What is best way to seal a cedar pergola?
The best way to seal a cedar pergola is prior to assembly. It’s always easier and less messy to seal a pergola prior to construction.
If your pergola is already constructed, you can still simply use a rag, paint brush, roller or sprayer to apply wood sealer or Linseed oil for a clear seal. Just make sure and protect anything around the pergola, that you don’t want to seal, with a cover.
Most stains also contain a sealer to help protect the stain and wood from fading, so you can likely skip this step when using a quality stain.