Essential Series Windows

Mulling Instructions for Field Application

Revised on 2019-07-29

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Before You Begin

Mull Kit Parts

  • 1 - Mull pin
  • 2 - Mull bracket
  • 2 - Mull plugs
  • 4 - Rivets
  • 1 - Sill mull bracket (for Sliding Window products)
  • 2 - Flat sill structural brackets
  • 4 - 90-degree bent structural brackets with 8-#7 x 5/16" screws
  • 2 - Mull covers (interior and exterior)
  • 2 - Nailing fin connector gaskets

Inspect the mull kit to ensure that there are no damaged or missing parts. Parts listed above are included in each kit. More than one kit may be needed depending on configuration.

Tools and Supplies Needed

  • Rubber mallet
  • Rivet gun
  • Caulking gun
  • Hacksaw
  • Silicone sealant
  • Screw gun/drill with 7/32" drill bit
  • Screwdriver with a #2 Phillips head bit

Caution!

Always wear the proper eye and ear protection when using power tools. Follow all manufacturers’ instructions for application and clean up of sealants.

NOTE: Numbers listed in parentheses () are metric equivalents to the nearest whole number.

Warning!

Drilling, sawing, sanding or machining wood products can expose you to wood dust, a substance known to the State of California to cause cancer. Avoid inhaling wood dust or use a dust mask or other safeguards for personal protection. For more information go towww.P65Warnings.ca.gov/wood.

Preparing the Windows for Mulling

1. Remove and properly discard all shipping material.

2. Inspect the unit to make sure it is the right size, color, etc. and that there is no damage. If you find something wrong with your windows, contact your local Marvin representative and provide them with customer service number located in one of the corners of the glass. See Figure 1.

Figure 1

3. Remove and set aside all screens and loose hardware.

4. Lay the units to be mulled on a flat sturdy surface exterior side up. Remove all nailing fin, if present, from windows at the mull and perpendicular to the mull. See Figure 2.

Figure 2

5. For J-Channel applications: At the corners of the mullion, carefully remove the outer wall of the accessory kerf with a hacksaw. See Figure 3. (This operation does not need to be done at the sill corners of sliding window products.)

Figure 3
1 Notch Corner

Mulling the Windows

1. Set the units to be mulled close together and slide the mull pin down the nailing fin channel on both units. If necessary pound the pin in with a rubber mallet or plastic hammer. See Figure 4.

Figure 4
1 Mull pin

2. Insert the mull plugs with the injection hole oriented toward the exterior. See Figure 5.

Figure 5
1 Mull plug

3. Loosen the screws from the interior corners of the windows on both ends of the mull. See Figure 6. (Remove screws from sill completely for sliding window products.)

Figure 6
1 Loosen interior screws

4. Place the brackets as shown. Fasten using screws loosened in previous steps. See Figure 7. Use the smaller bracket for sill mullion joints on sliding window products. See Figure 8.

Figure 7

Figure 8
1 Sill mull bracket

5. Drill out first layer of Ultrex using holes in end of bracket as a guide. Use the 7/32" drill bit to drill out the rivet holes. Fasten all rivets. See Figure 9. (Sill mull brackets on sliding window products do not require rivets.)

Figure 9

6. Install the exterior mull cover. These should be flush with the interior edge of the accessory kerf to allow for J-channel application. You may have to seat the cover with a rubber mallet or wood block and hammer. Flip the assembly over and install the interior mull cover in the same manner. See Figure 10.

Figure 10

NOTE: Take care when handling or flipping the assembly.

NOTE: Take care when handling or flipping the assembly.

Sealing the Assembly

NOTE: Be sure the sealant used is compatible with any flashing materials used to install the window into the rough opening.

1. Using a high quality sealant loaded into a caulking gun, insert the nozzle into the injection hole on the mull plug and inject with sealant. You will know there is enough sealant injection when overflow appears in the nailing fin channel below the injection hole. See Figure 11.

Figure 11
1 Squeeze out

2. Replace the nailing fin on the frame perpendicular to the mull. Leave sill nail fin off at this point. Slide the nailing fin in from the corners all the way until they butt up against each other over the mull plugs. Install the nail fin connector gaskets and seal around the edges of the connector. See Figure 12.

Figure 12

3. At jamb and head jamb mullion joints, install 90-degree bent structural brackets on both sides of the mull within 6" (152) on both ends. DO NOT apply 90-degree bent brackets to sill. Follow the instructions sent with the brackets. See Figure 13.

Figure 13

4. For sill mullion joints, take previously removed sill nail fin and cut sill nail fin at each mullion joint location and shorten the ends of each by 3" - 3.5" (76-89) near each mullion to allow space for the flat sill structural brackets and nail fin pieces into the sill T-slot. See Figure 14.

Figure 14
1 Sill structural bracket (flat)
2 Sill structural bracket
3 Nailing fin

NOTE: Be sure the sealant used is compatible with any flashing materials used to install the window into the rough opening.

2W x 2H Configurations

NOTE: When mulling All Ultrex windows in 2W X 2H configuration, you will need three mull kits.

Double Hung and Single Hung Operators cannot be mulled above other units.

1. Using the techniques outlined in the previous steps, prep, mull, and seal the two vertical sections first (horizontal mulls). Do not apply nailing fin until the entire assembly is complete. See Figure 15.

Figure 15

2. Mull and seal the two vertical sections. See Figure 16.

Figure 16

3. Apply nailing fin, nailing fin gasket connectors and structural brackets on the entire assembly. See Figure 17.

Figure 17

NOTE: When mulling All Ultrex windows in 2W X 2H configuration, you will need three mull kits.

Double Hung and Single Hung Operators cannot be mulled above other units.