Using Construction Adhesive... Constructively!

Constructive uses for construction adhesives.
Construction adhesive refers to a broad range of similar products used to bond common materials used in the construction, renovation and finishing of homes. Of course, if you have shopped in a hardware store you know that some companies have adhesives they have named "construction adhesive".
In the context of this article, I am speaking of a class of adhesives that share certain properties. The basic characteristics of these products are:

• Available in cans, squeeze tubes, and caulking tubes
• Thick pasty consistency; applied with putty knife or notched trowel
• Water or solvent based
• Can fill gaps and imperfections in materials
• Will adhere to a wide range of building materials
• Tend to remain flexible after drying
• Waterproof or water resistant
• Usually dry within 24 hours

Choosing the correct construction adhesive product can be confusing, since there is lots of functional overlap among them. Fortunately, the manufacturers are pretty good about listing the uses of their products on the labels. Some of them are quite specific... "for ceramic tile only", for example. Others label their products for broader uses... the more generic and well known "construction adhesive", a generalist that can be used for wide range of adhesive tasks.

Some construction adhesives that work wonderfully on indoor wood will not stand up to the moisture and temperature changes of exterior work. You only get to choose once, so choose wisely.

There are two ways construction adhesive is applied.
Construction adhesives is applied either in beads or full coverage. Beads are lines of adhesive that are applied to a surface with the use of a caulking gun. This is the most economical use of construction adhesive and typically used for the gluing of large, flat materials to large flat surfaces. Some common uses for the bead method are in the installation of plastic tub surrounds over drywall or ceramic tile, wood paneling to any smooth wall, and attaching drywall to studs.

Full coverage is used where the material to be glued is small, such as floor tiles or ceramic tile, or where an absolutely solid surface is required, which includes virtually all flooring applications with the exception of carpet over padding and some types of vinyl flooring.

All full coverage adhesive jobs require the use of a notched trowel to apply the adhesive. You may be tempted to just slather the adhesive on with a putty knife... and you might get away with this for a small repair. But there are five sensible reasons for doing it right, though the product labels won't tell you why... they just say to do it their way or else! In a nutshell...

1. Saves adhesive... using a notched trowel can save you up to 50% on the adhesive used over a flat trowel or wide putty knife!
2. Consistent thickness of adhesive... Remember that most construction adhesives tend to stay flexible. Applying too thick an application can cause a soft spot in the floor, producing movement in the material. This may not be as critical with interlocking wood parquet flooring but it can be a disaster with ceramic tile!
3. Shortens drying time... those little grooves flatten when the material is pressed into the adhesive giving a thinner glue film. Thinner coats mean less drying time. An overly thick adhesive coat can take weeks to dry properly
4.  Better adhesion...  the "peaks" produced by troweling increase the chance that the material will grip firmly to the adhesive.
   
5. Less shrinkage... as the adhesive dries, it will shrink. This is not an issue with a thin coat. But if a thick layer is applied, the material you are gluing may noticeably move or settle! This is why you should never build up a depression in a floor or wall with adhesive alone... use a floor leveler or wallboard compound to flatten the surface before your gluing effort!
   

Be careful when choosing a construction adhesive!!
Certain applications and materials require special construction adhesives. Plastics are especially sensitive to poor adhesive choices! So when installing products such as tub surrounds and vinyl cove base, be sure to use an adhesive recommended by the manufacturer. Otherwise, you may find that the adhesive's solvent will actually migrate through the plastic, causing noticeable staining on the surface! This solvent "creep" can be a sneaky process... it could take weeks to occur, long after the job is done. Needless to say, you will not be a happy camper!

Note the drying times on the packaging!
Construction adhesives in many cases do not reach full strength for a week, so if you want the job to last give them plenty of drying time before applying full stress to the joint.
One of the more popular lines of construction adhesive is manufactured by the PL Company. Their line includes the old favorite Pl200 general purpose construction adhesive, as well as special formulations for plastics and foam and an exterior wood flooring adhesive purported to be as "strong as nails"! Another major player in this area is Macco, manufacturer of Liquid Nails, a full line of construction adhesives for virtually all materials, indoors and out.