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Millwork of Urethane – Limitations

Limitations of Urethane Millwork

Many of the pieces of urethane millwork - especially exterior pieces - look as if they could support weight. Columns are examples of this. Urethane millwork is NON-structural. This means they are for decorative purposes only.

Each manufacturer often has unique installation procedures. They are not difficult to follow. However, I recommend that you read the instructions twice before attempting to install your millwork or before the carpenter does. You want to make sure that it is done correctly!

Keep the millwork out of direct, hot sunlight while working with it. Urethane millwork can and does expand. This expansion needs to be accounted for. If you install a piece that has lots of retained heat and has already expanded, it may shrink and leave a gap. The manufacturers give you specific instructions on how to deal with this.

Urethane and Vinyl Siding

Urethane door surrounds and other trim pieces look great with vinyl siding. You can get into problems though if you are not careful. When you install urethane over vinyl, you need to incorporate an extra step in the fastening process.

Vinyl siding expands and contracts with changes in temperature. If you nail it tightly in place, it will buckle when it gets hot. Nails that penetrate from the urethane into vinyl siding need to pass through enlarged holes in the vinyl siding. To achieve this, you have to tack the urethane trim in place so it makes holes in the vinyl. You then remove the urethane trim and enlarge the holes in the vinyl. It is best to enlarge the holes at least three times the diameter of the nail shaft.

Once all the holes are drilled out, you then fill them with caulk. Immediately, reposition the urethane trim and drive the nails into the enlarged, caulked holes.

Patience and Measuring

Some urethane millwork trim is expensive. If you make a mistake, you often have an expensive scrap piece of trim. Take your time when measuring and cutting.

Many of the products are supposed to be cut long and snapped into position. Sometimes you are supposed to cut the pieces 1/4 inch extra for every 10 feet of length. Remember, you can always cut off more! Cut a piece a little long and test fit it. If you are working with another person, ALWAYS calibrate your tape measures! If the hooked end is bent (from dropping it), you can be off by 1/8 to 1/4 inch easily!

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