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Cornice Moulding Installation Instructions We
recommend that all first time installers, sub-contractors and do-it-yourselfers
read the following instructions for the best installation results.
Technical MDF may be manually hand nailed, or fastened with pressurized air pneumatic finish nailer. If your installation method of choice is manually hand nailing, pre-drilling is suggested, but not necessary. If your choice is a pneumatic nailer, the recommended air pressure should be 98 to 110 PSI. Installers who have not worked with MDF before should test and adjust the air pressure as needed for their specific equipment. The best fasteners are 15 to 18 gauge brad and pin nails. The type of finish nailer used, is up to the installer. It will vary based upon personal preference. Carbide tip blades are recommended. They deliver the finest and cleanest cuts and have longer tool life before needing to be sharpened or replaced. If nailing creates a "blow out" or a "puckering" effect with
proper pressure and nail selection, rotate the fastener to a 90 degree angle, or
perpendicular with the moulding and apply the nail. Staples and "T" nails may
cause a puckering effect and are not recommended.
A miter joint is recommended for inside and outside moulding
corners, as well as chair rails, baseboards, window and door casings. A miter
cut is made straight across the grain of the wood at any angle other than 90°.
The most common miter cut is at 45° where two pieces join together to form a 90°
angle. These cuts should typically be made with a compound miter saw. The use of
these types of chop saws will give you the best and most accurate results. The
reason for this is that this types of saw will allow you to do a miter cut, as
well as a bevel cut, all in one stroke action. Keep in mind that all crown
moulding is not at a 45° angle when installing, it is therefore recommended that
the degree of moulding, as well as the degree of your wall angle be determined.
Once this is completed look up these angles in the chart provided, the chart
will give you the angle settings for your chop saw.
The best method to bring miters together starts with an accurate, clean cut. Add a bead of MDF glue (REGULAR CARPENTER’S GLUE WILL NOT WORK) and apply one brad nail through the top of the joint down. This will pull and keep the miter together. A common mishap when edge nailing is splitting in a plane parallel to the surface. Using the finer gauge brad or pin will alleviate this problem.
When installing long lengths of crown, do not cut the moulding too tight. Leave a small gap about the size of a credit card at the square end. The coped end will then cover this and a small amount of caulking (ALEX PLUS DAP or SPACKLING DAP) will complete the corner. When a splice is required, use a 30 degree angle. Glue and pin nail the splice to prevent any separation. Like all wood products, MDF absorbs and desorbs moisture with changes in relative humidity. The normal range of interior humidity is 40% to 80%. The industry standard for maximum expansion and contraction of MDF due to changes in relative humidity from 40% to 85% is .3%. Thus, some expansion and contraction of MDF mouldings should be expected. All areas must be free of debris and door openings must be plumb and square. Suggested tools needed:
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