How to Use Joint Compound on Exterior Jobs

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Things You'll Need

  • Bucket

  • 4-inch mud knife

  • 6-inch mud knife

  • 8-inch mud knife

  • Joint tape

  • 80 grit sandpaper

  • Exterior latex paint

  • Paint roller

  • Paint tray

Tip

Never mix or apply exterior joint compound when temperatures drop below 50 degrees Fahrenheit.

Warning

Remove and discard any dried pieces in the mix.

Mix and apply setting type joint compound to exterior drywall.
Image Credit: Jupiterimages/Photos.com/Getty Images

Setting-type joint compound is ideal for exterior construction. Exterior jobs need a durable joint compound. Setting-type joint compound dries hard, resists moisture and requires just a few coats to get the job done. Outdoor joint compound application is similar to indoor applications. But watch out for the weather. Avoid applying joint compound on humid, rainy days or when temperatures dip below 50 degrees Fahrenheit.

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Step 1

Mix the joint compound with water in a bucket. Add water incrementally. Stir the joint compound to an even consistency after each addition. Scrape the sides and the bottom of the bucket as you mix to keep the mixture consistent. Stop adding water when the joint compound is the consistency of thick peanut butter.

Step 2

Cover the drywall joint with a thick layer of joint compound using a 4-inch mud knife.

Step 3

Leave the joint compound to set for the manufacturer-recommended amount of time. Read the label carefully as the set time for joint compounds vary widely. Most setting-type joint compounds come in 20-, 45- and 90-minute set times.

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Step 4

Place a strip of joint tape over the drywall joint.

Step 5

Apply a thin layer of joint compound over the joint tape. Draw the mud knife firmly over the joint tape.

Step 6

Leave the joint compound to set for the manufacturer-recommended amount of time.

Step 7

Apply a second thin layer of joint compound with a 6-inch mud knife. Extend it 2 inches beyond the first layer.

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Step 8

Leave the joint compound to set for the manufacturer-recommended amount of time.

Step 9

Apply a second thin layer of joint compound with an 8-inch mud knife. Extend it 2 inches beyond the first layer.

Step 10

Leave the final layer of joint compound to dry for the manufacturer-recommended amount of time.

Step 11

Sand out any uneven spots in the joint compound with 80-grit sandpaper.

Step 12

Paint the drywall with one to two coats of exterior latex paint to protect the joint compound from moisture.

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references

Meg Butler

Based in Houston, Texas, Meg Butler is a professional farmer, house flipper and landscaper. When not busy learning about homes and appliances she's sharing that knowledge. Butler began blogging, editing and writing in 2000. Her work has appered in the "Houston Press" and several other publications. She has an A.A. in journalism and a B.A. in history from New York University.