How To Build Frameless Base Cabinets

Free Frameless European style base cabinet plans that you can build for your kitchen, bathroom, office, home theater or other renovations. This is more than just how to build a base cabinet. It's practically everything you need to know about building frameless base cabinets before you begin. 

When I first tried to learn how to build cabinets I had a hard time finding all the information I needed. There was a little bit here, a little bit there, but nowhere did I find all the information all in one place. I did my best to combine most of what you need to know in one place to make things easier for you. It's a bit of a long read but if you're serious about building your own cabinets it to save money it's well worth the time. One book I commonly saw mentioned was Build Your Own Kitchen Cabinets (Popular Woodworking) by Danny Proulx which might be worth considering. I haven't read it myself.

If you'd like to help support the site you can purchase a printable PDF of this article for only $6.95.

Frameless cabinets are easy and affordable to build. They also provide more usable storage space over face frame cabinets. Over the years I've looked into different construction techniques for frameless cabinets and have put all that information together to help you build your own frameless base cabinets. To build matching wall cabinets see my post on How To Build Frameless Wall Cabinets. Construction of the base cabinet is relatively straight forward. The most difficult aspect is planning and sizing which will make up a good bit of this post.

Frameless cabinets have a more contemporary look but can be dressed up with trim and more elaborate doors to have a more traditional look.

In this article we're going to focus on how to build a frameless base cabinet carcass. The cabinet carcass is the main box of the cabinet which does not include doors, drawer fronts or drawer boxes. The cabinet carcass can be configured in a number of different ways to allow doors, drawers, open shelving or any combination which suits your needs.

The frameless cabinet design I find easiest to build, install and provides exceptional strength is the one pictured right. It is made of 3/4" plywood throughout, including a full back. The top consists of 2 4" stretchers. Up to a 30" wide standard base cabinet carcass can be constructed out of a single sheet of 4' x 8' plywood.

This is the design we'll focus on but I'll address some other options and aspects.

Cabinet Base Options

There are 4 different ways you can configure the base of your lower frameless cabinet. Each one has it's pros and cons.

Standard Base

The standard base has the sides and back of the cabinet extend all the way down to the floor and is notched in the front to provide a toe kick. The notch is 3" deep and 4-1/2" tall. There is a "sub toe kick" that provides additional support for the bottom and makes it easy to apply your finished toe kick cover (such as a decorative baseboard) over a continual stretch of cabinets for a seamless look.

This type of base is marginally more difficult to build and uses a little more plywood but you get a single cabinet unit which has advantages. Each cabinet needs to be shimmed individually to make it level. This is what most semi-custom cabinets you buy look like.

Standard Base No Toe Kick

Sometimes you won't need a toe kick at all such as when you're building a built-in desk or library. This base has the same pros and cons as the standard base except it has no toe kick. Instead a decorative board, the same thickness of the doors, is applied over the base of all cabinets after installation for a seamless look.

Adjustable Cabinet Legs

Adjustable cabinet legs (such as these Cabinet Leveling Legs or better Blum Leg Levelers and Blum Kick Plate Clips) make installation of cabinets very easy on uneven floors and let's face it, most floors have some degree of unevenness to them.

What's more, it's easy to make changes to the cabinet height during installation (and with a little more work after installation) if the need arises.

The toe kick board gets screwed onto a plate that clips onto the legs after all cabinets have been installed and leveled. Unlike the standard base, it's easy to add a toe kick on the side of a cabinet such as the exposed end of a cabinet run. It also makes it easier to change the toe kick board to change the look of your kitchen at a later date.

Since the wood cabinet is kept off the floor these are good for spaces where dampness is an issue such as in basements, garages or other areas where cabinets are installed on a concrete slab floor.

The downside is it will add a little bit extra to the cost of each cabinet but not much and the benefts will usually outweigh the cost.

Separate Base Platform

Finally you can create a separate base platform that consists of a frame made up of 2x4's with a plywood top giving you a total toe kick height of 4-1/4" (3-1/2" 2x4 + 3/4" plywood). What's nice about this arrangement is you level the platform before installing the cabinets. Then you just need to place your cabinets on the platform without having to do much if any additional leveling. The base is also sturdier than a base that is part of or attached to your cabinets.

You can even create toe kicks on the sides of cabinets where necessary such as the end of a cabinet run or a kitchen island.

Cabinet Back Options

You also have a few options on how you construct the back of the cabinet.

Full Back

You can choose to use a full back that is the same 3/4" plywood used for the rest of your cabinet. (Some people choose to use 1/2" but I find it's easier to just use one thickness throughout.) This configuration will give you an enclosed cabinet with exceptional strength which is important when installing heavy stone countertops and supporting heavy countertop appliances. It can be a little more money but not much if you plan your cuts out well. We'll be using the Full Back in the example in this article.

Nailer Back

Sometimes you don't care if a cabinet has a back or not, such as in garage storage cabinets. This option can save on material. Instead of having a full back you create 2 nailing strips out of 3/4" plywood for the top and bottom of the back so you have something to affix the cabinet to the wall with and to provide rigidity and strength to the cabinet.

1/4" Back With Nailers

In some cases you'll want to have an enclosed back but you want to save some money. You can use nailers as in the previous option but also staple a 1/4" plywood back over the nailers to provide a finished look. This is cheaper than using a full back and provides a lighter cabinet. Many semi-custom cabinet manufacturers use this technique. It doesn't add as much strength as a full back but it does give you the look and feel of one. The 1/4" plywood is more prone to warping than the 3/4" plywood and may bow out over time.

What You'll Need

Tools

• Table saw or circular saw and guide for making accurate and square cuts in plywood.
• Combination square
• Kreg Pocket Hole Jig
• Kreg Shelf Pin Drilling Jig

Materials

3/4" hardwood veneered plywood is the best option for building your cabinets. If you're taking the time to build your own cabinets might as well make them the best you can. You're still going to save money over most semi-custom cabinets that are usually made out of 5/8" particle board and wind up with a better quality cabinet. 

Plywood comes in different apperance grades. A1 being the best. If you plan on painting your cabinets or don't care about the apperance (garage cabinets) you can use a lower appearance grade cabinet. If you must use MDF to save money make sure you glue your joints in addition to using the appropriate pocket screws . 

Step 1: Calculate Cabinet and Component Dimensions

Chances are you will want to build a different sized cabinet than what I'm going to show in this example. In most cases you'll want to build multiple cabinets of different sizes so let's go over how to calculate the dimensions of the different components that make up the carcass. 

Cabinet Height

The height of the cabinet will be determined by the application. For example the standard height for the top of a kitchen work surface is 36". If our countertop thickness will be 1-1/2" that means our cabinet needs to be 36" - 1-1/2" or 34-1/2" tall.

Cabinet Height = Desired Top Height - Top Thickness

Some common work type heights are:

• Kitchen 36"
• Bathroom Vanity 33" to 36"
• Desk 30"

Cabinet Depth

The standard depth for kitchen cabinets is 24" which includes the door. This should work for most situations but you may want to check the specifications of your appliances (slide in range, dishwasher, etc) to see if they require a different size. 

For bathroom vanity cabinets the standard depth is 21". For desks and other custom cabinets you can choose whatever depth works best for you though most are 20-30" deep.

Cabinet Width

This one is easy. The cabinet width is determined by your design and your preferences.

Cabinet  Component Dimensions

In our example we're going to be constructing a 30" W x 34-1/2" H x 24" D cabinet using 3/4" plywood. We'll be making it with a standard base and a full back. In all the dimensions below the direction of the grain will follow the height.

*Note: if you're using thick edgebanding you'll need to factor that in where appropriate. Most edgebanding is less than 1/32" thick which is pretty insignificant so I don't factor it in most of the time. As long as it's used consistently and applied before assembly I consider it an acceptable margin of error. Wood expands and contracts. Not all human cuts are very accurate. Consistency is more important over precision and it makes calculating sizes and cutting components much easier.

Cabinet Side Dimensions

We will need two sides for the cabinet. The height of the side is simply the height of our cabinet minus an external base if using one. The width is the depth of the cabinet minus the thickness of the door.

Cabinet Side Height = Height of Cabinet - External Base (34-1/2" - 0 = 34-1/2")

Cabinet Side Width = Depth of Cabinet - Door Thickness (24" - 3/4" = 23-1/4")

We'll need 2 34-1/2" x 23-1/4" sides for our cabinet.

Cabinet Bottom Dimensions

The height for the bottom of our cabinet will need to be the width of our cabinet minus twice the thickness of the sides. The width will be the depth of the cabinet mins the back depth minus the door thickness. (Be careful sometimes advertised size isn't true size. A digital caliper can help you get an accurate thickness measurement. Your 3/4" plywood may sometimes be 23/32" or something else entirely.)

Cabinet Bottom Height = Cabinet Width - 2 x Side Thickness (30" - 2 x 3/4" = 28-1/2")

Cabinet Bottom Width = Cabinet Depth - Back Thickness - Door Thickness (24" - 3/4" - 3/4" = 22-1/2")

We'll need one back that is 28-1/2" x 22-1/2".

Cabinet Shelf Dimensions

If you're installing a shelf in your cabinet (as our example does) you want to size it appropriately. It's basically the same dimensions as the Bottom minus a little depth (1/2") so that it stays clear of the doors even if there is some expansion.

Cabinet Shelf Height = Cabinet Bottom Height (28-1/2")

Cabinet Shelf Width = Cabinet Bottom Width - 1/2" (22-1/2" - 1/2" = 22")

Cabinet Back Dimensions

We can use some of the previous dimensions we calculated to determine the dimensions of the back of the cabinet. The back of the cabinet will rarely be seen and even when it is it won't be lit very well. While it's nice to have a consistent grain direction for the backs you might be able to save a sheet of plywood by mixing the grain direction up for the backs if you don't mind a little inconsistency in an inconspicuous location.

Cabinet Back Height = Cabinet Bottom Height (28-1/2")

Cabinet Back Width = Cabinet Side Height - Stretcher Thickness (34-1/2" - 3/4" = 33-3/4")

Our cabinet needs one back measuring 28-1/2" x 33-3/4".

Stretcher and Sub Toe Kick Dimensions

Grain direction should be along the long side but in most cases these components will hardly be seen so feel free to change the orientation if it helps you maximize the usage on your cut plan. 

Stretchers should be 3-4" wide, the sub toe kick should match the height of the notch cut into the base (4-1/2" in our example). The height of both should be the same as the Cabinet Back Height (28-1/2").

We'll need 3 stretchers (4" x 28-1/2") and one sub toe kick (4-1/2" x 28-1/2")

Step 2: Attach Side To Back

Wow! You've read all this way and we're just starting to put the cabinet together! Careful planning makes the rest of the process easy.

Start by applying edgebanding to the front of both cabinet sides.

Drill pocket holes around the top and sides of the Cabinet Back and attach it to one of the sides as shown.

Notice that the bottom of the back is flush with the bottom of the side. There is a 3/4" space on the top of the back for the stretcher that will eventually be installed.

Step 3: Attach Bottom

Apply edgebanding to the front of the bottom, drill pocket screw holes as shown and attach the Bottom to the Side and Back previously assembled. Notice that the bottom of the Bottom is flush with the notch for the Toe Kick. Use your square to make sure everything is aligned properly.

Step 4: Attach Other Side

Attach the other side to the cabinet assembly using the previously drilled pocket holes in the Back and Bottom pieces.

Step 5: Attach Stretchers

Apply edgebanding to the front of the 2 stretchers that will be attached to the front. Drill pocket holes and attach to the cabinet making sure everything is square. The bottom stretcher on the front is for the first drawer. To minimize visibility of the pocket holes install them with the pocket holes facing up. (The drawer will hide the second front stretcher holes.)

In this example we're assuming the cabinet will have a single full width drawer and 2 lower doors. The spacing for this bottom section will be determined by the desired drawer height. The standard top drawer height is 6". We're planning for overlay drawers and doors. A 1/4" gap should be on the top to avoid any binding against the counter top. That means the second front stretcher should be 6-1/4" down from the top of the cabinet.

Step 6: Install Sub Toe Kick

The Sub Toe Kick helps support the cabinet and add rigidity. It also makes it easy to nail in the finished kick board after installation. Drill pocket screw holes and attach it between the cabinet sides as shown.

Step 7: Drill Shelf Pin Holes

Using the Kreg Shelf Pin Jig make holes in the back and front of each side of the cabinet for shelf pins. Leave at least 3-4" on the top and bottom for room to install your door hinges depending on where you drill the bores for your hinge cups on the door.

Use the short side of the jig without the fence to get the holes 37mm from the front edge of the jig. When doing the back, flip the jig around.

When you're done, apply edgebanding to the front of the shelf, insert shelf pins in the appropriate locations and install your shelf.

To learn how to make drawers see my post on How To Make Drawer Boxes. 

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How To Build Frameless Wall Cabinets

European style frameless upper cabinets are easy to build with the right tools, are affordable and are used for a variety of projects from kitchens, to bathrooms, offices and more. When I first tried to find information on how to build my own cabinets I found it a bit confusing. In case it helps others I'm going to go over what I've learned over the years. In this post you'll find information on frameless upper cabinet construction and instructions on how to build them.

These basic wall cabinets have a very clean, contemporary look but frameless cabinets are versatile. By using nicer doors, adding some crown molding and light rail trim you can achieve a more traditional look.

You can save a lot of money if you build your own frameless cabinets. While building frameless cabinets isn't very difficult it is important that the cuts are accurate and the pieces as well as the assembly is square. Before you go crazy in your kitchen with a sledgehammer and order a large pile of plywood Try to build one small cabinet to make sure you're happy with your results.

What You'll Need

Tools

• Table saw or circular saw and guide for making accurate and square cuts in plywood.
• Combination square
• Kreg Pocket Hole Jig
• Kreg Shelf Pin Drilling Jig
• Concealed Hinge Jig

Materials

You'll need 2 sides, one top, one bottom, one back, one or more shelves and one or more doors. 

Unlike my other posts, there is no cut list or cut plan because these are general instructions and the size of the cabinet will vary based on your needs. Instead I'll provide information on how to calculate the dimensions of the components you'll need to build your own cabinets to your specifications.

If you'd like to help support the site you can purchase a printable PDF of this article for only $6.95.

The type of material you choose will depend on where you will be installing the cabinets. In your kitchen you'll want to use nicer material than in your garage.

Material for Cabinet Carcasses

The cabinet box is also called the carcass. The thicker the material you use, the stronger the cabinet will be and the longer you can make your cabinets. 3/4" material is recommended but in some situations 5/8" or 1/2" can also work. Some woodworkers use different thicknesses for different parts of the carcass such as 1/4" backs inserted into a groove with 1/2" nailing strips, or 1/2" for the back and sides and 3/4" for the top and bottom. This is mainly done to save money. If you're only building a few cabinets for yourself you can simplify the process and wind up with stronger cabinets if you just use the same thickness material (3/4") for all the components.

Plywood is better than MDF is better than particle board. If you're using plywood it's important to note that plywood comes in different grades. One grade for the good side and one grade for the back side. A1 is the best appearance grade of plywood you can get. If you want to save some money you can choose to build the carcasses out of a lower appearance grade plywood such as B2 and use the A1 plywood for exposed ends and doors. Some even like to use melamine coated particle board for the carcasses with better plywood for doors and end panels. If you plan on painting your cabinets the grade of the plywood isn't as important. 

For shop cabinets in the basement or garage you might be able to find "shop grade" plywood at your local lumber mill. This plywood would have more defects in the veneer but still have a strong core. Many people even build shop cabinets out of CDX plywood. It's not very pretty but the X in the name indicates the glues used can handle a bit of exposure to weather which could be good in a garage.

If you're going through the trouble of building your own cabinets you're already saving a considerable amount of money and it makes sense to go with plywood in most instances. For the purpose of these instructions I'm going to assume the cabinet will be built with 3/4" plywood.

Material for Cabinet Doors

You can make plain slab doors out of the same material you use for your cabinet carcasses. In our case plywood. This will be the cheapest option and the one I'll be using in this guide because there are too many options and methods to construct cabinet doors to discuss here.

If you're not happy with a plain slab cabinet door a number of companies will make custom doors for you in a variety of styles at reasonable costs.

Step 1: Calculate Cabinet Component Dimensions

Before we begin cutting and assembling our cabinet we first need to determine what size cabinet we need. If you've ever gone to a kitchen showroom you've probably noticed that the semi-custom cabinets they offer come in some standard sizes. Since we're building our cabinets we can choose any custom dimensions we want to suit our needs. There are some limitations however. The material and thickness chosen will decide how wide a cabinet we can build. In most cases with 3/4" plywood about 42" should be the maximum width but narrower cabinets will have more stability.

Standard upper cabinet depth is 12" (including door) when over a counter. Deeper when over a refrigerator and has more support. The 12" upper cabinet depth leaves a 10-1/2" interior depth. Dinner plates are usually 10" in diameter but can up to 12". If you have larger plates, or want to leave room for larger plates in the future, make your cabinets deeper. In our tutorial we'll build a frameless upper cabinet that is 18" W x 30" H x 12-1/2" D. This will leave an 11" interior cabinet depth.

Our cabinet will be made up of 6 pieces of plywood. 2 Sides, a top and bottom, a back and a door. All will be cut from 3/4" plywood. To determine the size of each component we'll use the following formulas.

(For consistency the "height" is also the direction of the grain.)

Cabinet Side Dimensions

There are 2 sides and in most case the dimension runs vertically. The height of the side is the same as our desired cabinet height. Because we're using overlay* doors the width of the side is our desired cabinet depth minus the thickness of the door.  In our case we have:

Side height = 30" (height of cabinet)

Side width = 12-1/2" - 3/4" (depth of cabinet - width of door) = 11-3/4"

We'll need 2 11-3/4" x 30" pieces of 3/4" plywood.

(Overlay doors sit in front of the cabinet. Inset doors sit within the cabinet. For inset doors the width of the sides will be the same as the width of the cabinet.

Cabinet Top/Bottom Dimensions

The top and bottom pieces have the same dimensions. The width of the top/bottom is equal to the depth of the cabinet minus the thickness of the door. The height of the top/bottom is the width of the cabinet minus the thickness of each side.

Top/Bottom height = 18" (cab width) - 2 x 3/4" (side thickness) = 16-1/2"

Top/Bottom width = 12-1/2" (cab depth) - 3/4" (door thickness) = 11-3/4"

We'll need 2 16-1/2" x 11-3/4" pieces of 3/4" plywood.

Cabinet Back Dimensions

The back of our frameless cabinet fits in between both sides and the top and the bottom. To determine the width of the back we need to subtract the thickness of each side piece. To calculate the height we subtract the thickness of the top and bottom pieces.

Back height = 30" (cab height) - 3/4" (top thickness) - 3/4" (bottom thickness) = 28-1/2"

Back width = 18" (cab width) - 2 x 3/4" (side thickness) = 16-1/2"

We'll need 1 28-1/2" x 16-1/2" piece of 3/4" plywood.

Adjustable Shelves Dimensions

Depending on the height and purpose of the wall cabinet you may want to have one or more adjustable shelves. These are peices of 3/4" plywood that rest on shelf pins which are inserted in a series of shelf pin holes inside the cabinet.

The shelf is the width of the inside of the cabinet and extends from the back of the inside to 1/4 inch from the front.

Shelf height = 18" (cab width) - 2 x 3/4" (side thickness) = 16-1/2"

Shelf width = 12-1/2" (cab depth) - 3/4" (door) - 3/4" (back) - 1/4" (space) = 10-3/4"

Cabinet Door Dimensions

Our cabinet only has one door and we are designing the cabinets to be full-overlay. This means that the door sits in front of the cabinet and covers almost all of the cabinet. In reality the door needs a little bit of space around it to prevent it from rubbing against adjacent doors or walls. 

The minimum space with most hinges is 1/16" so we need to subtract 1/8" (2 x 1/8") from each dimension. That will also give us a nice 1/8" spacing between doors from other cabinets too. 

Door height = 30" (cab height) - 1/8" = 29-7/8"

Door width = 18" (cab width) - 1/8" = 17-7/8"

If we were building a wider cabinet that required 2 doors we would still subtract 1/8" for the height but the width of each door would be (CabWidth - 1/4")/2. There would be a 1/8" space between the two doors and 1/16" space around the perimeter.

Now that we know what size pieces of plywood we need we can begin assembly.

Step 2: Assemble Sides, Top and Bottom

Should you use glue? Pocket hole joinery is pretty strong but glueing the joints in addition to screwing will give you a stronger more rigid cabinet. If you do decide to use glue, first assemble the cabinet without glue to make sure everything fits and lines up well. Then disassemble and reassemble with glue.

Edgebanding: Apply edgebanding to the edge of each of the 4 pieces that will be on the front of the cabinet.

Start by drilling pocket holes in the Top and Bottom pieces as shown and attach the Top to one of the side pieces.

Now attach the bottom to the side. Make sure the pocket holes are on the outside of the cabinet.

Attach the last remaining side, making sure everything is aligned properly and square.

Step 3: Cabinet Back

Double check to make sure the back of the cabinet is square and make sure it fits inside the back of the cabinet. If not, make adjustments to the back.

If everything fits together properly, is the right size and is square, disassemble the cabinet and repeat Step 2 above, this time with glue before inserting the back.

Drill pocket hole screws around the perimeter of the back and attach it to the rest of the cabinet as shown using glue.

Because we're using pocket screws we've built this entire cabinet without a single clamp. Normally a lot of long, expensive bar clamps are used when building cabinets or other furniture to keep the cabinet in place while the glue dries. One of the benefits of using pocket hole joinery is the screws act like clamps to hold everything together while the glue dries.

Step 4: Drill Shelf Pin Holes

Remove the fences from your Kreg Shelf Pin Jig and place it at the bottom of the cabinet as shown. The short side should be flush with the front of the cabinet. This will position the holes 37mm away from the front.

Use the second and third holes from the bottom to drill pilot holes for the hinge mounting plate.

Slide the shelf pin jig up to the top of the cabinet, keeping it flush with the front of the cabinet and drill holes for the top hinge mounting plate in the 2nd and 3rd holes from the top as shown. 

Now place the indexing pin in the bottom hole of the jig, slide the jig down to insert the indexing pin in the 1st Shelf Pin Hole drilled previously and continue your way up the side of the cabinet drilling shelf pin holes. Stop before you get to the pilot holes for the top hinge mounting plate.

Flip the shelf pin jig around and place it in the back corner of the cabinet so the short end of the jig is closest to the back as shown. Drill the 1st shelf pin hole in the last hole from the bottom. (We don't need pilot holes for the hinge in the back.)Then continue drilling the remaining shelf pin holes along the back using the indexing pin.

Repeat this step on the other side of the cabinet.

Step 5: Mark Hinge Bore Locations

On the back, hinge side of the door, mark 2 lines 3-3/16" from the top and bottom of the door. This is the center-line for the hinge bore.

Follow the instructions that came with your hinge boring jig (such as the Concealed Hinge Jig) to drill the 35mm bores for the cup end of the hinge. 

Finally attach and adjust your hinges so the door has an even overlay all the way around the cabinet.

Insert some shelf pins, and your shelf and the cabinet is done. Paint and prime, or stain and finish.

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Better Box Fan Air Purifier

A better more efficient and odor eliminating homemade air purifier than just taping a 20x20x1 filter to a box fan. Sometimes you need to help clear the air in a dirty environment but don't want to use an expensive air purifier such as in a room after renovating and painting. Here's a cheap and easy way to build one.

Air purifiers can be expensive and you've probably seen articles recommending to just put a 20" x 20" x 1" furnace filter on a cheap 20" box fan and POOF! instant cleaner air for not a lot of money. It really does clean the air pretty cheap.

There's a problem with this though. These fans weren't designed to be run with a filter. The filter will restrict air flow which will put a higher strain on the motor causing it to use more electricity and in worse cases could be a fire hazard. The higher the MERV rating (cleaning efficiency) of the filter the more stress it will put on the fan.

Don't worry! You can still have your cheap air purifier as long as the filter area is increased to decrease the effect of air resistance. Instead of using one 20x20x1 filter we'll use two 20x25x1 filters which increases the filter surface area over 250%. It's a little more expensive because you're using two filters instead of one but the increased filter surface area also helps the filter last longer before it gets clogged up and we're saving on energy use compared to a single filter.

I can't take credit for the design, I found it via Marshall Hansen Design but I'm using different filters.

I recently remodeled my basement and there's a lot of dust (including drywall dust and sawdust) and fumes from paint, cleaners and other building materials. It's an underground basement and mold has to always be a conern too. Because part of the space will be my home theater in the future I plan to get a more expensive air purifier that's smaller and quieter such as this Fellowes Quiet Air Purifier AP-300PH with True HEPA Filter because it has great reviews, is reasonably priced and the replacement filters aren't that expensive or a Sharp Plasmacluster True HEPA Air Purifier or Blueair HepaSilent Air-Purification System if I find some extra Benjamins in the couch cushions. But I don't want to put that in the dusty environment right away because I'll have to replace the more expensive filters fairly quickly because the air is so bad. I also don't want to spend the money right now but I do want cleaner air now.

So I decided to get things going with a homemade air purifier that has filters that not only clean the air of particulates but also reduce VOCs and odors. Even after I purchase an air purifier I'll still have an air purifier I can use for other purposes like when I'm painting or cutting wood.

Also, don't forget to add more plants to your home. They're natures air purifiers. Not only do they convert carbon dioxide to oxygen but houseplants filter toxins and emit negative ions too!

What You'll Need

Materials

• Filtrete Home Odor Reduction Filter, 20-Inch by 25-Inch by 1-Inch, 4-Pack (only using 2 at a time)
• 20" Box Fan
• Cardboard (from the package the filters came in) or oak tag
• Duct Tape or Clear Cellophane Tape
• Optional  Plug-in Timer so the fan isn't running constantly without manual intervention.

Tools

• A pair of scissors or utility knife

Quick Info About Filters

The nice thing about this box fan filter setup is you can use any filters you want. If you are only concerned about large particles generated from something like cutting wood, you can use cheaper, lower MERV rated filters. If you're worried about finer particles from allergens such as mold, you can use a higher MERV rated filter. To understand more about what the MERV ratings mean have a look at Table 2 on this EPA article on residential air.

I chose to go with the Filtrete Home Odor Reduction Filters which are a new type of filter from Filtrete. They contain a lot of activated carbon to help filter out odors and VOCs.  They are rated MERV 11 and are equivalent to their 1000 MPR furnace filters. They should do a good job with even the fine drywall dust and the activated carbon will help a lot with odors. I bought a 4 pack for around $57 which gives me 2 sets of filters.

Filtrete Odor Reducing Air Filters

The filtering power of these Filtrete Odor Reducing filters isn't listed on Filtrete's website or on Amazon but I contacted them and found out that these filters have a MERV 11 rating and filter 90% of particles between 1-10 microns which makes them more efficient than the Filtrete Micro Allergen Reduction Filters I've been using in my air conditioning for the past few years. Plus Filtrete packs over 180 grams of activated carbon to help reduce odors.

After I go through both sets of carbon filters I'm probably going to switch to the Filtrete Elite Allergen Reduction Filter which does a much better job of filtering small particles. If odors are a problem I'll get some Cut-to-fit Carbon Prefilters and tape them over top of the Filtrete filters.

Okay, enough of the why, now for the how!

Step 1: Unbox The Filters

You're thinking "OMG! He's actually describing how to open a cardboard box?!?!?!" The best deal I found for these filters were on Amazon and with my Prime membership (or supersaver shipping) the shipping is free. Plus the packing box is going to be part of the filter so we need to keep in intact.

The box is sealed very well. Not only is it taped but the seams are also glued together. To get the filters out of the box I cut the top where it's perforated with a utility knife as shown.

Be careful not to cut too deep and damage the filters. Keep the box someplace safe to the side while we continue. 

Step 2: Hinge Filters

Start by taking 2 of the filters out of their plastic wrappers and lay them one on top of the other with the air flow arrows pointing towards each other. With the Odor Reducing Fitlers this means the black, carbon sides will be facing each other.

With the filters lined up, tape one of the short (20") edges of the filters to create a hinge between the two filters as shown.

I decided to go with white duck tape so it looks a little nicer but it makes it hard to see in the photos against the white cardboard filter frame.

Step 3: Tape Filters To Fan

Lay the box fan face down on a flat surface to mount the filters to the back making sure the bottom of the filters are about flush with the bottom of the fan and do not extend past the bottom.

Use a strip of duck tape to secure each side to the side of the fan.

Step 4: Cut and Attach the Cardboard

Cut out one of the large sides of from the cardboard shipping box, place it over the top of the of the filters and secure it with a strip of tape to the top of the fan. Position it so that it's pretty even over both filters but it doesn't have to be perfect.

Using a pencil, trace around the filters (while pressing down the cardboard so nothing moves) to mark where the cardboard needs to be cut.

Lift the cardboard up (the front piece of tape acts like a hinge) and cut along the lines to trim the sides. By the way, I really like these Fiskars Cuts+More 5-in-1 Multi-Purpose Scissors.

Repeat the process for the bottom cardboard. The other large piece from the box is seamed but it's taped and glued and very stiff so it shouldn't be an issue but you can run a strip of duck tape over the seem if it makes you feel better.

Also keep in mind that the bottom of the fan has feet. I positioned the cardboard underneath the feet and then pulled the feet out to tape.

After taping up the sides of the bottom cover to the filters, I added an extra strip of duck tape all the way around where the filters/cardboard meets the fan for added support. The rounded corners of the fan means there might still be an air gap there so check them and add extra duck tape if necessary. On the bottom there are also some holes, duck tape over those as well. Finally, replace the feet.

Step 5: Seal The Back

Where the hinged filters meet the cardboard in the back, add another strip of duck tape for support and to seal any gaps.

Give another look around the seams to make sure there aren't any gaps. If you find any, tape them up.

When using the fan, I always make sure that the cord isn't underneath the cardboard and instead is under the metal fan chassis, just in case something goes wrong and the cord overheats. Can never be too safe.

Replacing Filters

When it's time to replace filters, use a utility knife to cut the filters free but leave the cardboard in place. Then just hinge and attach the new filters. 

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