difference between structural pressure treated lumber & just reg.

jaxkewlJune 1, 2009

what is the difference, if any, between structural pressure treated lumber and regular pressure treated lumber? i know the structurual PT has those little slits or lines on it and the regular does not. At lowes they sell both kinds, very little in price difference, but is the structural PT that much "stronger" or has more chemicals during the PT process? i'll be making a deck roof made out of wood and those slits are unslightly. you can see them on the posts and rafters. could i get away with just using regular PT lumber? There will be no ground contact and I'll be using a ledger board attached to the house frame work.

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aidan_m

You wouldn't be able to tell the difference between PT #1 select structural and regular PT #2. Lumber has an ink stamp from the sawmill indicating the grade, species, sawmill, etc. Usually the presure treating process covers up the original stamp.

The little dashes or color of the chemical treatment do not have anything to do with structural grade. Lowes and Home Depot do not sell any #1 structural grade lumber, with the possible exception of 4x6 and larger timbers. You need to look at the stamp to know for sure. The PT at lowes and HD are definitely not structural grade.

If I need #1 select structural PT lumber, I special order it. The sawmill grades the wood #1 and then sends it for chemical treatment. The large PT beams are often already #1, but in order to get PT 2x material in #1, it basically has to be special order.

Don't waste your time even asking the people at Lowes or HD any of these questions. They are probably the ones who told you about looking at the little dashes.

    Bookmark   June 1, 2009 at 12:58PM
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john_hyatt

John agrees with Aidan,again, the box stores sell the low grade pt lumber not made for ground contact in other words you would be just as well off using regular yellow pine.

Look for a lumber yard that sells .40 or ground contact material.

Over here I can get #1 pt yellow pine the knot grade is a little better and its been klin dried twice so really it is a little more structural than the #2 grade but your not going to find any of that in the box stores. J.

    Bookmark   June 1, 2009 at 4:47PM
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