Why Do They Crack?
Trim boards on the interior of the home or on the exterior, can crack and split if stress is applied, for any reason. If the home is drying out due to added dehumidification, or if the home is new and the trim boards are simply drying out, they may crack and split.
Exterior trim boards can become compromised due to water penetration or additional drying out by the sun. Any movement of trim boards can cause the wood to split especially around the areas of nail or screw attachment to the sub-surface behind the trim.
How to Repair Them
Repair of any type of crack or splitting of wood trim boards is basically accomplished by using common sense. Following are some very basic techniques to be used in repairing cracks or splitting trim boards.
- Clamp: If the side edges of the trim boards are accessible, the application of a clamp to squeeze the cracks closed is the easiest method of repair.
- Glue: Insert wood glue into the cracks and splits prior to applying the wood clamp. Use plenty of glue to ensure that the entire crack or split is filled with the glue. Once the clamp pressure is applied, the surface of the trim board can be easily cleaned with a damp rag.
- Fasteners: If the clamp can remain on the trim board for the length of time necessary for the glue to dry, this will be the best method of fixing the crack. In some cases, if you do not have enough clamps or the length of the crack is too long, the installation of additional fasteners maybe required.
- Screws: The most efficient fastener to use is a small head finish screw. These screws are extremely narrow in girth and have a very small head. Normally the head is a star type of head or philips, which can be installed with a power driver. If these small screws are used, a small drilled pilot hole is recommended to prevent additional splitting of the trim board.
- Small nails: If nails are to be used, the smallest finish nail is recommended. If possible a small pilot hole is recommended to be drilled prior to the installation of the small finish nail. In all cases, care must be taken to not destress the surface of the trim board by slipping with the screwdriver or missing with a small finish hammer.
- Take care: Finesse is recommended when repairing trim boards. Take your time and use common sense when selecting fasteners. The smaller the fastener the better to prevent future splitting.
- If the trim board must be squeezed without the assistance of a wood clamp, a small pilot hole should be drilled into the edge of the trim board. This pilot hole will be used to install a slightly larger nail or screw. Again, care is necessary to prevent additional splitting.
- Seal: Once the crack or split is closed and secured it is highly recommended that several coats of sealer, paint or poly be applied over the crack to attempt to reduce the amount of moisture that will be able to enter the crack. Remember, in most cases, moisture and then excessive drying will expand and contract the repaired crack or split and cause them to reopen.
Inside & Outside
The technique of repairing either interior or exterior trim is basically the same. It is very important that the time is taken to properly and carefully apply the glue, close the crack and secure the board. You will cause additional splitting or cracking, if too large a fastener is used or the installation of the fastener is too aggressive, like heavy pounding or screwing of the finish screw too deep, into the surface of the trim board.
If the crack or split cannot be closed, they can be filled with a wood putty or filler. These fillers are easily sanded and can be blended into the surface of the trim board.
If you feel that there are too many cracks and splits in all of the trim boards around the home, a professional painter will make all, or most of these imperfections disappear. In most instances a cracked or split trim board is merely cosmetic, and will not cause any structural issues. However, a tight and closed trim board surface is certainly more presentable than one that is cracked and split.
Remember, take your time, use smaller fasteners, plenty of glue, and be extremely gentle when repairing trim board cracks and splits.