b'After the opening is prepared for the replacement Upper Windowwindows, remove all sashes of the windows to bemulled.Note: Leave strap (if provided) on all win-dows until fully installed.Measure the opening height approximately whereunits are to be mulled.Cut H mullion 1/4 less Snap-inthan opening height. Then measure opening widthMullat top and cut continuous head expander 1/8 less Snap-in Mullthan the measured width. Also measure openingwidth at bottom and cut continuous sill angle 1/8less than that width. Lower WindowStarting at the top of the replacement windows, slidetheH mullion onto windows side by side.Liquid How to Join with "U" Mullssoap on inside of mullion can make this easier.Install the continuous head expander over top of It is possible to join and stack multiple windows the windows and H mullion. to accommodate various architectural, design, and structural situations. When stacking windows,or where you want the windows joined prior to Head Expander installation, snap-in "U" Mulls work better than "H" mulls because they are structurally joined toboth sides of the windows. Common to welded (fusion corner joints) vinyl win-dows and especially in awning and casement types,the frame - inside and outside on all perimeters -contains a groove that will accept a specially extruded "U" shaped mull that snaps in to "lock" the units together. If the windows you are installinghave this groove, then it is preferable to use the "U"mull. It is important to note, however, that the weightof vinyl replacement windows with 3/4" insulatedglass can be excessive and the mulls may not bestrong enough to hold the weight if a multiple unit isto be lifted into an opening already mulled. The ruleof two people per window also applies to multiple"H" Mullion units. Therefore, be sure you have enough help whenSill Support lifting mulled units into place.When stacking windows or mulling more than twounits together, in most instances, it is easier andInstall full-length sill support if necessary and set more efficient to mull the units prior to installation.windows into openings.Shimming the sides and However, when the combination unit will be unwieldyaligning the windows carefully, try to keep theor extremely heavy, partial mulling can be doneunits tight to the H mullion for maximum support. before installation, and the remaining units attachedOnce mounted, check plumb and square. Thenafter they are placed in the opening.re-install and align all the sashes. Complete the The available, U-shaped,snap mulls are applied oninstallation with caulk, capping and trim asthe inside and theoutside of the multiple windownecessary.Now you can remove any provided straps. units.Place the two windows together and press theTo mull vertically (stacked units), remove anylegs of the mull down into the slots in the windowoperating sash.Using the H mullion, cut it 1/8 frame.As shown in the diagram, the tabs on theless than opening width. Place the head expander if mull legs snap into the slots holding the two windowsprovided) on the top window, and mount the sill firmly together.It is important that the mulls beangle (if necessary) below the lower window. accurately pre-trimmed to the proper length prior touse because they are difficult to remove.Since theCarefully install mulled unit into opening.Re-install mulls protrude from the face of the window frame,and align any removed sash. As before, remove any they should be trimmed to allow for any moulding orprovided straps, and complete the installation with trim to be applied after installation.This will providecaulk, capping, and trim as necessary. a neater, more easily weather-sealed job. Window Fitters Guide to Window Installation782020 AWDI, LLC Do not reproduce without permission'