Failing Paint and Caulking - What is hidden underneath?

Caulking and paint need yearly maintenance to ensure that it is still protecting your house. A common spot to find hidden damage is at exposed wood trim, especially at areas that have a latex caulk sealing a gap. Caulking with a coat of paint is pretty good protection for wood, but  once it fails water has an easy path to wood and can cause hidden damage.

Look for bubbling areas of paint and dried out looking cracks in the caulking between joints.

You can see the failing paint and shrinking caulking in the above pictures. A good visual clue to look for is "bubbling" areas of paint on a flat surface. You will also see cracked looking caulking in between wood joints. Think like a drop of water - it wants to go with gravity and the path of least resistance. This railing was pretty sound at the top but had significant damage towards the bottom of the slope. 

Damage is easy to see the farther down the slope you go. Water damage generally follows gravity and the path of least resistance.

Light pressure probing with a knife reveals the damage under an area of failing paint.

Just a little bit of probing at a bubbling area reveals hidden damage. I used fairly light pressure here and the knife slid right in to the wood. You can see the hidden rot underneath. This has been going on for a while. It's likely that the previous homeowner painted over a failing area of paint without fixing the underlying damage. 

The bottom of the railing with extensive rot. This railing needs to be replaced.

Pretty rotten. That knife went all the way through.

Light pressure with probing sunk the knife in to the failing wood.