Exterior glues

Recommendations and opinions about various weather-resistant glues. February 13, 2001

We typically used a boatbuilding epoxy for exterior doors (Chemtech), and PVA glue (Franklin Titebond) for interior doors. We're now searching for a suitable exterior adhesive with: decent open time, good water resistance and durability, ambient fabrication temperatures of 60 degrees, and ease of use (single component would be nice).

We currently are testing Titebond II for doors not exposed to extreme weather conditions, and find it to be OK. The down side seems to be its temperature sensitivity. Does any one know how weather resistant a glue like this is? Any alternatives?

Forum Responses
National Casein has both a one-part and a two-part glue for exterior use. The two-part has a 24-hour shelf life. I have used both with great success.

A good summary of the various properties of woodworking adhesives is contained in the WOOD HANDBOOK, US Dept. Ag. Handbook No. 72, available from the Government Printing Office (or call your Congressman).

The following is a general description of major adhesive groups, but there are variations within each group:

AdhesiveMoistureTemperature FlexibilityColor durability
Melaminehigh lowlowcolorless
PVA - crosslink (Titebond II, etc.)highmoderatehighcolorless
Hot meltshighhighhighcolorless

Eugene M. Wengert, forum technical advisor

Many of the window manufacturers in my market use "outside" PVA white glues. These are called Type 1 bonds and are severely tested for outside exposure. They all take a catalyst to activate them. Companies which carry these are Jowat, Franklin, National Starch and National Casein. Some of these manufacturers are willing to send you free samples to try. The phone #s are listed in the Wood and Wood Products red book and in the FDM source guide.

We have had very good luck with Titebond II, even unexposed exterior applications. We have left samples in direct sun and rain for six months with no finish, and the glue joint has not failed. Also, an important feature of Titebond II is its suitability for use with RF gluing. You can glue up multilite windows that would be nearly impossible to clamp all at once by hitting them with the RF and moving on to the next muntin immediately.

Of course, the most durable exterior glue is resorcinol, however inconvenient. If using resorcinol, ALWAYS mix by weight, NOT by volume. Resorcinol is also particularly good with RF.

Has anyone used a product called "Gorilla Glue"?

I suggest you start by researching the federal specs on glue types. Type I glues are true waterproof glues. These include epoxy, resorcinol and catalyzed PVA. Type II glues are water resistant. These include Titebond I and II and urea formaldehyde.

I have used Gorilla Glue a little. I believe that it is a polyurethane glue. I have heard it was developed in Europe as a replacement for epoxy. When I ordered my glue from the Gorilla people, I asked them if it was a Type I glue. They did not know what I was talking about. I like Gorilla glue. It foams up as it cures, which seems to give it excellent gap filling characteristics. The moisture in the wood is the catalyst that cures the glue. It takes about 3 hours for the foam to harden. In liquid form the glue is difficult to remove from wood. It must be removed with mineral spirits or alcohol. After the foam has set it is also difficult to remove. It is difficult to prevent squeeze out due to the foaming action. The glue can also stain your skin.

We have used for a number of years a white PVA glue that is made in Europe, Japan and I believe also in the USA. It goes under various brand names such as "Koyo Bond", "Rakollit", etc. All of these are distributed in our region (Southeast Asia) to the woodworking industry.

This glue is a 2-component white glue with an isocyanate-based catalyst. The glue meets the DIN "B4" standard in Germany which I believe is the highest waterproof standard for the construction industry there. This glue is specified most times in the production of glue-lam scantlings (3" x 3-1/2" cross-section) that are used to make the German window frames for exterior use.

This glue is more tolerant of less-than perfect conditions, such as imperfect surface machining or a little bit too much moisture. I believe the glue is similar to a polyurethane (although it handles like a 2-component white glue) since it does expand slightly when curing. The glue is also advertised to adhere metal to wood and we have had cases where this happens on our machinery.

I do believe though that there are some restrictions in handling this catalyst and it might not be available in your market. National Casein also makes the glue so I am sure you can get more information from them about availability.

You could check the West System, Gougeon Brothers, Inc., for exterior door glues. They have good product literature and stocking dealers all over the country. I have two friends that build boats for a living and they both swear by the West System.

Check out a company called Systems 3 Resins. They are very good with bonding wood in exterior applications.

There have been a lot of spars and other marine items glued together with "weldwood". Mixed properly with water and applied to dry parts, it seems to have held up pretty good. I have not seen it in a while, but I think Elmer's has a product that is about the same. They also have a resorcinol type glue, but that is two parts and expensive.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
For doormaking, clamping pressure is not really an issue, so the expensive 5-1 epoxies that perform under weak pressure aren't worth the expense.

Resorcinol and plastic resins both like high clamping pressure, resorcinol for top-rate waterproofing and plastic resin for minimal cost at the expense of only a water-resistant bond.

Polys need high clamping pressure and perfect faying surfaces, but are expensive, though not as expensive as epoxy.