When to Pre-Drill

Ask twenty do-it-yourselfers how important pre-drilling is, chances are you’ll get at least ten different answers.

So, is pre-drilling necessary or just an added step almost never needed? That depends on many factors.

You need to pre-drill if:

  • You are using green wood. If the piece of wood you are drilling is heavy for it’s size, it is likely green, or young, wood OR
  • You are using treated wood. Treated wood is usually used for outdoor structures or decks OR
  • You are using hardwood. Birch, cherry, mahogany, maple, oak, poplar, rosewood, teak and walnut are all hardwoods OR
  • Your final hole will be larger than 3/8” OR
  • The wood you are using has been stored in humidity greater than 20% for more than 24 hours before drilling OR
  • You want to pre-drill.

You do not need to pre-drill if:

  • You are using dry wood that has not been pressure or chemically treated AND
  • You are using softwood like pine, cedar or redwood AND
  • The final hole will be smaller than 3/8” AND
  • The wood has been stored in dry conditions for more than 24 hours AND
  • You don’t want to.

Pre-drilling Tips

  • If you don’t pre-drill treated or green wood, it will likely split when it dries.
  • Hardwood typically takes years to completely dry so you should always pre-drill hardwood, since it’s possible it still has drying to do.
  • Holes larger than 3/8” can put undo stress on wood. If you pre–drill these holes before inserting a screw or nail, most of the wood will be removed from the hole before nail or screw is inserted, reducing stress.
  • Always pre-drill with a bit slightly smaller than the final hole.
  • If the final hole will be 3/4” or larger, pre-drill in increments of 1/4?. Example: pre-drill with 1/4” bit, then 1/2? bit, then 5/8” or 11/16” bit.