Expert: Bruce E. Johnson - 6/25/2009

Question
Our builder is renovating our house and put in a massive oak lintel in a one story extension over 2 sets of French windows.  (They are not sliding doors but open into the room) with a vertical T bar of massive oak beam between the two sets of doors.  The doors get quite a lot of strong sun for about 4 hours per day.  The outside of the T bar is cracking and now the inside of the T bar has long cracks.  Our builder says this is due to the Sun, How can this be if it is cracking on the inside also.  Out builder says that the T bar is not carrying any weight as that is on the Lintel.  The builder has already had to re hang the doors due to the wood moving or twisting slightly.  Can you tell me if it is the sun causing the cracking.  Many thanks.

Answer
Hi cynthia, I can't tell you if the sun is causing the cracking because I don't know how much sun it gets or how hot it gets.  I do know that wood will shrink and crack if it is not cured or cared for properly.  Big beams or posts are usually logs that are plain sawn, in which the two sets of opposing sides are cut flat to form the width and breadth of the beam and the beam or post is made up of the heart of the tree.  If the log is large enough it may be sawn in half and each half squared into a beam or post.  How the lumber is milled determines its characteristics.  A beam made from a single core tree will have a tendency to twist during the curing process while a beam made from cross cutting a tree will tend to cup during the process.  All lumber will crack or split if it is not cured properly or treated or sealed properly.  I just saw an article about Joan Rivers multimillion dollar home and in the article there were photos of large beams in her bedroom that had large horizontal cracks in them so it is not uncommon and in some cases preferred for the rustic look.  In your case, the wood was probably not cured properly before and after milling and the sun shining on it is just speeding up the curing process causing cracks.  Oak needs to cure a long time before milling and then dried and cured properly after milling, unfortunately in our fast paced society, some mills don't follow all of the curing procedures for structural timber as they do for the more premium cabinet and furniture grades.  Often times on our projects we use laminated lumber for big beams to get away from the checking and cracking associated with natural lumber. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonsulting.com