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Archive for August, 2010

Should I Use Polyurethane on My Pergola or Arbor?

Saturday, August 28th, 2010

Question: I just bought a brand new pergola kit from SimplyPergolas.com, and now I’m looking to add a finish to the wood.  I’m used to working with indoor furniture and woodworking and use polyurethane on most every project that I work on.  I’m wondering if polyurethan works for an outdoor project as well?

Answer: That depends.  First and foremost, there are two different types of polyurethane, one made for indoor materials and another that is specifically formulated for an outdoor application.  The outdoor version has special additives that make it suitable for withstanding the rigors of outdoor life, especially UV rays.  The second aspect of this decision is regarding the wood.  If your pergola or arbor is made from an oily wood like Shorea or Teak, then polyurethane won’t work.  A poly finish on one of these woods will act like a sealant on the wood, and then the oils will need to come to the surface at which point the poly cover will bubble and peal.  It will then be very difficult to remove.  So, if you bought a pergola kit made from Cedar or Redwood, you’ll be OK.

Which wood should I use for my pergola or arbor?

Tuesday, August 17th, 2010

There are not too many domestic woods that are suitable for an outdoor project like this.  Here’s a list of domestic woods that you’ll be able to find for your pergola or arbor.

  • Southern Yellow Pine - It’s cheap and readily available, but you’ll have to treat it for it to last more than a couple of seasons.  It also is bug food and has sap when not treated.  $3 per linear foot.
  • Douglas Fir - This strong, northwestern softwood is stable and sap-free in clear, vertical-grain cuts. Less rot resistant than red cedar and redwood.  $29 per linear foot.
  • Redwood - Premium western softwood that’s stable and sap-free. Clear grades like this are costly.  About $37.50 per linear foot
  • Eastern White Cedar - It grows on the eastern half of the US.  It’s a stable and sap-free with small, tight knots. $27.50 per linear foot.
  • Cypress - This is a tropical wood that grows in the US, and there aren’t many, it has a tan color and is related to redwood.  It is stable and sap-free. Can have small, tight knots.  $17.50 per linear foot.  This is a great wood, that has a middle range price.
  • Western Red Cedar - A Pacific Northwest wood with superior rot and insect resistance. Stable and sap-free. $6.50 per linear foot.  This is a favorite of ours because of it’s value.  Dollar for dollar, you won’t find a better wood for performance and looks.