh we deal with a few different things uh you should really check with your local area um just to double check that yours are the same uh so for stairs here's a here's a simple drawing and you can see this is the Stringer so that's the wood that's cut out to support the

0:47 steps okay we've got the Riser which is the vertical piece of wood underneath each step and we've got the tread which is of course uh the part that you walk on those are the three main pieces of stair that you need to uh know the terminology for now Headroom is the amount of room that you have when you're standing on the last on the tread that's right underneath whatever the bulkhead is or the ceiling in the level that you're going down to so that's the head room and there's a minimum distance for that in my area at 76 and 3/4 uh it's nice to have at least 80 in

1:35 honestly in our case we're going to have about 7et 84 in so we've got lots of headro Riser height can range from 5 and 3/4 to 8 in in my area so that's the distance from top of tread to top of tread okay uh nosing that's the little overhang right here okay it's the it's the amount of the tread that overhangs the Riser from the front of the Riser forward and generally rule of thumb here is about an inch uh depth of Treads which is basically from an imaginary

2:22 line uh from the front of the riser to front of Riser so basically from here to here here okay and they they like to see that uh minimum 9 and A4 okay so those are kind of some of the main code related regulations that you're going to have to fall into also when you're choosing your stringer material 2 by10 2 x 12s when when you've got this cut out they want to see about three and a half inches of of uh thickness left from the back of the notch of the cut to the underside okay now for most stairs

3:09 they're built correctly uh with the right tread and and riser and everything 2x1 12 is probably most times what people will be using if you're doing a deck set of stairs you might be able to get away with 2 by10 A lot of times there're a little uh more of a rise on each step you know close to the 8 in Mark uh which changes your angle and and everything and usually will give you a little more meat back there left but 2 by 12 for interior stairs is pretty standard um now some of the things we need to know to figure out the whole layout is we need to know the total rise so that's right from the floor back here

4:03 that's right from right down here on the floor up to the top of whatever your uh subfloor is going to be okay so that's your total rise now your flooring can come into play as well here um if you've got uh say hardwood up there which is extra 3/4 of an inch and carpet down here in the basement uh those two will probably end up working out pretty equal so you don't need to make any deductions for that but let's say you have hardwood up there and vinyl plank or laminate in the basement that's only a quart of an inch thick well you've got a half inch difference so you need to uh calculate what that

4:51 difference will be so top of finished floor down here to top a finished floor up there okay in my case I'm going to have vinyl plank I'm going to have the same flooring in the basement as I am up there so my total distance uh from concrete to top of the underlay that's going to be under that flooring up there is going to be my total rise okay so I'm going to measure that maybe I'll take you with me see if we can get you a little closer okay so I'm going to drop my uh tape measure right down to the top of the concrete floor and I'm going to measure

5:39 from basically underside of finished floor at the basement to underside of finished floor on the main floor okay so that means I'm going to have 38 of an inch more on top of this uh 3/4 inch plywood here because that'll be my subflooring under the under the flooring upstairs so I've got when I'm sitting there I've got 103 and 58 to the top of this plywood so when I add my 38 for my subflooring that's going to go under my floor my finished floor that'll give me 104 in total rise I'll just double check it on this side it should be the

6:31 same yeah within a 16 an inch there okay so now I know my total rise is going to be 104 in okay um something you should always check as well is that the floor that you're going down to is level so the the height here if the floor isn't level at that end if the floor at the end where the stairs land is higher or lower than it is down here that's going to throw your measurement all out so just double check with the level that you're the same and if not just make an addition or or a subtraction at that end so if that end was higher than here by quarter inch then you need to take a quarter inch off your total rise because your total rise is really

7:19 from this point to all the way down there where the stairs land right so if the floor that you're landing on isn't level that isn't going to work out okay so we've got 100 4 in total rise okay uh width widthwise here uh I'm going to be putting half inch drywall on here I've already got half inch drywall on this side so let's just see what we have for a width we've got 37 and 38 yeah 37 and 38 so - half an inch is 36 and 78 I'm going to just make my stairs at 36 in that way there's no fighting to get them in my

8:05 flooring can be finished right to the wall afterwards anyways the flooring that goes on the stairs so if there's a slight gap of a quarter inch or 15 16 or whatever uh well not 15 16 but uh4 inch to say 38 on each side most floor you can just make that work out anyway so okay so I'm going to go 36 in wide for my total stair width um now my uh with with these measurements I can go and figure out how many risers I'm going to have which will give me how many Treads I'm going to have you always have one less tread than risers and uh we can figure out where

8:53 our last tread ends up underneath our bulkhead down there and make sure our head room is going to be all right okay so I've already worked out the math so we had our total rise of 104 in so 104 divided by 14 I just took a rough guess I originally divided it by 133 but that gave me too big of a rise so then I went up one more Riser so 14 was my guess 104 divided by 14 risers gives me 7.43 in which is 7 and 7 16 well that falls in our in our comfort zone for what our Riser Heights can be and it's it's pretty comfortable step

9:41 honestly so we're going to use 7 and 716 and 14 risers now I already said we're we always end up with one less tread than we do Riser so that means we're going to have 13 Treads the tread material I have is 11 and 1 12 in wide and I'll show you that in a few minutes it's a pre-manufactured tread um so when I deduct my nosing off there which is an inch I'll have 10 and 1 half inch Treads or my run will be that okay so if I have a 10 and 1/2 inch run on every tread which was 13 Treads that's 1362 is my total Run Okay so that's my

10:26 my distance from so my that means my stair set of stairs is going to run right from that surface up there to the end of the last Riser is going to be 1362 in okay so now we've got our total run of the stair case let's see if it works out down here so I swung you to the other end now so the where the top of the stairs is going to be as right over top the camera so we've got 136 in from that point back just behind the camera to the end of our step now that ends up coming out basically exactly uh so that

11:11 um our last step is just past this wall okay so top of step is going to be down in this range right here and I know that because I know how many uh Rises I have which is two Rises so I can mark that on the wall measure down from my this is what my head room's going to be this is where I'm going to hit my head when I come down so right from there down to that Mark we've got basically 7 fet so 7 feet is 84 in uh in my area I've only got to be uh 67 and 3/4 or sorry 76 and 3/4 so we've got plenty of room like I said before 80

11:58 head room is nice it's better for moving furniture and stuff but check your local code to see exactly what minimum is for you you can always have more can't have less okay so it looks like that's all going to work out um so we've got all our information now to go and be able to start laying out the the Treads and cutting them I'm going to show you the material okay so here's my materials this is my pre-made stair tread so let's see I think it's an inch thick where are we here yeah so I'm 1 inch thick and I'm 11 and 1 12 in

12:46 wide okay so that's all going to work out these are the 2x 12s that I'm going to use uh to cut my stringers out of when I calculated it out I probably only needed 14 Footers but they only sell uh 16s and 10 I believe in my area so obviously have to make them out of one solid piece so I got 16t 2x 12s and we're just going to get ready to show you how to mark them out so go and check that out we'll have a link below