Foam backer board, also known as foam core board or foam board, is a versatile building material with many applications for both interior and exterior projects. It consists of a foam plastic core laminated between two facer sheets, typically composed of paper or fiberglass mat. Let’s take a closer look at what foam backer board is and the many uses it has around the home and job site.
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What is Foam Backer Board Made Of?
The core of foam backer board is made from polystyrene or polyisocyanurate foam. These are rigid, lightweight plastic foams. Common brands of foam board use extruded polystyrene (XPS) or expanded polystyrene (EPS). Polyisocyanurate may also be referred to as polyiso or PIR.
Here are some key properties of the foam core:
- Extremely lightweight – Much lighter than plywood or cement backer board
- Insulating – Foam has a high R-value for thermal insulation
- Water resistant – Does not easily absorb or transmit moisture
- Dimensionally stable – Doesn’t expand or contract with changes in temperature or humidity
- Easy to cut and shape – Can be scored and snapped by hand
- Compressive strength – Capable of bearing moderate loads
The facer sheets laminated to each side of the foam provide protection and a smooth surface for finishing. Here are the typical facer options:
- Paper – Multi-ply paper provide a smooth, paintable surface. A common choice for indoor use.
- Fiberglass mat – A coated glass fiber mat offers increased moisture resistance. Used for exterior applications.
- Aluminum foil – Reflective foil facers add a radiant barrier for energy-efficiency.
- Coated mineral board – Cementitious surface for use as a tile backer.
Types of Foam Backer Board
Foam backer board comes in several specialized varieties and thicknesses for different needs:
- Standard white foam board – With paper facers, comes in 1/4″ to 1″ thickness.
- Fanfold insulation board – Thinner panels scored for easy folding.
- Extruded polystyrene (XPS) – A strong, moisture-resistant foam for exterior use.
- Polyisocyanurate (PIR) – Features even higher insulating value than XPS.
- Foil-faced – Reflects radiant heat with aluminum foil facers.
- Cement board – With cementitious coatings for tile backing.
- Structural foam sheathing – Reinforced foam for structural strength.
- Stucco board – Has facers to accept stucco finishes.
The thickness, facer material, and composition are tailored to suit the specific application. Let’s look now at some of the common uses of foam backer board around the home.
Uses for Foam Backer Board
Wall Sheathing
One of the most popular uses for rigid foam board is as exterior wall sheathing. It is applied to the outside of the wall studs prior to siding installation. The foam provides a thermal break to prevent heat transfer through the wall. It also allows moisture to drain down the wall without absorbing into the framing. Foam sheathing is quick to install and achieves very high R-values with minimal thickness.
Under Siding
Foam backer board can also be installed directly beneath various siding materials. It creates a perfectly flat, stable surface for the siding to be attached to. Vinyl, aluminum, and fiber cement sidings will all benefit from a foam underlayment. The foam also improves insulation at this critical junction between the wall and siding.
Interior Wall Sheathing
Using foam board when framing interior partitions adds insulation and stability. This is helpful when dividing conditioned spaces from unconditioned areas like garages or attics. Foam-backed drywall delivers higher R-values than fiberglass batts alone. The foam boards also stiffen the wall and reduce sound transmission.
Basement Walls
Applying foam insulation directly to concrete basement walls is an easy way to improve energy efficiency. The foam acts as a vapor barrier, thermal break, and protective buffer between the wall and other finishes. XPS foam board is a common choice for basement wall insulation.
Under Drywall
Foam backer board can be applied behind drywall on both walls and ceilings. This boosts insulation while creating a very smooth and stable substrate. Typical foam thicknesses are 1/4″ to 3/4″ under drywall. Fire-rated foam boards are available when required.
Under Wood Paneling
Wood paneling often requires a very flat, defect-free surface to install against. Foam backer board provides the smooth, stable backing needed. Glue is applied directly to the foam before placing the tongue-and-groove panels over top. The insulation value of the foam also prevents condensation issues.
Tile Backer Board
Special cement-faced foam boards are designed specifically for tile installations. Being impervious to moisture, foam provides a waterproof underlayment for tub and shower surrounds. The cement coating allows thinset mortar to adhere when setting the tiles. Foam cement board is lighter and easier to cut than alternatives like cement backer board.
Tub & Shower Walls
Waterproof foam backer board makes an excellent substrate for tub and shower walls prior to adding the finish surface. Tile, fiberglass surrounds, or molded acrylic panels will all attach easily over foam. The foam board resists moisture damage and provides insulation to prevent condensation on cold surfaces.
Floor Underlayment
Foam board can be used beneath finished flooring to improve insulation and smoothness. Laminate and engineered wood floors should not be installed directly over foam. But foam underlayments are placed beneath the flooring substrate. Foam levels out small irregularities and provides cushioning.
Attic Floors
One of the best places to add more insulation in a home is under the attic floor. Foam boards are simple to install between joists. They prevent heat loss through the ceiling below. Use high R-value rigid foam designed for covered use.
Specialty Wall Panels
With their lightweight and easily worked composition, foam backer boards are ideal for creating specialty wall features:
- 3D wall panels – decorative or faux finishes
- Accent walls – focal walls and displays
- Division walls – screen or divide larger spaces
- Presentation boards – for school projects, hobbies, etc.
Almost any flat panel shape can be cut from foam board stock. The panels can be attached to walls or framed and hanged as standalone fixtures.
Craft Projects
For hobbyists, foam is a craft-friendly material for building miniature structures, decor objects, holiday decorations, children’s projects, and imaginative creations. The white paper-faced boards are easy to cut, shape, glue, and paint in any style.
Outdoor Signs
Durable foam boards with weather-resistant facers work great for custom outdoor signage. These could include business signs, real estate signs, event announcements, campaign signs, and wayfinding signage. Painted graphics and text will adhere reliably to foam for the long term.
Exterior Trims
Lightweight foam trim pieces can be used for exterior decoration and detailing. Foam holds up to weather exposure while offering very low maintenance. Trims pieces might include cornices, shutters,door surrounds, window trims, and decorative moldings. They are quick to cut, shape, and install.
Benefits of Using Foam Backer Board
Let’s summarize the many great qualities that make foam backer board such a versatile building material:
- Lightweight for easy handling
- Easy to cut, shape, and install
- Insulating to save energy
- Moisture resistant
- Provides stable backing surface
- Thin boards achieve high R-values
- Closed-cell foams do not harbor mold or bacteria
- Low maintenance for longevity
- Cost effective
Foam backer and sheathing boards deliver this exceptional combination of performance advantages unmatched by many other building materials.
Choosing the Right Foam Backer Board
With all the options available, it helps to understand how to select the right foam backer board product for your particular project:
- Consider interior vs. exterior use – Interior boards have paper facers, exterior boards fiberglass facers.
- Look for proper fire ratings – Use fire-rated foam where required by code.
- Determine needed R-value – Higher R-values provide greater insulation.
- Assess required rigidity – Rigid foams hold shape better under load.
- Check expected moisture exposure – XPS and PIR boards resist moisture best.
- Review thickness – Thicker boards are stronger and may have higher R-value.
- Verify surfaces are compatible with finishes – Cement board for tile, smooth paper for paint, etc.
Consult manufacturer technical docs for specific board properties. Their experts can guide you in selecting the optimal product.
Working With Foam Backer Boards
Foam backer boards are designed to be easy to handle and install. Here are some tips:
- Cutting – Use a sharp utility knife with frequent blade changes. Boards can also be sawn.
- Shaping – Hot wires provide clean cuts for curves and custom shapes.
- Fastening – Most boards attach with panel adhesives or screws. Some can be friction-fit.
- Sealing – Use minimal expansion joints and sealants at board joints.
- Finishing – Paint products are available for most facer surfaces. Follow mfr instructions.
- Safety – Follow safe handling practices and ventilate cut foam dust.
With practice, foam backer boards can be fabricated into just about any size and shape. Complex assemblies can be created.
Cost of Foam Backer Board
Foam backer board offers an economical solution for many construction and finishing needs. Costs vary by type and size, but foam boards are very competitively priced with other products.
Here are typical price ranges for common foam backer board products:
| Foam Board Type | Cost per SqFt* |
|---|---|
| 1/4″ EPS White Foam Board | $0.20 – $0.40 |
| 1/2″ XPS Insulation Board | $0.30 – $0.75 |
| 1/2″ PIR Foam Sheathing | $0.90 – $1.25 |
| 1/4″ Cement Backerboard | $0.35 – $0.55 |
*Prices above are sample ranges only. Actual costs vary regionally and by distributor.
For many foam board products, greater thickness yields greater R-value (insulation) at a very cost-effective rate. This makes foam backer boards a high-value building material.
Conclusion
With their unique blend of performance, ease of use, and affordability, foam backer boards are truly one of the most versatile building materials available. From wall sheathing to craft projects, foam board can provide the perfect backing for practically any application.
Understanding the different types of foam backer board and their specialized properties allows you to select the optimal product for your particular needs. Foam boards are lightweight, simple to install, and deliver substantial energy savings – qualities that make them a go-to material for builders, renovators, and makers alike.
So next time you start a construction project or hobby build requiring a reliable flat substrate, turn to trusty foam backer board. It’s sure to be the right backing board for the job.