Chapter 8. DOOR AND WINDOW FRAMES

chapter 8. DOOR AND WINDOW FRAMES8.1 GENERAL8.1.1 FramesThere are two basic types of door andwindow frames: the traditional system ofinterlocking wood members and theintegral-flange metal sections. Variations ofthe latter include metal clad and plasticcoated, but they are similar in sections anddimensions and equal in performance. Also,among the metal types are those designedto be installed in wood-frame buildings andthose designed for concrete openings.We will not deal with those frames that aredesigned for concrete-type openings, exceptto mention that they are not intended (wehope) to be installed in wood-framebuildings. To use this type of section inwood-frame buildings is to invite disaster.If such installations are required, thedesigner must pay very close attention tothe detailing.8.1.2 Door SillsIn general, door openings should behandled in the same way at the head andjambs as are windows. Sills requiresomewhat different treatment. The sillportion of wood-frame door assemblies issusceptible to water penetration and mustbe correctly detailed. Sometimes door sillsare made from decay-resistant wood ormetal, and are not susceptable to decay.However, water penetration under the silland in the surrounding framing members isparticularly troublesome.8.1.3 Installation of Membrane AroundDoor SillsSpecial attention should be paid to thejamb-sill corner at the door sill. This edgecondition, when not properly detailed, willallow water penetration to the wall interior.(Figures 8-1A to 8-1G) illustrate the properinstallation of felt membrane around a doorsill in a step-by-step manner.8.2 WOOD FRAMESTo make a watertight frame head condition,two facts should always be remembered:water wants to run down hill, and windwill push it horizontally or up vertically. Ifthe designer keeps these facts in mind andmakes provision for them, particulary atcorners or intersections, the openingprobably will perform well. Other importantconsiderations are the following:8.2.1 General1.For general membrane sequence, seemembrane installation under generaldetailing (Chapter 3).2.The jambs are between the head andsill, not the other way around.

WOOD: DETAILING FOR PERFORMANCEbJamb framingSubfloorDOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8-1A

WOOD: DETAILING FOR PERFORMANCEDOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8-1Bchapter 8 - 3

chapter 8 - 4WOOD: DETAILING FOR PERFORMANCEFelt split sheetapplied verticallyaround frame-----'I ','I-Feltsplit sheetor plastic flashing(preferable)\\\\'\DOOR SILL DETAILASSEMBLY A T JAMB-SILL CORNERFigure 8-1C

WOOD: DETAILING FOR PERFORMANCEchaoter 8Felt left Ion f o rcIarnpin1 beqweentrim & oorIIIII 'I I ',''I II I',DOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8 - 1 DFelt split sheetapplied verticallyFelt split sheetor preferablyplastic flashrng-5

chapter 8 - 6WOOD: DETAILING FOR PERFORMANCEDOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8-1E

WOOD: DETAILING FOR PERFORMANCEDOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8-1Fchapter 8 - 7

chapter 8 - 8WOOD: DETAILING FOR PERFORMANCE-Sillwith slopedsurfaceDOOR SILL DETAILASSEMBLY AT JAMB-SILL CORNERFigure 8 - 1 G

WOOD: DETAILING FOR PERFORMANCE3. The trim holds the frame in place. Theshims and frame nailing should onlyfunction only to align and temporarilyplace the frame.4. Allowance must be made for someshrinkage and swelling of members.5. Allowance must be made for adequatetrim overlay on the frame to receivegood nailing. In severe locations,sealant may be advisable'for the joints.chapter 8 - 93.8.2.1.3 Sill1.Portions of the sill exposed to theweather should slope at least 12degrees from horizontal.2.Ends of the sill should project beyondthe opening over siding at least slightlymore than the width of the jamb trim.3.Ensure that the sill sets tight to themembrane.8.2.1.1 Head1. Carry the jamb membrane up andunder head trim and membrane.2. Install metal flashing under headmembrane and over head trim. Extendflashing over edge of trim and turndown one inch.3.4.A gap between the metal flashing andthe siding is desirable to avoid wettingand possible staining of the siding. Donot seal this joint.See &tail, for typical condition (Figure8-2).8.2.1.2 Jamb1.Turn the split sheet around the frameopening. Lap it over the sill sheet. Thedesign should encourage exterior waterdrainage, if a leak develops.2. The membrane sheet should be carriedout and clamped between the jamb trimand the frame. This joint must be tightto avoid wind-induced water infiltration. Remember to carry this membraneup and under the ends of the headtrim.Jamb trim should be tight to siding. Insevere exposure locations, with shiplapor other uneven surface siding, sealantsor gaskets can fill voids.8.2.2 Wood Window in Plywood PanelSiding (Figures 8-2 to 8-4)The dimensions of the head flashing legsdepend on the use condition, but should beat least the "A" dimension. A 318 inch gapmust be provided between the flashing andthe plywood panel to avoid excessivewetting of the plywood by capillary action,as water will collect at this flashing edge.The jamb detail shown in Figure 8-3 willprotect the window opening from waterseepage from the side. In some cases, itmay be necessary to terminate the plywoodpanel at the jamb over the center of a stud,so the adjoining plywood panel above andbelow the window can be nailed into thesame stud. In these cases, the jamb trimshould be wide enough to cover over thejoint in the panel siding.

chapter 8-10WOOD: DETAILING FOR PERFORMANCEEXTERIORExterior head t r i mNote: For "A" dimensionsee Table 3- 1WOOD WINDOW DETAILHEAD DETAIL I N PLYWOOD SIDINGFigure 8-2

WOOD: DETAILING FOR PERFORMANCEchapter 8EXTERIORWOOD WINDOW DETAILJAMB DETAIL IN PLYWOOD SIDINGFigure 8-3-11

chapter 8-12WOOD: DETAILING FOR PERFORMANCEEXTERIORWOOD WINDOW DETAILSILL DETAIL IN PLYWOOD SIDINGFigure 8-4

chapter 8 - 13WOOD: DETAILING FOR PERFORMANCEWood window sills should cover panelsiding at least 314 inch to protect thewindow opening from rain, as shown inFigure 8-4. If a manufactured sill is usedand does not provide a 314 inch overlap,flashing should be added at this joint. Inwind-driven rain locations, it will be necessary to provide metal flashing because the314 inch lap is simply inadequate. In special cases, a trim member can be adequate,if the wall membrane is well detailed.impossible to give general guidelines thatwill govern all conditions. However, havingsaid that, now let us try. At the risk ofbeing repetitious; water wants to run downhill and that wind will push it bothhorizontally and vertically. Pay attentionand make provisions for this, particularly atcorners and intersections.1.When possible, use units with weldedcomers that have a continuous,unbroken nailing flange. These unitsprovide an easier task of keeping thewater out of the building framing.Simply follow the guidelines set forthin membrane installation in Chapter 3.2.When welded comers are not feasible,such as in sliding door units and otherknockdown assemblies, other stepsmust be taken:8.2.3 Elements of a Good Wood DoorSill DetailThe wood door sill should be made fromnaturally decay-resistant wood or should bechemically treated. Adequate sill sectionscan be milled from clear vertical grainstock (see Figure 8-5 for a good samplesection). The sill should be cut so that itcovers the exterior siding material by atleast 314 inch. If the sill does not providesuch coverage, or if the sill is exposed tosevere environmental conditions, metalflashing should be used to protect the jointfrom wind-driven rain. The underside of thesill should be sloped downward at least 12degrees; otherwise a drip cut should beprovided. To be effective, a drip cut mustbe at least 114 inch wide by 114 inch deep.To further protect against wind-driven rain,the felt membrane behind the siding material should continue to run under the doorsill as illustrated. Figure 8-6 illustrates apoorly designed wood door sill section.8.3 METAL FRAMES8.3.1 GeneralBecause of the wide detail variation inmetal doors and windows, it is almostOn the backside of the frame, applylarge, heavy globs of sealantcontinuously along all metal-to-metaljoints. This sealant must be appliedto clean metal and must lap surfacesat least 318 inch to obtain goodadherence to both legs. Sealant mustalso have enough body to withstandthe racking of the frame duringinstallation, plus future movement.Sealant can also be used whennailing flanges are mitered.When nailing flanges are notched(as in most door cases), a metalcomer piece set in sealant is themost foolproof. However, pressuresensitive waterproof tape can alsodo a good job. Again, allow lots ofoverlap of tape to metal.

chapter 8 - 14WOOD: DETAILING FOR PERFORMANCESill made .from naturallydecay r e s s t a n twood orpressure treatedWOOD DOOR SILLRECOMMENDED SECTIONFigure 8-5

WOOD: DETAILING FOR PERFORMANCEchapter 8F e l t m e m b r a n e notc o n t n u e du n d e r s l lWOOD DOOR SILLPOOR PRACTICEFigure 8-6-15

chapter 8-16Sliding door sills often do not comewith nailing flanges. When thisoccurs, metal flashing should be used,and it must be integrated with thejamb condition. Fastenings must beproperly sealed.8.3.2WindowsFigure 8-7 illustrates the desirablecharacteristics of a good metal windowwith nailing flanges. The length of theflange should be "A" dimension (see Table3-1 in Chapter 3). The horizontal ledgesshould be sloped a minimum of 12 degrees.Weep slots and drip edges are alsodesirable to remove collected water.8.3.2.1Metal Window in Plywood PanelSiding (Figures 8-8 to 8-10)If trim is desired in a plywood panelsystem, it should be of a solid lumberstock (i.e., not plywood) and should besloped on top at least 12 degrees. In addition, sealant should be provided at the topof the trim to keep moisture away from theinner surface in between the siding and thetrim; this area is vulnerable to decay. Silltrim should also be sloped on the top surface and sealant applied to this area toprotect against wind-driven rain that pushesmoisture over the edge of the panel andwets the backside.8.3.2.2' Metal Window in Lumber Siding(Figures 8-11 to 8-13)In a lumber siding system, flashing shouldbe provided over the head trim. Optimally,WOOD: DETAILING FOR PERFORMANCEthe top of the head trim should be slopedand should extend to the outer edge of thejamb trim. Lumber siding should be buttedagainst the head while it is covered by thejamb trim. This avoids an open jointbetween the jamb trim and the siding,where the membrane will be exposed. Asusual, drip cuts should be provided whereneeded, and all horizontal ledges should besloped to aid drainage.8.3.3Elements of a Good Metal DoorSill DetailExtruded aluminum sills are goodalternatives for wood sills because they areunaffected by moisture. From the manycommercially available sections, sillsections with a longer "leg" on the exteriorside are preferable. This leg covers theupper edge of the exterior siding materialand protects this joint from wind-drivenrain (see Figure 8-14). If a sill without aleg is used, or if the leg covers less than314 inch of the exterior material, flashingshould be provided (see Figure 8-15).Figure 8-16 illustrates a poorly designedmetal door sill detail.Metal sills are usually fastened to thesubfloor by long screws. The screwpenetration holes are vulnerable pointsbecause they are not watertight. The feltmembrane should be continuous under thesill and extend beyond the screw holes.

chapter 8WOOD: DETAILING FOR PERFORMANCE-17Head framing fin1 " absolute min., 1 -1/2"1IpreferredSlope is highly desirable-PSection should be flush attop.-idHEAD SECTIONnOutside section should slideU-tI/-I -/-I-of rear sill leg important/ Heightfor water resistance to winddriven rain. Higher leg equaisbetter performance.JWeep slot should drcin toouter face and lead to dripedge.Lip should be 3/4" to rotecttop edge of siding ma erialP(ISill framing finSILL SECTIONMETAL WINDOW DETAILDESIRABLE PROPERTIES OF AHORIZONTAL SLIDING WINDOWFigure 8-7