2008 Issue 6

Building Blocks
by William North
EXTERIOR FACTS, IDEAS AND SOLUTIONS

Have PVC Trim boards become the product of choice?

Many condominiums in New England are suffering from a wood crisis. A crisis that can be summed up in one word -  Failure. Wood that was installed in the 80’s is being replaced much sooner than anyone would have forecast 15 years ago. The wood is rotting, grain delaminating, failing at finger joints, warping, eroding and worse. The end result is that repaint cycles for trim are too often shrinking to 2 or 3 years. Preparation remedies are expensive. Often the cheapest solution is to simply replace the material. As might be expected, when an unplanned expense grows, someone often asks the obvious question: “What is going to make today’s new wood last longer than the boards being replaced?” Lack of confidence that there is a certain answer to this question has driven the search for the perfect alternative to wood. Enter solid PVC boards, moldings and sheet products.

Solid PVC Trim Boards are a recent improvement on an older concept; mimic wood with plastic and gain the benefits of wood without the drawbacks. The devil has been in the execution.  Most products have provided benefits but presented considerable liabilities as well. The newest generation of free foam extruded expanded rigid PVC appears to achieve the solution.

Picture a product that is rot proof, impervious to insects, can have direct contact with moisture, and can be set on grade or directly on a roof line. You can cut it like wood with the same saws and blades, nail it, glue it, cement it, drill it, edge nail it without splitting, and bend it (with heat).   

Now think of the trim on the outside of your unit. How different would the trim look today without the cracks, knots, grain cracking, tannin staining, moisture peeling, cupping, warping and eroding of the wood.

By now the cynical mind is looking for the catch. Where are the liabilities? Interviews with carpenters in the field do not yield many negatives but there are a few.

Some Considerations

The material is more expensive than standard #2 pine but is less expensive than cedar. The material does expand and contract with temperature fluctuations so it needs to be fastened properly into a sound substrate. Fasteners should be stainless steel ring shank nails installed flush with the surface of the material, do not counter sink the fasteners. Painting the materials with dark colors can enhance the expansion of the material in direct sunlight and should be avoided. The material is not recommended for use in any structural or load bearing application. As the temperature drops the impact strength declines. This means that on a cold day there might be risk of fracture if one were to strike this material with force. Pre-drilling fasteners in winter time installations is recommended.  

The material does not need priming but like any material it does need long term protection from ultra-violet light and the growth of mildew into the cut edges. The stock is colored white with titanium dioxide. The materials should be coated with a 100% acrylic latex finish coating, any lighter shade color can be selected and changed over time to accent changes in siding color schemes. The latex coating acts as a sacrificial protective coating from sun light. This is not any different from the long term performance of most materials. Factory finished coil stock, aluminum siding and vinyl siding all show erosion and wear over time from the ravishes of ultra violet light.

Next Steps

An advantage of this new product category is that material can be replaced piece-meal or wholesale, in that replaced boards will look just like wood. Piecemeal sections should be done in the longest practical lengths in full sections where possible (i.e. both sides of a corner board, all sides of a window, etc).

Any trim area on a building is an appropriate application for PVC boards or moldings. A selection of widths, thickness and moldings are available off the self. The material can be custom milled to almost any specification. Sheet stock is also available, making the replacement of plywood an attractive option.

On brick buildings, beyond the use of standard cuts, brick mould (908 casing) window trim is a stock molding designed for use around window installations.

The product selection is diverse, the material properties attractive and the process of conversion painless. If wood failure issues are creating dissatisfaction, frustration or financial stress at a property, solid PVC trim deserves serious consideration and trial, as solution options are being evaluated.

William North is President of Prime Touch Services. The company provides condominium consultation and maintenance for painting, carpentry and vinyl siding in New England.