Deck

How much end support do the beams on a deck need?

Beams rely on at least 3 1 /2 inches of end bearing to transfer their loads to the structure below (usually columns or walls).

End bearing may be poor because of

poor construction
building shifting
rot
settling columns
sagging beam

One cause of poor end support is shifting of columns that support beams. If a column shifts and rotates away from the building, a beam may lose its support at the column end. If the beam moves with the column, the end of the beam resting on the house wall may be pulled out of its pocket. Beams resting in masonry pockets should not be mortared in tightly at the ends. There should be space allowed for ventilation so that the wood can dry after it gets wet.

Beams without adequate end support may fall.

To check for problems: Where visible, look for at least 3 1 /2 inches of end bearing for beams. Probe ends of beams with a screwdriver to look for rot. Examine beams at pockets for signs of the beam having pulled out of its pocket. (The beam end may not have paint on it, or may be a different color because of less exposure to sun.) At connection points to columns, watch for evidence of movement of the beam relative to the column. Again, a section at the end of the beam may be unpainted, for example.

Many beams are clad or covered with decking and skirting. You can only see part of the assembly. Remember never to declare something to be in good condition, since there is much that may be wrong that cannot be seen. Check were possible whether beams are mechanically fastened to their supporting members below. Beams should not simply rest on the tops of the columns or pillars. This attachment is often not visible.