64 FINE HOMEBUILDING

Framing Curved WallsUse a tape measure as a compass and thick plywood for the wall plates

BY RYAN HAWKS

JUNE/JULY 2002 65Drawings: Dan Thornton

iece of cake,” I replied the first timesomeone asked whether I couldbuild curved walls. But as I looked

over the plans, I didn’t have a clue how toturn that drawing of a round room into real-ity. Late in the day, after the generators weresilenced and the crews were on their wayhome or to the bar, I prowled around at acouple of jobs being built by one of the bestframing contractors in San Diego.

By looking at his work, copying his notesfrom the floor, asking questions the next dayand applying ingenuity, I built my first radiuswall as if I’d done it a hundred times. Thatwas a few years ago; I’ve since developed amore refined technique that I use now.

A chalkline represents the base ofthe radiusThe job shown here is a 180° radius wall, ora half-circle, that extends from two parallelsidewalls (photo facing page). This radiuswall is the simplest type (sidebar p. 67).

To lay out the radius, you first must estab-lish the baseline. In this case, the baseline con-nects the ends of the two sidewalls. I snap achalkline on the floor to represent the base-line, then mark its center (half the length ofthe baseline is the outer radius).

A nail partially driven into the floor at thiscenter mark becomes the pivot point for mytape measure, which I use as a compass tomark the inside radius of the wall plate on thefloor (top photo). Most tapes have a slot cut inthe hook at the end for just this purpose: Theedge of the nail head rides in the slot as youhold a pencil to the edge of the tape at theproper point and mark the radius to the floor(bottom photo).

Complications arise when somethingstraight, such as a door or a window, goes intoa curved wall. On this job, the architect hadcalled for the wall to be 51⁄2 in. thick and forthe door to be 3 ft. wide. If I’d built it asdrawn, the center of the door-jamb headwould have intruded past the wall surface.After consulting the architect, we thickenedthe wall to 71⁄2 in. and downsized the door to2 ft. 8 in. (drawing right)

Thick plywood makes up the radius-wall platesI usually make radius plates from two top andtwo bottom layers of 11⁄8-in. plywood, whichadds up to the same 41⁄2-in. thickness as three2x plates, avoiding the need to custom-cutstuds. When framing on a slab, however, as

here, the bottom plate must be treated ply-wood, which is available in a maximumthickness of only 3⁄4 in. Cutting six 3⁄4-in. platesto achieve a 41⁄2-in. plate thickness would havebeen a lot of work. Instead, I used two 3⁄4-in.bottom plates and two 11⁄8-in. top plates; I cus-tom-cut the few studs that this wall required.

This particular radius was smaller than 48 in., so marking the plate radii on the ply-wood was straightforward. I simply set a nailin a line bisecting the sheet and used my tapeas a compass to lay out the inside and outside

radii on the plywood (photo top left, p. 66).(See sidebar p. 67 for walls whose radius isgreater than 4 ft.)

If a radius is greater than 10 ft., I can cut theplywood plates with a 71⁄4-in. circular saw, butI cut these tight-radius plates more conven-tionally using a jigsaw. After cutting the firstplate, I used it as a template to mark the oth-er plates as well as the rough sills and the nail-ers at the top of window and door openings.

Once the plates are cut, I place the treatedbottom plate on top of the anchor bolts, lin-

“P DRAW THE RADIUS ON THE FLOORLayout begins with a baseline and a centered nail (top photo). A chalkline be-tween straight walls from which the curved wall will spring forms the baseline.A nail centered in this line is the centerpoint of the curve. The slot on the hookof the tape fits around the head of the nail, allowing the tape to be used as acompass (bottom photo), in this case to lay out the inside radius of the wall.

2x6 wall thickness

2x8 wall thickness

Centerpoint

Footprint of 2-ft. 8-in. doorjamb

Footprintof 3-ft.door jamb

Fitting doors and windows

On this radius, the specified3-ft. door’s jamb would have

protruded past the inner-wall finish.The fix was to change 2x6 studs to

2x8s and the door to 2 ft. 8 in.

ing up one end with the intersecting straightwall. I use my square to align the plate withthe radius I marked on the concrete and thenhammer the plate over the anchor bolts toleave indentations (photo bottom left). Theseindentations are where I drill for the bolts.

With the bottom plate drilled, I lay it backdown on the anchor bolts to check the fit andto mark the ends to be cut where it meets thenext section of plate (photo bottom right).One end meets the straight wall, and its cut-line matches the baseline of the radius. If theother end is in the middle of the wall, I wantthis cut to fall in the center of a stud. I findthis point by wrapping my tape around theoutside of the plate and then marking thecenter of the stud that falls closest to the endof the plywood.

With the first plate section cut and in place,I repeat my actions to cut and drill remainingsections. Once the plate is in place, I detail thedoor and window openings on the plates(drawing facing page).

The first step in laying out the windowopenings is to find their centers by measuringalong the outside of the plate. With therough-opening centers marked, I snap chalk-lines between them and the centerpoint.Aligning my framing square on the chalkline,I use the square to mark the rough openingon the outside and the inside of the plate, thento connect the marks I’ve made (top photo,facing page). These layout lines aren’t radi-al; rather, they’re parallel to the center-of-opening radius. If they were radial, the roughopening would be narrower on the insidethan on the outside.

Kings and trimmers are custom-cutBecause they are parallel to the centerline oftheir rough openings (as opposed to being radial), the king studs and trimmer studs arewider than the other studs, and their edgesmust be beveled to fit neatly on the plates.The bigger the rough opening, the bigger thebevel angle.

I find the rip angle and depth of the kingand trimmer studs by laying a block on theplate where the king or trimmer stud sits andscribing. On this job, with its 2x8 studs, I wasable to rip the kings and trimmers from 2x10stock (top photos, p. 68).

After marking the rough openings, I lay outthe stud locations on the outside of the plate(photos bottom left, p. 68). Most architectsnote the stud spacing on the plans. Usually,the tighter the radius, the closer the stud spac-ing to provide backing for the wall finishes.On this job, the studs were on 8-in. centers.

It’s possible to mark the studs exactly radialon the plates by pulling a chalkline from thecenterpoint to every layout mark. I usuallydon’t bother with this step, however, findingthat I can visually check the stud alignmentwell enough.

The headers are standard, straight lumberthat sandwiches between two pieces of 11⁄8-in.plywood, extra pieces I cut along with theplates (photo bottom right, p. 68). I size this

66 FINE HOMEBUILDING

FIT THE BOTTOM PLATEThe plates are marked to be cut using a tape as a compass(photo left). Using a square to ensure that the plate aligns withthe layout line, the author taps the plate over the anchor boltsto mark the hole locations (photo below left). With the first sec-tion of plate drilled and placed, a square again is used to align asecond section, and the author marks it for length (photo below).

JUNE/JULY 2002 67

MARK THE ROUGH OPENINGThe author snaps a radius line to the center of the rough opening, thentransfers that line to the bottom plate (photo below). The centerline istransferred from the bottom plate to the top (photo bottom left), wherethe locations of the kings and trimmers are marked (photo bottom right).

A

A,C = RadiusB,C = RiseD,E = Run

Arc DE lessthan 1800

B C

E

Radius-wallvariations

Centerpoint

RadiusCenter ofroughopeningRegular studs

are radial.

King andtrimmer studsare ripped fromwider stock.

Bevels approximate plate.

King and trimmerstuds are parallelto center-of-opening radius.

Large-radius wall platesWhen the radius is larger than 4 ft., thecenterpoint can’t be on the plywood. Tofind the centerpoint, snap a chalklinethat’s at least the length of the radiuson the floor. Next, bisect the plywoodwith a chalkline, then align theplywood’s chalkline with that on thefloor. Locate the centerpoint of theradius along the chalkline, and use atape measure to swing the radius.

Chalkline bisects plywood.

Centerpoint

Chalklines align.

When the arc is less than 180˚Jack radius walls, where the arc of thewall is less than 180˚, are common, butfinding the radius of these walls so thatyou can lay them out is not so obvious.Jack radius walls are usually specifiedwith two factors: rise and run. As anexample, say the run is 8 and the rise 2.Plug these two numbers into a simplealgebraic equation to get the radius(drawing below).

Radius = (Run2 + 4Rise2) ÷ 8Rise

Radius = (82 + 4 x 22) ÷ (8 x 2)

Radius = 5

D

Laying outdoors and windowsThe layout of the regular studs isradial, but the layout of the kingand trimmer studs isn’t. They must beparallel to a radius that goes to the center ofthe rough opening; otherwise, the opening wouldtaper and the window or door wouldn’t fit. Kingsand trimmers must be cut from wider stock.

68 FINE HOMEBUILDING

GETTING THE KINGSAND TRIMMERS RIGHTThe simplest way to find the widthand bevel of kings and trimmers is toscribe a scrap block in place (photo below) and use it to set up atable saw to rip the kings and trim-mers from wider stock (photo right).

PUTTING STUDS AND NAILERS IN THEIR PLACESStuds on curved walls are often spaced closer than 16 in. o. c., in this case 8 in.Laying out the outside edge of the plate ensures that the sheathing joints,though not the drywall, land on studs (photo left). Snapping radial chalklines foreach stud would ensure perfect alignment, but lining up the studs by eye worksfine and is a lot faster (photo below left). The headers are standard. Only thenailers for the wall finish (extra plate stock) are curved. Assembling the headerswith a square as a guide ensures their fit (photo below).

JUNE/JULY 2002 69

STUDDING OUTCurved walls want to roll, so filling in thestuds takes two carpenters. The authorstarts with the kings and trimmers (photoabove). Next come the regular studs (photobelow) and the midwall blocking, which hescribes from the laid-out plates (photo left).

plywood by laying it on the detailed plates andmarking it to fit between the king studs.

Nail the wall together where there’sroom to maneuverI like to frame these walls on a nice flat floor,but I framed this one outside because the jobwas a remodel with no room inside for me toframe a curved wall. Working with curvedcomponents is cumbersome, and it helps tohave one person holding the wood and anoth-er one nailing.

I begin by nailing the headers to the kingstuds and trimmers, and then to the plates (pho-to top left). Next come the studs, and after nail-ing in more than half of them, I chock the wallwith a couple of scrap blocks to prevent it fromrolling. The rest of the wall is filled in one studat a time by two carpenters, one who is holdingthe studs and another who is doing the nailing(bottom photo).

Round walls are usually heavier than straightwalls, and they like to roll. I always take extraprecautions when standing a round wall; hav-ing too many carpenters raise a wall is betterthan not having enough. When possible, I raiseradius walls from the position of having theends of the plates, as opposed to their centers,on the floor. This approach prevents the wallfrom rolling as it’s being raised.

Because of the existing house, that approachwasn’t possible on this job. There’s really notrick here: Just have more muscle than wall onhand. Because the plates differ in thicknessfrom straight wall plates, they don’t lap to tiethe walls together. They’re simply butted,plumbed and tied together with metal strapswrapped around both intersecting plates (pho-to above right).

Sheathing the wall is simple. I use 3⁄8-in. CDXplywood because it’s flexible, and I sheathe asI would any other wall. �

Ryan Hawks is a carpenter in Pacific Beach,CA. Photos by Tom O’Brien.

Lack of plate overlap

means metal strapsmust tie curvedwall to straight.

And yes, it wouldbe safer to per-

form this operationon a ladder.