I have wood pergola columns connecting to my house through fixtures which are fitted into grooves in the wood. The wood was cut slightly too short (or due to small variations in the wall), there is a small gap about 1–2 centimeters in some places. I want to fill the gap so that the metal fixture won't be visible and the wood "end" will be flush with the wall so water won't get between the column and the wall.
In this picture you might be able to see the small gap I need to fill. In some other places the gap is larger (in this case it might be barely visible)
Best Answer
How to correct for the gaps is a challenge if you just decide to "stick something in there" such as caulk or shims. I say that because anything you do along those lines is going to look crappy and kludged up.
The best solution would be to do a re-install by carefully measuring each individual piece and cutting it to the correct length. Done that way then a very small bead of exterior type caulk can be used to seal off the end of the beam to the wall if needed.
One possible solution that may work for the existing installation is to get some trim pieces that are cut and fitted around the ends of the beam and up to the wall to cover the gap. It would look something like this:
The trim pieces could then be sealed to the wall with caulk if so needed.