Expert: Greg Scholl - 2/18/2009

Question
My son-in-law is building a house and has just installed a mahogany exterior
front door that he wishes to stain walnut and finish.  What is the best wood filler
to use for cracks pre-finishing?  I always use an oil based wiping stain applied
with a rag.  Anything else that should be considered? What type of finish is best
for an exposed exterior door?

Answer
Hi Jim, are there cracks in the new door? If you mean the small gaps between machined pieces, I wouldn't fill these, as the door will move from season to season, and the filler will look cruddy, as well as prevent finish from entering these areas which is important. A typical floating panel door assembly needs to be flooded with finish enough to enter all the hidden areas, and end grain, to seal properly against water permeation when applied. A pigmented oil stain would be ok, but apply it thinly and wipe each coat off thoroughly, as you don't want to interfere with adhesion of the topcoats. And certainly use stains and products specifically designed to work with each other. You can use an Exterior Spar varnish, or Spar Urethane, which are a Glossy surface finish that will eventually fail and start peeling and flaking, or look into a penetrating finish like Cabot,Flood or Waterlox...these have the advantage of soaking into the wood and hardening from within instead of sitting on top of the wood as a film. With the new VOC regulations in the Northeast and elsewhere, many of the better finishing products are not available anymore in their original formulas....this is very frustrating for many of us who have used and recommended these products for years, and we're having to re-educate ourselves and choose from a limited supply, with less durability and a  little track record...not a good place to be in. Companies like Sikkens, Flood, etc, who have made some of the best exterior products, can't be bought anymore in their original, and time tested formulations. The real advantage to something like Waterlox is the ability to re-apply without much prep. I wouldn't hesitate to contact any or all of these manufacturers and speak to them about the products and a recommendation. Luckily they all have experts of their own on staff to help....hope that helps a little- Greg

http://www.waterlox.com/desktopmodules/fathomecom/catalog/category.aspx?tabid=42...

http://www.cabotstain.com/products/product-
type/Clear%20and%20Translucent%20Coatings.html

http://www.flood.com/flood/Products/Exterior/

Hey Jim, if you can finish the door horizontally, it is always better, especially for getting the bottom and top coated properly, especially any exposed end grain. Best of luck- Greg