As a finish carpentry subcontractor, I've been thrown a lot of
curves lately by the builders in my area. Curved walls, turret
entries, and oval hallway soffits are becoming the norm. A few
years ago, our crew might have used flexible baseboard a couple
of times a year, but now we see curves and use all types of
flexible moldings on about half the houses we trim.
When I first used flexible baseboard about 12 years ago, on a
cold day it was about as pliable as a frozen garden hose. It
had to be warmed up before installation on a cold job site, and
even then it was difficult to nail and would sometimes crack.
Though it's still stiffer in the cold and more flexible in a
warmer environment, the material now available is much
better.
Flexible baseboard is easily site-bent
to almost any required curve, but most crown molding and casing
must be custom made to fit the situation.
Ordering Flexible Trim
There are three major manufacturers of flexible
polyester-resin moldings similar to what I use: ResinArt, Flex
Trim, and Flex Moulding (see "Sources of Supply," page two of
article). All three supply molding profiles in a large variety
of patterns and sizes to match common wood moldings. In
general, I think of flexible molding as a generic product and
order it through my regular millwork suppliers. Most of my
experience has been with ResinArt because it has the shortest
lead time at my supplier.
Stain grade available. So
far, I've worked only with paint-grade flexible molding, but
grain-embossed stain-grade material is also available. Most
makers offer a single style of grain-embossed material, but
DuraFlex offers a choice of smooth, oak, and pine
surfaces.
According to the manufacturers, staining requires a heavily
pigmented gel-type stain and a protective topcoat with a clear
finish. Unlike the process with wood molding, finishing must
take place after installation; otherwise, the finish will peel
and distort as the material is handled.
Manufacturers also offer accessories like simulated carvings,
capitals, medallions, and other appliqués. My work is
strictly indoors, but these flexible products can also be used
outside. I haven't seen any claims made about UV resistance,
but manufacturers say they are insect-proof, moisture-proof,
and resistant to extreme heat and cold.
When I'm ordering flexible moldings, I always tell my supplier
whether I'll be matching MDF or finger-jointed trim. The MDF
trim is a hair thicker, and, because the flexible moldings are
made to order, the manufacturer can account for that. This
means I can avoid a lot of laborious sanding or shimming on
site to get the profiles to match.
Flex Moulding offers Superflex, a very supple material for
tight bends, though we've found that it bends too easily for
most applications. In situations where the framing or drywall
work is irregular, it actually conforms to dips and bumps. The
standard-flex products bridge such inconsistencies, producing a
more uniform curve along the wall. Although the standard
products we use all have similar flexibility, temperature can
affect how easy they are to work with. On cool mornings, I'll
place the stiff material in the sunny driveway for a couple of
hours to soften it up.
Cutting, Finishing, and
Fastening
Flexible molding cuts easily with regular woodworking
equipment, but positioning and handling the material can be a
challenge. It takes a little time to get used to, but we've
found a few techniques that help. Basically, it comes down to
extra support, sometimes in the form of continuous support at
your miter saw station or provided by a jig.
When it comes to installation, the consensus among the various
manufacturers is that gluing is the way to go and that nails
and screws should be kept to a minimum. To prevent distortion
along the material's edge caused by fasteners, manufacturers
suggest using super-type glues with a set time of about two
minutes and even a spray accelerator. So far, I've had good
luck with construction adhesive and pneumatic finish nails and
brads. It's important to nail carefully, however. Nailing too
close to an edge can cause a bump along the edge, and hitting
the hollow of the crown can collapse the material. After
establishing the proper nailing pattern, I rely heavily on
pneumatic fasteners and use construction adhesive only at
joints. I haven't tried hand nailing, but it seems like it
would require a lot of predrilling and patience. I suppose the
fast-setting glues would help a lot if you don't have access to
air tools.
Baseboard and Chair Rail
Flexible baseboard is an off-the-shelf material at most
dedicated millwork suppliers, but you probably won't find it at
the home center or standard lumberyard. My supplier carries it
in three styles for matching the most common baseboard profiles
in my area. My supplier also stocks chair rail, which we find
useful for many trim details, in two or three styles. One of
our projects used flexible chair rail for simulated wainscoting
with arch-topped panels. But chair rail like that requires a
special order, because the molding is curved on the wider, flat
side, like casing.
Flexible baseboard is the simplest product to use. Because
it's no more than 3/4 inch thick, it can bend to all the wall
contours we routinely see, down to inside and outside radii of
less than a foot. Although Flex Trim claims it can provide
endless lengths by special order, the boxes we get from
ResinArt contain rolls from about 7 feet to 12 feet long; I
think anything longer would be too unwieldy.
Square cuts and miters. A
square cut on baseboard can be made by simply laying it flat on
your miter saw and letting the far end fall where it may. You
can cut miters in the same position using the bevel feature of
a compound saw, but we usually cut baseboard miters in the
normal upright position with the flexible material sandwiched
between two pieces of scrap similar in height. The scrap
prevents saw pressure from collapsing or distorting the
material as it's cut. Odd angles are the norm when working with
curves, so test fitting and recuts are part of the routine.
Once I've cut one end, I hold the piece in place and mark the
next cut. Trying to measure along a curve is generally awkward
and inaccurate.
Curves and straight runs. Of
course, flexible baseboard can also make a straight run, so we
sometimes avoid a splice by continuing the material along a
straight section to the next curve. Flex costs nearly ten times
the price of the MDF trim material we commonly use, so we try
to limit this practice. Most inside-radius situations allow me
to snap a slightly long, square-cut flex piece into place
between the two square cuts at each end for a tight fit. Most
outside-radius situations require using more traditional scarf
joint, but we like 30-degree joints instead of 45 degrees. The
more acute angle matches up better.
Unlike crown, where we use brads, on baseboard we use heavier,
15-gauge finish nails. The sturdier nails hold better, and
baseboard doesn't have the delicate edges of crown molding. But
we still keep nails away from the edges, and nail top and
bottom for adequate holding.
Casing
Because curved casings for doors and windows are bent on the
wider flat side, they are typically made to order. We order our
flexible moldings through our millwork supplier, who can
usually get custom orders in about a week.
Custom curves. Ordering
flexible casing in a quarter, half, or full circle is a fairly
straightforward process. The Flex Trim website gives
information on ordering and also explains how much a curved
molding can deviate from its designed radius. Wider patterns
and smaller radii are less forgiving than narrower patterns and
larger radii. What I find interesting are the possibilities
with ovals, ellipses, and other irregular radii. If you can
describe your project with a good drawing or template, it can
be made to order.
Fitting curved casings.
Installing a half-circle of casing over an arched opening is
fairly simple because the side casing is cut square at the top.
To start, I lay out the inside line of the arch from leg to leg
with a set of trammel points. Along that line I then set a
series of finish nails on which the flexible casing can rest.
With the casing hanging from the nails and draped over the side
casings, I mark its length. The first cut is laid out by simply
marking where the flex and rigid casing meet on the inside and
outside edges. I usually make the first cut with a handsaw or
small circular saw. When I'm happy with the first cut, and have
the material back in position, I mark the second cut. Thinking
slightly long is good in a situation like this. Although most
of our jobs use MDF casing, we use the same process for
stain-grade material.
Crown
It's a good thing I like working with crown, because
installing crown molding on curved surfaces has proven to be a
big challenge. I recently finished a small task where the
framer didn't follow the plans and the millwork salesman's
measurement of the subsequent "custom" work -- an oval ceiling
soffit -- was off just enough to create a problem. It turned
out that I was trying to work with material made to a radius of
1 1/2 inches less than I needed. As I attempted to position the
crown along the wall, the top edge would pull away from the
ceiling. By the time the new material arrived, installation
seemed easy. The lesson is that flexible crown is not very
forgiving and must be ordered accurately. Because we work in
production housing, ordering in advance from the plans is a
necessary part of the process. As long as everyone builds to
the plans, there's no need to field-measure, but
double-checking can prevent time-consuming and expensive
mistakes.
The radii on the plans we get are called out as a rough
measure, so we compensate for drywall thickness to make our
orders more accurate. The drywallers in our area bend two
layers of 1/4-inch gypsum board to make the curves, so
adjusting the radius 1/2 inch makes the pieces fit better. It's
important to remember that you subtract 1/2 inch for inside
curves, but add 1/2 inch for outside curves.
Flexible crown molding can be manufactured with an irregular
radius (as in ovals and ellipses, for example), and the profile
can be oriented upside down from standard if desired. But
irregular radii will require a template or drawing, and
upside-down profiles require special instructions on the
supplier's order sheet.