Stairs Designin and Building

8/11/2019 Stairs Designin and Building

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Designing and Building StairsStairways can be minimal or very elaborate, but

they're all based on simple geometry and accurate finish work

by Bob Syvanen

oday, few people can afford the time anexpense of building classical 19th-centu

stairways. Tastes have changed too, and asresult, stairs have become simpler. But tprinciples of stair design and construction athe same as they've always been, and so athe skills that the builder must bring to ttask. If modern stairs aren't ornate, they sremain a focal point of a houseyour workout there for all to see.

One of the problems builders face in cutti

stairs is getting rusty. Unlike the master stabuilders of the past, on-site carpenters tycally build only a few stairways a year. Fornately, designing a stair and laying out t

stringers uses the same language and cocepts as roof framing. Fitting treads and rers, on the other hand, is nothing more th

simple, if demanding, finish work.

Basic stair typesThe simplest stairwaya cleated stairway, which relies on wood metal cleats fastened to the carriages to suport the treads. You could use a cleated staway for a back porch or cellar, but count repairing the ever-loosening cleats. Wocleats are typically 1x4s, and screwing thein is a big improvement over nails. But angiron cleats will last longer.

Another open-tread stairwayone withorisersuses dadoed carriages. The treahave in. or more bearing on the inside faof the carriages, and they are either nailed

screwed in place. I use a circular saw, and the depth of cut to half the thickness of carriage, to make the parallel cuts. Thenclean up the bottom of the dado with a chisA router and a simple fixture built to the stpitch and clamped to the carriage will also a quick, neat job.

In the past, dadoed carriages were usmostly for utility stairs for porches, decks athe like, but more and more I'm asked to buopen-tread oak stairs that have to be neafurniture quality. One type, the stepladd

stair, can be used when limited space doesallow any other solution (for more, see p. 6

On finished stairs, the dado is usuastopped (that is, its length is limited to

Stairbuilding in its highest forms requires tconceptual skills of a roof framer, and the ting talents of a cabinetmaker. But simple optread runs like the basement stair at left onrequire understanding the basics.

T


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width of the tread), and squared up at the endwith a chisel. If you begin the dado on thefront of the carriage, leave the tread nosingprotruding slightly. If you start the dado at theback of the carriage, the treads will be a littleinset. They can look nice either way.

Other stairways use cut-out carriages. Thesimplest of these is a typical basement stairwhere the rough carriages are exposed, andrisers are optional. The most complicated is ahoused-stringer stairway. It is based primarily

on patient and accurate work with a router.The stringer is mortised out along the outlineof the treads and risers with a graduatedallowance behind the riser and tread loca-tions for driving in wedges. Adjustable com-mercial fixtures or wooden shop-made tem-plates are used to guide the router. Althoughthe first stairway that I built by myself on myown had a housed stringer, I won't try to givecomplete instructions here.

A finished stairway that still requires pa-tient finish work, but is much less tedious tobuild, uses cut-out carriages hidden below thetreads, and stringboards or skirtboards as thefinish against the stairwall. The treads and ris-

ers are scribed to the skirts. The example I'llbe using to describe final assembly is one ofthese that also has an open side, which uses amitered stringer. This side of the stair re-quires a balustradehandrail, balusters, andnewel postsbut that's a separate topic.

Designing a stairwayNo matter whatstyle stairway you want to build, the designfactors that you'll need to consider are com-

fort, code, safety and cost. Comfort gives theideal conditions for good walking, and codedictates what you can and cannot do. Safety islargely a matter of common sense, and costlimits your grand ideas.

Although comfort is very much a subjectivenotion, there are three objective factors toconsider in designing a stairstair width,headroom and the relationship between theheight of the riser and the width of the tread.Of the three, stair width is the easiest to dealwith. Most building codes require utility stairsto be at least 2 ft. 6 in. wide and house stairsto be 3 ft. from wall finish to wall finish, but3 ft. 6 in. feels a lot less restrictive. However,if the stairway gets beyond 44 in. in width,most building codes require a handrail oneach stair wall.

Headroom is not quite as simple, although

most codes agree that basement stairs need aminimum of 6 ft. 6 in., and house stairs needat least 6 ft. 8 in. This measurement is madefrom the nosing line (for a definition, see

headroom in the glossary on the next page) tothe lowest point on the ceiling or beam above.A lack of headroom is most noticeable when

you're going down the stairs, because you arewalking erect and bouncing off the balls of

your feet. Ideal headroom allows you to swingan arm overhead going downstairs, but thisrequires a clearance of nearly 7 ft. 4 in. Head-room can be increased by enlarging the sizeof the stairwell, decreasing the riser height, orincreasing the width of the treads (tread

width is the distance from the front to therear of the tread).

Certain combinations of riser and tread aremore comfortable than others. Most codes setlimitsa maximum rise of in. and a mini-mum tread width of 9 in.but these are basedon safety, not comfort. A 7-in. rise is justabout ideal, but it has to be coupled with theright tread width.

The timeworn formula for getting the treadwidth and riser height in the right relation-

ship is: riser + tread = (a 7-in. riser + a-in. tread = in.) Another rule of

73.5, which is close enough). Still another for-mula is: two risers + one tread = 24 in. I'vealways found the first formula the easiest. Allof them establish an incline between 33 and37. This creates a stairway that is comfort-able for most people.

More considerationsEach tread shouldproject over the riser below it. This projec-tion, or nosing, should be no more than in.and no less than 1 in. In open-tread stairways,a tread shouldn't overlap the tread beneath it

by more than in. The nosing adds to thearea where your foot falls, but doesn't affectthe rise-run dimensions. The top of a handrail

should be between 30 in. and 34 in. above thisnosing, with a -in. clearance between thehandrail and the wall. If the top of the stair-way has a door, use a landing at least as longas the door is wide.

Keep in mind that people aren't the onlythings moved up and down stairs. I once livedin an old Cape Cod house that had a stairwaywith -in. risers, -in. treads, and not toomuch headroom. You could negotiate it if youexercised a little caution, but moving heavyfurniture up and down was another story.

The size of a stairwell is based on the riserand tread dimensions, and on how muchheadroom you need. A typical basement staircan be gotten into a rough opening 9 ft. 6 in.long by 32 in. wide. A main stairwell shouldbe a minimum of 10 ft. by 3 ft.

Framing a stairwell isn't complicated and isusually defined in the local building code. Ifthe long dimension is parallel to the joists, thetrimmer joists on each side are doubled, asare the headers. Similar framing is required ifthe long dimension is perpendicular to thejoists (drawings, above right). If the headerisn't carried by a partition below, it will have

to be designed for the load.

Making the calculationsCareless measur-ing can get you in a lot of trouble when you're

building stairs. Although the initial figuringmay seem a little theoretical, you'll soon bedoing some fussy finish work based on thesecalculations and the resulting carriages. First,check both the stair opening and the floor be-low for level. If either is out of level, deter-mine how much. You'll have to compensatefor it later. This problem occurs most oftenwith basement slabs.

There are many ways to lay out stairs; thefollowing system teamed with a pocket calcu-

lator works well for me, even though I have toscratch my head to recall what I did last time.Start with the measurement that has alreadybeen determined, the finished floor-to-floor

height. I'll use 108 in. in this case. Then, justfor a starting point to get you close, divide by14, the average number of risers used in resi-

dential stairs. This gives a riser of 7.71 in.,which is a little high. Adding another riserwill reduce this measurement some: 108 in. 15 = 7.20 in. Sounds good. You now know

how many risers you'll be using and how highthey are.

To get the width of the treads (remember,this means the front-to-back measurement ofeach step), use the rise-plus-tread formula inreverse: 17.5 in.-7.2 in. = 10.3 in.

All stairs have one more riser than treads.This is because the floors above and belowact as initial treads, but aren't a part of thestair carriage calculations. You'll have to keep

reminding yourself of this when you lay outthe carriages. I don't know a good way of re-membering this, and I have resorted to draw-ing a sketch of a couple of steps and using itto count the difference. In the example we'reusing, then, there are 14 treads and 15 risers.

The last calculation is the total runthelength of the stairway from the face of the firstriser to the face of the last riser. This is sim-ply the total number of treads multiplied by

this figure you can check to see whether thestairway will fit in the space available. Al-though I now use a calculator for the math,my main tool used to be a stair table like the

thumb is: riser X tread

their width: 14 in. X 10.3 in., or 144.2 in. With


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A Glossary of Stair Terms

BalustersThe posts or othervertical members that hold up the

handrail, usually two per tread.

BalustradeThe complete railing,including newel posts, balusters and ahandrail. Most of these parts areavailable as stock finished itemsat lumberyards.

CarriagesAlso called s t a i r s t r i n g e r s ,s t a i r h o r s e s or s t a i r j a c k s . They are thediagonal members that support thetreads. Carriages can either be f i n i s hs t r i n g e r s or rough stringersfor anoutside stairway, or for an insidestairway hidden from view. R o u g hcarriages, whether they are cut-outc a r r i a g e s or just d a d o e d or c l e a t e d s t a i r s , are made of 2x10 or 2x12

softwood lumber. Finish stringers areusually made of -in. or -in. stock.They either can be cut out (an o p eno r m i t e r e d s t r i n g e r ) or routed (ah o u s e d s t r i n g e r ) .

Closed stairwayStairs with walls

on both sides. In this case a w a l l s t r i n g e r , whether it is a h o u s e d s tr inger or just a s t r ingboard, is nailedto each wall. Closed stairways usehandrails, not a balustrade.

Finished stairwayAny of severalinterior stair types that have risers,treads, stringers and a handrailor balustrade.

HandrailThis rail runs parallel tothe pitch of the stairs. It's held by

balusters or brackets.HeadroomThe vertical distancefrom the lowest point of the ceiling or

soffit directly above the stair to thenos ing l ine , an imaginary diagonalconnecting the top outside corners oftreads. Most codes require at least6 ft. 8 in. for stairs in living areas, and6 ft. 6 in. for basement utility stairs.

Housed stringerThe profile of thetreads, nosing and risers is routedinto a finish stringer. Extra room isleft for wedges to be driven and gluedin between the stringer and the treads

and risers. Rabbeted and groovedrisers and treads are also used.

LandingA platform separating twosets of stairs.

Newel postThe large post at theend of the handrail. There is a s tar t ingn ew el at the base of the stairs, and al a n d i n g n e w e l at turns.

NosingThe rounded front of thetread that projects beyond the face of

the riser 1 in. to in. In the case ofo p e n - t r e a d s t a i r w a y s , it shouldn't

exceed in. In most cases, the

nosing is milled on the tread stock.On open stairways, a half-roundmolding called r e t u r n n o s i n g is nailedto the end of the tread.

Open or mitered stringerThis is acut-out finish stringer used in open

stairways. The treads carry over thestringer, but the vertical cut-outs onthe carriage are mitered with therisers at 45.

Open stairwayThis can be openon one or both sides, requiring abalustrade. In finished stairways, the

open sides will use a mi te r ed oro p e n s t r i n g e r .

RiseThe height of each step from

the surface of one tread to the next.Just as in roof framing, thismeasurement is sometimes called theu n i t r i s e . Many codes call for amaximum rise of in. The height ofthe entire stair, from finished floor tofinished floor, is the t o t a l r i s e .

RiserDescribes the rise of onestep. It is also a stair partthevertical board of each step that is

fastened to the carriages. Risers for ahoused stringer stair are rabbeted at

the top to fit the tread above, andgrooved near the bottom for the treadbelow. Other stairs use 1x square-edged stock. O p e n - t r e a d s t a i r s don'thave risers.

RunAlso called u n i t r u n , this is thehorizontal distance traveled by a

single tread. A 9-in. run is the codeminimum for main stairs. To tal run is

the measured distance from thebeginning of the first tread to the en

of the last treadthe horizontallength of the entire stairway.

StairwellThe framed opening inthe floor that incorporates the stairIts long dimension affects how muchheadroom the stair has.

StringboardDiagonal trim, notused to support the treads, that isnailed to the stair walls. Finishedtreads and risers butt these. Oftencalled s k i r t b o a r d s , b a c k i n g s t r i n g e r s ,

pl a in st r i n g e r s.

TreadIt is both the horizontaldistance from the face of one riser tthe next, and the board nailed to th

carriages that takes the weight of yofoot. Exterior stairs typically use 2xsoftwood treads. Interior stairs use

either -in. hardwood stock milled

with a rabbet and groove to join it tothe risers, or -in. square-edged

stock. Both are usually nosed.

WinderWedge-shaped treads usein place of a landing when space iscramped, and a turn is required in t

stairway. Many building codes statethat treads should be at least the fuwidth of the non-winder treads, 12 iin from their narrow end; or that thenarrow end be no less than 6 in wi

Paul Spring


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Nearly complete, the finish stair at left is missing only its balusters, hand-rail, and molding under the nosing. The newel post is mortised into thefirst tread for stability. This stair uses both an open stringer and treadsand risers that butt-join the skirtboards or stringboards that are nailed tothe wall. Above, kraft paper protects the completed oak treads from con-struction traffic. The open stringer is mitered to the riser, and the treadsoverhang the stringer by the depth of the return nosing with its scotiamolding beneath. The cut-out carriage that actually supports the treads ishidden behind the finish stringer and drywall blocking.

no change will have to be made for the risersto be equal.

A more confusing condition is when thetreads are thicker than the finished floor (C).At this point, I usually draw a four-riser lay-out, at any scale, on graph paper to figure howmuch of a drop I need to make, and if the bot-tom riser needs to be narrower.

How the cut-out carriages are attached oncethey are raised in the stairwell also may re-quire adjustment at the top and bottom of thecarriages (drawings, opposite page, bottomleft. At the bottom, I like to use a 2x4 kick-board nailed to the floor at the front edge ofthe riser (A). If there is a stair opening below,the carriages can be cut to fit around the up-per corner of the framing (B). Stairs take abeating, and should be well secured.

At the top, the header joist usually acts asthe uppermost riser, but sometimes, the floor

will extend a full or partial tread width fromthe framing (drawing A, opposite page, topleft). A 1x4 or 2x4 ledger board can be nailedto the framing (B), and if so, the carriagesmust be notched to fit it. Metal angles orstraps can be used if the carriages aren't ex-posed (C). I like a hanger board because it isquick, neat and strong. I nail the carriages to aline on a piece of plywood, a riser's distancefrom the top. I then raise the whole businessas a unit and nail it in place (D).

Give the carriage a trial fit before sawing itout. I make only the horizontal cut that restson the floor and the vertical cut that leansagainst the framing at the top before trying

the carriage in the stairwell. If you are reallyunsure, use a 1x10 trial board. With the car-

riage in place, you can easily check your lay-out. The treads should be level from front toback, and the carriage should fit on both sidesof the opening. Also make sure that the riserswill all be the same height once the treadsand finish floor are installed.

If everything checks out, what's left is justcutting and fitting. With this basic layout youcan produce the cut-out carriages that areneeded for the stairway shown above, you candado the carriages for let-in treads, or you canjust nail cleats to the layout lines. For cut-outcarriages, use a circular saw as far as you can,and finish them off with a handsaw held verti-cally so as not to overcut the line and weakenthe cut. You can nail the triangular cutouts toa 2x6 for a third stringer if the budget is tight.Use the completed carriage as a pattern to

trace onto the other 2x12, and then cut thepencil line to get an exact duplicate.

Treads and risersOn a closed stairway,the cut-out carriages sit inside the finish wallstringers, which are called skirtboards, orstrings. These are usually 1x10, and should benailed hard against the wall so that the snugfit of previously installed risers and treadsisn't spoiled by the skirtboards spreadingwhen newly scribed boards are tapped intoplace. They should be installed parallel to thenosing line, and as high as possible withoutexposing any wall where the riser and treadmeet. Don't nail the cut-out carriages to the

skirtboards on a closed stairway, or the mi-tered stringer to the outside carriage on an

open stair. Instead, hold the carriages about3 in. away from the walls, so that they are

bearing only at their tops and bottoms. Thiskeeps the treads and risers from splitting as aresult of nailing too close to their ends. Skirt-boards and risers can be made of pine to easethe budget, but the best treads are oak. Thestandard thicknesses for treads are in. and

in.1 like to rip all of my treads and risers to

width before beginning the assembly. Keepthe risers a hair narrower than what's calledfor. Crosscut both risers and treads to 1 in.longer than the inside dimension between the

skirt boards. This allows them to fit at a lowenough angle to get a good scribe and stillhave a little extra to cut off. If the stair is openon one side, the treads will have to be rough-

cut long enough to leave a -in. scribingallowance on the closed side, and some over-hang on the open side, which gets a returnnosing. The risers will need at least a 45miter to mate with the open stringer. Use a

radial arm saw or handsaw for this.Stair assembly usually begins at the bottom.

The first two risers are fit and nailed, andthen the first tread is pushed tightly againstthe bottom edge of the riser for scribing. Forthe stair pictured above, I first had to cut theopen, or mitered, stringer. It was pine, andwas laid out like the carriages with the excep-tion of the vertical cuts, which extend beyondby the thickness of the riser material to form


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Stepladderstairway

A cleated or dadoed stairway atan angle of from 50 to 75 isconsidered a stepladder stairway,or ships's stairway. The rise onthese ladders can be from 9 in. to12 in. As the angle of thecarriages increases, the rise

increases. A 50 angle should

have about a 9-in. rise. A 75

angle should have about a12-in. rise.

As with all other stairs, therelationship between the heightof the riser and the width of thetread is important. But in thiscase, their relationship isreversed. The tread width onstepladder stairs will always beless than the riser height.

If you know what riser heightyou'll be using, the easy formulafor calculating the tread width isthis: tread width = 20 - 4/3 riserheight. If you use a 12-in. rise,then the tread will be 4 in. You

can also rearrange this formula tosolve for riser height (riser height= 15 - 3/4 tread width) if youknow what tread width you want.This is useful if you are limited inhow far out into a room the baseof the stair can come.

A simple way to lay out a

stepladder stairway is to lean a2x6 or 2x8 carriage at about 75in the stair opening. Lay a 2x4 onedge on the floor, and scribe apencil line across its top edge totransfer a level line from the flooronto the carriage. Mark thevertical cut, at the top, in a

similar manner.Make these cuts and set the

carriage back in place. Measurethe floor-to-floor height anddivide by 12 in. to get the numberof risers. You'll end up with awhole number and a fraction. Forinstance, if your total rise is106 in., the number of risers willbe 8.83. That's close enough tocall it 9 risers. Divide this backinto the total rise of 106 in. to getan accurate riser dimension of11.77 in., or about in.

The easiest way to lay out thecarriages is to make a story pole

using dividers set at aboutin. to step off nine equal

segments within the 106 in. Itmight take a few tries adjustingthe dividers to get it to come out

just right. You can even find theriser dimension without the mathby making a few divider runs upand down the story pole.

With the carriage in place,mark each tread from the storypole. A level line at each marklocates the treads. A bevel squareset at the correct angle will alsowork. The treads can be cleatedor let in with a dado. B.S.

an outside miter. I'm most comfortable maing these cuts with a handsaw. Keeping thangle slightly steeper than 45 allows tfaces to meet in an unbroken line, without ainterference at the back of the joint. Tmiters were predrilled, glued and nailed w8d finish nails (photo previous page, right)

The treads are initially cut to overhang topen stringer, by the same dimension as tnosing. Then a cross-grain section is cut o

so that a mitered corner is left at the ouedge. This accommodates a return nosingalso like to put a piece of nosing at the rear the tread where it overhangs, although y

can just round off the back end of the retunosing. If the mitered stringer doesn't snug uperfectly under each tread, don't worry. Tcrack will be covered by the cove or sco

molding that runs under the nosing. It's moimportant to get good bearing for the tread the cut-out carriage, and a little shimming block-planing will help here.

Once beyond the open side of the stair, ywill be fitting treads and risers on a closestairway, scribing to the skirtboard on easide. With a 1-in. allowance for scribing, s

the scribers at in. for the first side. Set ttread or riser with the side you are going scribe down in place on the carriage anagainst the skirtboard. The other end will ridhigh on the other skirt. If you are working a tread, make sure it is snug to the riser aloits entire length. Risers should sit firmly othe carriages to get an accurate scribe. I usehandsaw to back-bevel the cut on risers, bu

keep the cut square at the front of the treawhere the nosing protrudes, and then anglethe rest of the way. If necessary, use a bloplane to make sure the cut fits.

Next, get the inside dimension at the baof the tread or lower edge of the riser, dpending on which you are fitting. A wood r

er with a brass slide works well here. Transfthis dimension to the board you're workion, set the scriber to the remaining stock, anmark the board. Cut the boards the same w

you did the first time. Cut carefully, remebering that you can always plane it off, b

you can't stretch it. However, don't make tcut too strong either. Trust your measure.

Careful cutting and fitting are importawith this kind of stair, and a little glue, ansome nails and wedges in the right place wowonders as time goes on. Risers and treaare nailed to the carriages with 8d finish na

through predrilled holes. A sharpened dheaded 8d finish nail chucked tightly into electric drill makes a snug hole every time

Stairs that aren't made from rabbeted sto(like housed-stringer stairs) can be kept tgether if you drive three or four 6d commnails through the bottom of the riser into tback of the tread. This should be done as yofit your way up the stair. Two 1x1 blocks, 2 long, glued behind each step at the intersetion of the upper edge of the riser and tfront of the tread will cut down a lot on movment too. Any gaps between the carriage antreads should be shimmed from behind wi

wood wedges to eliminate squeaks.

Stairs Designin and Building

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