How to Seal Exterior Spackle
Spackle, or spackling paste, is a type of filler available in many forms. Interior surfaces often require lightweight spackle, while outdoor spackle is heavier. This is because the exterior of the home it's meant for is continually exposed to direct sunlight, higher temperatures, greater humidity extremes, plus wind, hail, sleet, rain, snow, and in many cases blowing sand and dirt. So, you can see what it's up against out there. Outdoor spackle has to be more flexible and able to resist the onslaught of Mother Nature than indoor spackle.
Choose the Right Spackle
Modern-day spackling materials are much lighter in weight, however, you can still buy oil or latex spackle if that's what you prefer to use, but they are heavier and are not used much anymore. Heavier spackle will give you a more irregular finish because it's not re-wettable after it dries and it does not dissolve in water. The newer spackling materials are shrunk free and so they can be used to fill small areas and sanding is kept to a minimum. Spackle dries very quickly, sands very well, and can be coated with latex or oil paint once dry. The key to getting a seamless wall when done is to sand it and apply primer properly.
Sand Down the Area
The area that you intend to spackle must be sanded down before the primer is applied. You can accomplish this with some sanding paper or a sander. Makes sure that the surface is completely clean of sanding dust before continuing. Remember that spackle is not intended to be used to float drywall joints or for holes that are very deep.
Apply a Primer
You must prime all bare wood surfaces before you lay spackle upon them and it's a common mistake not to do so. If you do not prime the wood the surface will be irregular, there will be dull spots on the finish, and any paint that is applied will not allow itself to be blended correctly. There might even be shiny spots on the finished paint. It is also important to use the right kind of primer. Bare wood and rusted metal use different kinds of primers. If there are knotholes in the wood, prime them with material that can seal in the sap. Bare wood might take out moisture from the patch. If this happens, the surface might dry out and cracks might form around it. So, first prime the wood, let it dry, and then finally you can apply the spackle. Do not use stain-blocking, or stain-kill type primers because this will cause high-gloss areas called shiners to appear on the wall. These are spots where the paint is too glossy. The best type of primer to use is the finish paint itself. There is also a kind of primer called PVA, or polyvinyl acetate, which is a new type of drywall primer.
Apply Paint if Applicable
To seal exterior spackle, apply one coat of the finish paint. Then wait two hours for it to dry. Then apply another coat.
Remember to always keep the lid on your spackle can whenever it isn't in use.