All wood products will eventually decay and in this howto we will cover how you can repair a rotted door jam and molding.
The first thing you have to do is find the problem. When decay sets in on painted surfaces you will often find that the piece will look relatively ok from the outside but because the non-painted surfaces may have absorbed water over months and years the damage is likely to happen from behind.
Inspecting your home in the fall is a great time to catch and repair damage like this before winter comes and the problem can not be addressed. Paint, caulk and filler require a temperature of 70°F to dry and cure.
How To make the repair
The first thing we need to do is cut out the damage.
Make a level horizontal mark on the molding that you will be removing.
Cut high enough that you are sure to remove about an inch of good material.
Square cuts will aid you in replacing the molding use a speed square if you can.
You can use a jigsaw or a hand saw to perform the work. Here we need to pull back a piece of corner molding that forms the joint for our vinyl siding.
When working with vinyl siding be careful not to bend it past the point where a permanent crease will form. If necessary protect the siding from saw damage by inserting a piece of metal.
Inspect the molding and make sure that all of the rotted area has been removed.
Here you can see that not only the molding but part of the lower jam has been eaten away by water damage.
We will use a sharp carpenters chisel to remove the damaged wood on the jam.
While repairing the damaged piece you should inspect the area and try to find the reason for the damage. If possible repair the main cause of the problem.
Replacing the damaged wood
You will need a piece of molding that closely matches the original shape used on your door.
Take the piece that you cut from the door to your local building supply center and match up the part. Purchase enough molding that you can make a mistake and not have to return to the store.
Using the piece that you removed mark the length of new molding and dry fit it in your opening.
We will use a piece of 1x 1/2″ scrap strapping to fill the area of damage on the door jam.
Coated and Galvanized Fasteners
Since we know the area is a water problem it is best to use either galvanized nails or coated screws.
Here you can see a few of the 3 inch coated deck screws that will position the molding. The actual fastening of the molding is in 2 upper screws while the lower screws simply hold the molding in position.
The small piece of wood that will replace damage on the jam section is held in place by two hot dipped galvanized brad nails.
You should counter sink the heads of screws and use a center punch to drive the heads of nails beneath the surface of the wood.
Filler and Caulking
The pieces that we are using to replace the damaged molding will not match perfectly so we will need to fill the gaps with body filler.
You can also use wood filler if it is rated for exterior use or simply use caulk to fill the gaps.
Protect the areas around the repair with tape. Newspaper is also good if you think you will need it.
Mix the filler and apply it to the surface forcing it as deep into the cracks as possible.
Sand the area with 100 grit sand paper to shape the filler to the repair.
Chisels are also good to remove and shape filler on moldings. The sharper the chisel the better.
You may need a second coat of filler to fix any low areas.
Once the filler has cured for at least 4 hours and you are happy with your work you can paint and caulk the jam as needed.
If you need to let the piece cure over night remember to place the vinyl siding back in its original location. Vinyl that sits in a bent position over night or for an extended time will retain that shape and may not fit snug against your jam the next day.