Filling Exterior Wood

On exterior surfaces, water can run off from wood that you have filled and sanded smooth.  You should fill all holes and cracks, and sand them down to compensate for this fact.  This prevents water from penetrating and causing structural damage to the house.

A number of different wood fillers are available, but in two basic categories.  One type is a mixture of hardeners or water, which you then sand smooth when it is dry; the other type is flexible, to allow for movement.

All-purpose powder fillers applied to the wood’s surface can cover small nicks and holes.  You do this by pouring a small amount of the powder onto a filler board and slowly add water.  Mix it in with a filler knife until you achieve a smooth, but sturdy consistency.

The filler is then pressed firmly into the hole and left slightly proud of the surface. Usually the filling knife has to be moved across the surface of the filler several times to ensure that it is firmly in place in the hole.

You then let the filler dry for an hour or so before sanding it back, making it flush with the surrounding surface.

When dealing with deeper holes, it may be necessary to build up layers of filler slowly to get a perfectly smooth finish.

When sanding the protruding surface of the filler down after it has dried, use a coarse grain of sandpaper first, and gradually move up to the finest grade.  Once the surface is completely smooth, you can protect it with exterior paint or resin.

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