Liquid Nails vs Wood Glue

Adhesives are critical to both woodworking and carpentry. While other means of fastening wood together and wood to various materials exist, adhesives are the “go-to” in countless cases, even when used with other forms of joining materials, such as fasteners. Understanding the different types of adhesives available is an essential part of any woodworker or carpenter’s tool kit.

One hears several different names when talking about adhesives used for wood. To the uninitiated, these may all seem to be more or less the same when, in reality, they are pretty different. Each is designed for a specific purpose and doesn’t work correctly when used outside the bounds of that purpose. While there is some leeway, it is limited.

The two most commonly heard names of these various adhesives are “Liquid nails” and “wood glue.” When talking about Liquid nails, we’re referring to a whole family of specially formulated construction adhesives created for different purposes and generally sold in caulking tubes for easy application over large areas.

Likewise, the term wood glue can mean several various types of adhesives, although this is not a brand name. Anything used to hold wood to wood is called “wood glue,” but the term is most often used to describe PVA adhesive (polyvinyl acetate). This is sold in bottles of various sizes.

Other than referring to adhesives used with wood, construction adhesive (Liquid nails) and wood glue (PVA) have little else in common. The question then becomes, which one is more applicable to the project?

By and large, that question can be answered by looking at the type of project being built. I know no instance where construction adhesives are used in the woodworking shop. This adhesive is too thick to be used in most types of woodworking joinery, where properly shaped parts fit snugly together without a gap. Gaps are a normal part of construction, and construction adhesives must be formulated to bridge those gaps and bond diverse materials together, even when they don’t fit snugly up against each other. While wood glue might be found on a construction site, it is pretty much only used for cabinetry construction.

PVA wood glue has little to no gap-filling capability. It works by soaking into the wood’s pores, forming a permanent mechanical bond with the wood. The thin layer of glue between the two wood pieces acts merely as a bridge between that which has soaked into the pores on one piece of wood and that which has soaked into the other. When woodworkers need glue with gap-filling capability, they switch to epoxy, which has a higher solid content and tensile strength to bridge the gap, providing a strong bond. The only time PVA is used with a gap is purely cosmetic when sawdust is mixed into it to form a paste-like filler that matches the color of the wood.

Another time when epoxy might be used for woodworking is with difficult woods. Some woods, such as cocobolo, rosewood, and purpleheart, are oily and resist adhesive. In those cases, the oils need to be cleaned off the surface of the wood, either with mineral spirits, acetone, or alcohol. It can also be helpful to sand the surface with medium grit sandpaper to provide the glue with a rougher textured surface to bond to. Finally, if the PVA glue doesn’t work, epoxy is the choice.

Construction adhesive, on the other hand, does not soak into the wood or any of the other materials it is used with but rather bonds with the surface. Its strength is in the bond that it forms and the tensile strength of the glue itself when fully cured.

Of the two, construction adhesive is more vital, although wood glue is still more potent than the wood that it bonds with, making the joint in the wood generally more substantial than the wood itself. Even in the end grain, considered the weakest glue joint in wood, it is typical for the wood fibers to separate before separating from the glue. Standard PVA wood glue has an average strength of 3000 PSI, while the different formulations of Liquid nails have tensile strengths of 3,600 to 4,000 PSI.

While construction adhesive can be used to bond wood to wood, such as in making headers and beams, it is most often used for attaching other materials to a home’s wood framing. Liquid nail brand adhesives can bond aluminum, wood, steel, stone, drywall concrete, brick veneer, Styrofoam insulation, and other materials. Because it does not depend on soaking into the material’s pores, it can be used effectively with both porous and non-porous materials and rough surfaces, such as stone and concrete.

Both wood glue and Liquid nails can be used for indoor and outdoor applications, but in both cases, it is necessary to buy the formulation designed for exterior use. Titebond III wood glue is an exterior formulation, as is Liquid Nails Outdoor Repair adhesive. The interior formulation of either type of adhesive may work outdoors for a while, but they are not waterproof and so will eventually be damaged by water and fail.

Another critical difference between the two is their working time and cure time. Wood glue has a five- to fifteen-minute working time, depending on the temperature and humidity. When correctly clamped, it will dry within 60 minutes. Once dry, the glue requires 24 hours to cure fully. On the other hand, construction adhesives need 24 hours to dry and will not fully cure, reaching their full strength in another six days.

Both types of adhesives need to be clamped while drying and curing, although this is often done in different ways. Projects built with wood glue are usually clamped with various clamps found in the workshop without using any fasteners.

However, fasteners can be used in conjunction with it, and often, the appearance of those fasteners will either be hidden or will not detract from the appearance of the finished project. Cabinetry, for example, is usually glued and nailed with wire brads, which leave only a tiny hole that can be quickly filled. But those brands are not used in fine furniture.

Clamping of construction adhesives is almost always accomplished with fasteners, either nails or some variant of drywall screw. The added benefit of using fasteners with either of these adhesives is that the fasteners add strength to the joint, explicitly helping it withstand shear and pulling.

While these are the main differences between these two adhesives, from the working point of view, some other differences may affect the choice. These are listed in the chart below:

Characteristic	Liquid Nails	Wood Glue
Dry Time	15 minutes	15 to 60 minutes
Cure Time	7 days	24 hours
Strength (fully cured)	3,600 to 4,000 PSI	3,000 PSI
Shelf Life	Two years	One year
VOC Level	It can require following of safety protocols	Little to none
Safety	Low to high, depending on the formulation	It can require following safety protocols
Primary Use	Safe to use indoors or out	Bonding most types of construction materials, especially where it isn’t easy to use fasteners
Cleanup (from skin)	Oil or petroleum jelly	Water
Cost	$3 to $20	$2 to $40