Checking or longitudinal cracks in ceiling beams

[tlc...]

We installed 8 6x12 white pine beams 15 ft. long in the living room of our new home built 1 year and six months ago. The beams are exposed about eight feet high with 6x6 white pine purlins 6 ft. long connecting them to the sloped ceiling. The beams were finished with Minwax stain and three coats of polyurethane. No finish was applied to the end grain.

We have noticed checking or longitudinal cracks forming in some of the beams over the last year or so.

Any ideas on how long this might continue or when the 'checking' process will stop?

The house is humidity controlled to 45-50% RH year around.

The beams are not an integral part of the house structure so strength is not a prime concern. I am interested in when the process will stop so I can stain the cracks and improve the appearance.

Regards; tlc...

[George]

When the inner strains are fully relieved is the best answer. At that size, it's dollars to donuts you've got a boxed heart. The radial splits will go to the heart and stop. Structurally it's probably a push, the dryer wood being more resistant to deformation than wet.

Stain when the opportunity arises, poly after you haven't stained for six months.