Usage of Finger Jointed Lumber for Rafters and an OSB question

It is my understanding that finger jointed lumber should only be used in vertical studs and that it should not be used for rafters. When looking over a friends new construction home I noticed widespread usage of finger jointed lumber for the rafters. Is my understanding correct? If so, it seems that this could lead to premature failure of the roof.

As a secondary question - is there anything to be concerned about if the builder installed about 50% of the OSB sheathing with the “This Side Up” stamp facing down. I don’t believe this compromises the strength of the roof but I would not mind a second opinion before I report back to my friend.

Thanks in advance,


Finger jointed lumber comes in two grades … one for stud use only (compression only) and one for joists/rafters (bending applications). Check the grade mark on the lumber. Although using correctly graded lumber is acceptable in the industry, I think using that for roof rafters where it may get wet over time could present future issues.

For the panels I don’t think it really matters which side the stamp is on from a structural point of view, but when installed with that mark up the top surface offers some skid resistance, and the grade mark is more visible from below for building inspectors. See the following APA guide


Thank you very much. That was exactly what I needed.


If you shake and spin OSB (Oriented Strand Board) really hard does it become DSB (Dis-oriented Strand Board)? :smiley:


LOL … funny stuff. But I think it might actually become the structural equivalent of a wet napkin … :slight_smile:

P.S. I meant to also post the following file on panel installation … :wink:

From the peanut gallery;

This side up has a reason if you do not want to slide off the roof.

Finger joint on roof rafters, I would never reccomend it and don’t care what manufacturers Engineers will try to convince me. I have worked with too many fingure joint products and experience their capacities. Dont’ try to use finger joint trim on a radius of 26.5 feet because they will break or open up in about two days. Not good in tension and the modulus of elasticity is very poor. Grade E when I was in school an that does not mean excellent.
I would also have my doubts about finger joint studs even though it is in compression.
Come to think about it, my window sills are fingur jointed and fall apart every year and have to paint it. Well, maybe the glues are better today than they were 30 years ago. Who knows.

Marcel :slight_smile: :slight_smile:

So… rafters have to be level to achieve correct nailing?

They mean (reasonably) level from rafter to rafter (see the diagram on Pg 1 of the last link I gave) … not along the rafter … :wink: