Next Generation Systems

Sustainable Solutions for building maintenance & repair

888-370-5420

Next Generation Systems offers engineered products for architectural repair together with innovative services to fully service your projects.

With over 30 years experience in wood repair, historic window surveys, cost estimates, and project management NextGenSys will be there from start to finish.

How Wood Repair Materials Fail: Brittle Epoxies & Adhesion Failure

Epoxies have been used to repair decayed and damaged wood here in the U.S. for at least 4 decades. The first materials that were developed ( and some still in use today ) uses an older epoxy chemistry that relies on micro-balloons to add thickness and to create a paste like consistency.

 Paste epoxy using micro-balloons

Paste epoxy using micro-balloons

As this older chemistry cures it age-hardens and turns brittle. 

These materials fail in two distinct ways: Adhesion and Cohesion failures. 

 

 Brittle epoxies crack as wood expands & contracts.                                              Photo above exhibits both adhesion ( left ) & cohesion ( right ) failure.

Brittle epoxies crack as wood expands & contracts.                                              Photo above exhibits both adhesion ( left ) & cohesion ( right ) failure.

Often the failure of the epoxy repair is not discovered because it is camouflaged as paint failure:

 Paint failure due to adhesive  and cohesive epoxy failure

Paint failure due to adhesive  and cohesive epoxy failure

Adhesive failure is caused either by poor surface preparation or an epoxy material that lacks a strong adhesive bond. 

Failure to remove gray wood ( click here for more information on gray wood and epoxy failure ) and decayed wood prior to the application of the epoxy will also contribute to adhesive failure.

Cohesive strength is the integrity of the material itself to move and withstand cracking under stress. Paste materials filled with micro-balloons lack the high flexural strength needed to repair wood.

Dura-Fix Slow Cure provides an excellent bond to wood fibers when used together with proper surface preparation. Dura-Fix is engineered with a high flexural strength to resist cohesion failure and will not harden with age.

 All photos above were taken during the Ft Totten Historic Landmark NYC  Restoration in 2006

All photos above were taken during the Ft Totten Historic Landmark NYC  Restoration in 2006

For more information on Dura-Fix Slow Cure contact: John@nxtgensys.com

 

Surface Preparation and Gray Wood

When working on older properties the durability of the old growth lumber used to fabricate the architectural elements is superior to lumber available today.

As this quality material gets exposed to the elements of sun and moisture the exposed surface begins to show signs of surface mold, graying and checking.

 Paint failure and exposed gray wood fibers.  No wood decay is present.

Paint failure and exposed gray wood fibers.  No wood decay is present.

Wood consists of lignin and cellulose fibers. When the wood is exposed to light the lignin breaks down and causes the cellulose fibers to break away.

Wood is like a bundle of straws held together with glue. The straws are the cellulose fiber, the glue is the lignin.

 

 A cross-section of wood cellulose fibers    

A cross-section of wood cellulose fibers 

 

Before conducting epoxy repairs or painting the surface it is necessary to remove all gray wood ( and any wood decay ). Failure to do so will compromise a solid bond to a sound substrate.

As the paint dries it undergoes a process called coalescing. This process creates stress on the substrate and pulls away loose paint and wood fibers. The sloughing of the damaged wood fibers results in paint failure.

 Paint failure due to the sloughing off of gray wood.   ( Note the gray wood fibers adhering to the underside of the failed paint film ) 

Paint failure due to the sloughing off of gray wood.

 ( Note the gray wood fibers adhering to the underside of the failed paint film ) 

Removing failed paint and sanding to bright wood is the only way to insure a solid bond to wood and provide a long lasting repair.

 Old window sash sanded to bright, uneffected wood

Old window sash sanded to bright, uneffected wood

888-370-5420           7 Marian Ct. Altamont, NY