This post is an overview of interior and exterior door types, what they are made of and the potential offgassing of VOCs of each type. We will look at which types are non-toxic and safe, with zero to little offgassing, and which ones contain toxic substances.
The post will focus on outlining the types of doors you will find at big box stores like Home Depot, specialty stores, and online. We will also cover unusual and creative options (including non-wood options) that will suit the most chemically sensitive or the true purist who wants the healthiest door possible.
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Solid Wood Doors
This category of doors are real solid wood through and through. Only really old doors might be one solid piece (a slab).
Modern solid doors are made from a number of solid pieces glued together in a frame and panel construction.
You might also find flush (flat) doors that have solid wood pieces inside and a veneer on the outside. When looking at a door that has solid strips glued together on the interior, you may want to know the size of the pieces of wood. Some companies may call this “engineered” if the solid wood pieces are as small as 1 inch each. This also, of course, means more glue used in the door.
Wood glues tend to be quite non-toxic and low to 0-VOC once dry, but you should get a sample if you have reactions to chemicals. I have seen epoxy used as well as wood glue and exterior wood glue.
When testing an epoxy be sure to test both parts mixed in a real-life situation to see how it comes out.
Also, look and what paints or stains are used. This door type can be used for interior and exterior doors. With exterior doors usually coming with a stronger stain or paint.
Accoya wood doors are a good option for exterior glass and wood doors. Accoya is a type of wood process where the wood is treated with acetylation to be naturally rot-resistant without adding toxins.
They also claim better dimensional stability and less shrinking and warping from moisture than untreated wood. Check their websites to find the companies that work with this wood and their distributors. These doors are pricey.
Solid wood doors are one of the most non-toxic types. You can find solid wood doors on Amazon, you may find a limited selection at big box stores, and many more options at specialty door stores and though custom builders.
Simpler Versions of doors made only with real solid wood:
Louvered doors can be used when not much privacy is needed. The ones I have seen are made out of just solid wood.
You can find them in unfinished and finish them yourself if you like.
Here is my list of non-toxic finishes and paints.
You can find these on Amazon and at big box stores.
Solid wood barn door can be found at big box stores like Home Depot as well as on Amazon.
You could also make your own solid wood door in this style out of the wood of your choice which would give you more control of the process and the wood itself.
Add hardware from Amazon.
Hollow Core Doors
Typical interior doors in new houses and apartments are hollow core. You can easily tell as they do seem to be hollow inside and are light.
The interior frames of these doors are solid wood or, more likely, composite like MDF.
To stabilize the hollow interior there may be a honeycomb interior (cardboard, plastic or hardboard) and there might be some solid wood in a strip down the middle.
The outer veneer surface can be real wood in non painted options, but usually, it is HDF/hardboard.
They usually come primed.
Hollow doors could have MDF or other pressed wood products along the frame.
These are interior doors.
What do Hollow Core Doors Like Masonite Offgas?
MDF (in the framing) is made with formaldehyde, there is a fair amount of glue here.
Hardboard/HDF/fiberboards (the door skin) could be made with either phenol-formaldehyde (which offgasses fairly quickly), asphalt or no adhesive, depending on type. Paraffin wax and or linseed can be added.
Masonite brand door:
Masonite doors are the most common door brand of interior hollow core doors. Many want to know if Masonite doors are non-toxic.
Masonite fiberboard skins are not made with an adhesive and are formaldehyde-free, but they do have other additives that are undisclosed (according to the SDS they sent me).
Masonite brand hollow core doors can be made with solid wood framing (which would make those ones non-toxic), but it looks like most of them have at least some composite framing of MDF (which offgasses formaldehyde).
Therefore it’s possible for this door type to have very little offgassing and to be formaldehyde-free if they don’t have MDF and if made with a fiberboard that does not use an adhesive.
Are hollow core doors safe for the chemically sensitive:
Some folks who are avoiding toxins or are chemically sensitive do choose to use this door type. Some do seal it with an AFM sealer or shellac before installing them to seal in some of the offgassing.
See the post on sealers for more info on sealing in offgassing.
Hollow core doors are easy to find at any hardware store and are inexpensive.
Solid Core Doors
Solid core doors have an engineered or composite wood inside, usually a fiberboard.
The outer skin is usually HDF/hardboard.
The other type of solid door is a solid MDF (or another composite wood product molded into a shape and painted).
These are usually interior doors.
This is my least favorite category of doors for those avoiding toxins or for chemically sensitive persons.
Because the core is a solid MDF (or other lower-density fiberboard) this potentially has the highest offgassing of the door types. MDF is made with formaldehyde, they offgas for quite a while.
You can find solid core doors on Amazon, at hardware stores as well as at specialty door stores.
Glass barn doors, in clear or frosted
Glass barn doors can be found in clear or frosted and can offer some privacy. The benefit is how little there is to offgas.
Glass and metal are inert. In some instances (or for the most sensitive), you may want to wash factory oils off the metal parts. But if you don’t pick up any chemical odors or reactions there, you may just skip that step. Those that need to go the most extreme, would also want to know what kind of finish in on the metal.
Glass and metal barn door. This style might be easier to find than the all-glass at the big box stores. Both types can be found on Amazon.
Frameless all-glass doors are more commonly seen in office buildings, at least in North America, but they can be seen in very modern houses all over the world.
You may find them at high-end residential companies or you may have to look at office supply companies. Frameless glass doors are all glass (other than the door handle, or the base tracks if it’s a sliding door), and are the safest, purist, least toxic door option.
Mirror closet doors can be safe and non-toxic (but check the backing). You can find these at big box hardware stores.
Solid wood and glass doors. I saw these doors pictured left at a B&B. The doors are framed in real solid wood with glass from a local company in Canada, called Wescon that specializes in doors (both custom and premade).
These are “seconds” so they were a good deal. This is a good example of a local specialty door company. They make solid wood exterior and interior doors, some with veneers. Some do have MDF, but you could avoid that style.
Metal doors are usually intended to be exterior doors. Steel doors are made of heavy-gauge galvanized steel over a core of rigid foam or spray foam (usually with wood framing inside).
They might be coated with a polymer or vinyl that could look like wood or have face veneers, or they can be just painted.
Apartment doors are typically steel in a simple slab construction pictured (the one pictured is by Jeld Wen and is simple steel with paint).
Flush exterior doors often have a core of solid foam (I have seen polystyrene and polyiso). I have seen polyurethane as well. Some have a honeycomb pattern inside as well as steel reinforced.
What’s inside a steel door is well sealed up by the metal (especially if the edges are welded) and so the offgassing should not affect the occupant.
You just want to look at the finish on the outside to make sure that is low-VOC and safe for you. The standard paint on a simple metal door is a primed paint that is baked on and is low-VOC. A simple painted metal door is preferable from a health standpoint to anything faced with vinyl or other polymer.
Masonite metal doors are for residential use (not commercial and apartments) – they have wood framing (real, laminated or composite), some doors have steel framing inside, polyurethane or EPS foam inside and galvanized steel on the exterior (painted).
I have seen folks find used metal doors at used building supply stores. Many supersensitive folks do use metal door intended for the exterior as interior doors, such as the Masonite brand. You can find these at hardware stores and specialty door stores.
If you want to use an exterior metal door (like this wood grain look from Home Depot) as an interior door, make sure to build wider framing than usual for the door frames.
Fiberglass doors are also exterior doors. They have a core of rigid insulation, or polyurethane spray foam inside, and are clad with a fiberglass skin, they usually have a wood look.
Inside the door may be wood (real and or composite) and plastic to frame it. The fiberglass skin is rather thin, but fiberglass is not typically a tolerable material for those avoiding toxic chemicals due to the offgassing.
Though you may find some brands preferable to others, or you may do well with a used one. I prefer metal doors to fiberglass in almost every situation in terms of toxicity and offgassing.
Patio door, sliding glass doors and other glass door types have framing in vinyl, fiberglass or aluminum. Similar to my assessment in my post on windows, I prefer metal. You still have to check for the coating or paint on the metal.
Hard vinyl can be quite tolerable for some, and some brands of fiberglass can be as well. Folks who are sensitive to chemical offgassing and toxins should check out both types, in different brands, if you cannot find metal framed patio doors.
Vinyl can also be used as a skin over metal doors which would not be a preference for me for healthy doors.
Almost any type of door including, flush, panel, louvered, and glazed, can be mounted as a pocket door. Just make sure the hardware is rated to handle the size and weight.
Corinne Segura is a Building Biologist with 8 years of experience helping others create healthy homes.
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