Introduction to Interior Trimwork - Canadian Woodworking Magazine

Home Improvement: Learn about the terms, tools, materials, and equipment necessary for installing or replacing interior trimwork.

Introduction to Interior Trimwork

Introduction to Interior Trimwork

Illustrations by Len Churchill (Photo Lead by
There are many reasons why you might want to consider adding or upgrading trim in your home. Adding trim judiciously to the inside of your home is a great way to enhance the appearance of just about any room. Crown moulding, in particular, along with built-up baseboards, can soften the look of a room, while adding character – and even a touch of glamour.
You get a lot of bang for your buck – the materials used in trimwork are relatively inexpensive compared to other home improvement projects. Most trim can be competently installed by the average DIYer, generally in less time than it takes to complete other projects.
Trim isn’t only decorative; it’s also functional, helping to protect walls from dings and dents, whether it’s kids at play, repositioning furniture, or vacuuming the floors.
Besides adding aesthetic value to your home, it’s likely to have a positive effect on your home’s resale value, and how quickly it sells.
Plan for Success
As with most home improvement projects, there is a lot to be gained in planning before you begin to work. Haphazardly selected trim that is poorly installed is sure to look worse than no trim at all.
Select a trim style that matches the design and character of your home, or what you envision that look to be. In homes with 8-foot ceilings, trim in the 4" to 6" width range generally looks best. Before ordering stock, measure out the linear feet of trim that you need, and add at least 10% for waste. You’ll find the job goes easier if you list or sketch out where each piece of trim goes, the length of each piece, and the type of joints you’ll need to make.
Building supply centers can often order from a wider range of styles than they typically stock on their racks. Don’t exclude local millwork shops – while you can expect to pay more (though prices may only be marginally higher), they typically offer higher quality trim in unique styles.
There are only a few key joints used in trimwork – take the time to practice the joints you aren’t familiar with. Assemble the tools you’ll need before you begin the work.
Begin with the easiest trimwork (baseboards) before moving on to the more exacting work (crown moulding). Start in rooms that are less important: storage room, laundry room, basement, closets – where you can practice your technique and build confidence. And, if you begin to feel frustrated or tired, stop. There isn’t any prize for getting it all done in one fell swoop.
Material Choices
Solid Wood – There are four basic types of material to choose from. Solid wood is the traditional choice, the king of trim, and is priced accordingly. Because it is less dimensionally stable than other materials it needs to be more carefully installed.
Fibreboard – If you plan to paint the trim, then medium or high-density fibreboard (MDF, HDF) is a good choice, except in bathrooms, kitchens, and rooms subject to fluctuating moisture levels. It generates a lot more dust than solid wood, and it is more fragile to handle and install.
Finger-Jointed Solid – An alternative to MDF is finger- jointed trim. It is more impact resistant than MDF and typically comes in longer lengths. However, be careful when selecting stock as quality can vary considerably.
Composite – There are also composite trim materials. Polyurethane (particularly the ‘architectural grade’) is just as durable as MDF, but lighter in weight, and is well suited for curved installations. It comes in a wider range of styles and is easy to cut and install. Polyvinyl chloride (PVC) and vinyl are economy materials, and come in a more limited range of styles. PVC is less dimensionally stable than polyurethane, while vinyl tends to have a more institutional look. Polystyrene is superlight, making it the easiest trim to cut and install (with caulking), but it’s the least durable trim.
Remember, if using solid wood or finger-jointed boards, make sure you let the wood acclimatize for at least a week or so before using it. While composite materials shrink significantly less than solid wood, it’s still a good idea to let them breathe for a few days before installation.
Tool Up
Basic tools for the job include a hammer, tape measure, try or combination square, level, coping saw, chalk line, sand paper, caulking gun, nails and glue. For cutting trim, the best tool to use is a compound mitre saw. If trimming a single room you can always rent the saw. Otherwise you can use a table saw or a handsaw and mitre box.
I reinforce mitre joints on solid wood trim whenever possible. A biscuit joiner works well for this application. For installing the trim, you’ll find a brad or finish nailer makes the job go a whole lot quicker and easier. Otherwise, hand-nail the trim in place. You’ll also want to glue all the joints together, and after the trim is installed, caulk the seams between the trim and wall.
Four Joints You Need to Practice

The key to a professional look are clean, tight joints. The three most common joints you’ll find in trimwork are end mitres (for outside corners), face mitres, and coped joints (for inside corners). Mitres are relatively easy to make, particularly with a mitre saw. When joining multiple lengths of trim along long walls you’ll also cut scarf joints, which are mitre cuts made at 45°.

Yes, coped joints are somewhat more difficult to make (particularly in composite materials) but certainly not beyond the skill of the average DIYer. Typically, only one trim board needs to be coped – the other trim board rests flush against the wall. For this you’ll need a coping saw and patience. Practice on scrap stock before you begin your trim job. You can also cut the coped joint before cutting the piece of trim to length. If you make a mess of the coped joint you can simply cut an inch or so of material off and start over.
If trimwork is new to you, or if joinery was never your strength, grab a few pieces of wood and start practicing these joints. Using 3/4" - 1" thick stock works great, as it's at least as thick as most of the trim you will be using. It's generally easier to hide your mistakes when using thinner wood, so by using stock that's thicker than average your mistakes will be highlighted for you to see, and in turn learn from, before you start working on the real thing. Any practice you put into these joints will also pay off in your furniture making, as joint accuracy is also crucial then.
From Floor to Ceiling

Baseboards – The easiest trim to install starts at the bottom of the wall. Baseboards cover the gap between the flooring and the wall, and serve to protect the wall from damage. Visually, they serve to anchor the wall to the floor. The simplest install is just the baseboard. However, a more refined look includes a shoe, installed in front of the baseboard, and a cap, installed over top the baseboard. Composite baseboards sometimes incorporate all three elements into a single piece of trim.
Chair rail/Wainscot – While you can install a chair rail by itself, it’s often incorporated into wainscot. The chair rail, like the baseboard, protects the wall from damage (traditionally from chairs). It also visually breaks the tall expanse of walls. It can be particularly effective in homes with high ceilings.
Wainscot covers the section of wall from the baseboard to the chair rail. It can be installed for practical reasons (over damaged plaster or gyprock walls) or, more commonly, for its aesthetic appeal. The wainscot panels can be made of solid wood, cabinet grade plywood, beadboard, or composite materials.
Crown Moulding – Where baseboards anchor the floor to the wall, crown moulding anchors the wall to the ceiling. The curved profile of crown moulding takes away the abrupt, sharp angle where the ceiling and wall meet.
Installing crown moulding is more demanding than other trimwork, in part because you’re working on a ladder, over your head. Also, unlike baseboards, any inconsistencies in the moulding are much more apparent. And it can be awkward to install long sections of moulding, so having a helper is quite useful. Perhaps you’ve tackled the installation of other trimwork in your home, yet feel uncomfortable with the thought of doing the crown work. There’s no shame in hiring a contractor to finish the job for you.

Window Casings – The best time to replace window casings

is when you’re upgrading your windows. Fortunately, removing casings isn’t overly onerous. In some cases you can significantly enhance the appearance of a room by replacing the head and side casings, along with the apron, while retaining the head and side jams, and sill. Regardless, this is a more time-consuming job that is best taken on during mild weather and when you’re not pressed for time.


Door Casings – As with windows, you might think to

upgrade door casings only when replacing doors. However, if you’ll be installing new baseboard and crown moulding in a room, changing door casings can have a dramatic impact on the look of the room. And, as with window casings, it’s not overly difficult.

Built-up Moulding – In some instances, particularly in older homes, finding crown moulding to match existing ornate moulding can be difficult or costly. The solution may lay in creating matching moulding by building it up with off-the-shelf or shop-made mouldings. You can use this same approach to create your own unique trim for window and door casings. Sometimes specific looks can only be achieved by using this builtup approach. And as woodworkers we have the tools and skills to create the mouldings ourselves with basic tooling like routers, router tables and table saws. If you really want to get ornate you can add texture, or other small details, to the moulding to help differentiate it from store-bought trim.

If you’re looking for a way to really jazz up any room in your home, consider upgrading the trimwork. The key to success is pacing yourself, tackling one section at a time and making precisely cut joints. If you’ll be installing a fair amount of trim, consider investing in a compound mitre saw – it will make the job a lot easier and you’ll have a great power tool that will be highly useful for a lot of other woodworking projects.

Classic Wainscoting (Dec/Jan 2008)
Mitre Saws (Dec/Jan 2009)
Installing Crown Moulding – 3-Part Series (starts Oct/Nov 2009)

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