Another common problem, closely related to sill deterioration is rot at the bottoms of posts. This can be caused by rot in the sill traveling into the post, but it can also be caused by water getting through damaged or missing siding and trim boards. The natural tendency of water is to flow downward and it accumulates where the post meets the sill. This causes the post to rot from the bottom up. Often this is not discovered until sill replacement is undertaken and the post bottoms are exposed showing missing tenons or hollowed out posts. Often the post appears to be intact and undamaged but is found to be rotted as far as four to five feet up on the inside depending on the age of the barn and the species of the timber. In the worst cases the post is rotted from top to bottom due to water coming in through the roof or along the eave. This condition is typically visible from inside the barn without removal of siding or connecting timbers.
Post repair or replacement is often somewhat complex. With the exception of interior posts, the timber framer will most likely have to deal with mortice and tenon connections at the top and bottom of the post, as well as connections along its length for siding girts, tie beams and braces. It is not uncommon to find eleven or twelve mortice and tenon joints in a corner post. Dealing with these connections is a matter of analyzing the situation and designing a repair well suited to it. Post bottom repairs can be done by simply stabilizing the upper part of the post and scarfing on a new section at the bottom. If the damaged area includes wall girts or braces, free tenons may be required (see photo to right). If the entire post needs to be replaced it may be necessary to jack and crib the corner of the barn which allows the walls to be spread enough to remove the post and insert a replacement.