Adhesives, Fasteners, and Simulated Disasters

February 27, 2016

 

How much stronger is a house with key parts glued and nailed together rather than just nailed together?

 

To get a ballpark understanding, Linn builds two models: one with metal fasteners only and one with glue and metal fasteners. 

Then she runs a couple of 'tests' -- the benchtop opposing-clamp-earthquake-simulation-test and the Honey-we-bought-a-house-next-to-a-lacrosse-ball-factory-in-a-hurricane-zone-test.

 

Test 1: Does glue help hold a house to its foundation in an earthquake? 

On one model, Linn fasteners to the foundation with only bolts. On the other model, she glues the sill plate to the 'foundation' in addition to foundation bolts. 

Using a couple of bar clamps, she pulls opposing plates perpendicular to simulate an earthquake. 

Results:
  • No glue: the weak point was in the middle. A gable wall collapsed buckling as a hinge at the top plate and the corner breaks apart. The opposite end held up well. 
  • Glue and nails: No failure at the gable end or corner. The bottom plate broke at the point of force, and it took significantly more force to break it. 
 

Test 2: Does glue in a framed wall assembly help with impact resistance?

(the lacrosse ball test simulating a hurricane near a giant lacrosse ball factory). 

Lynn sets up a pendulum with a lacrosse ball attached and chucks it at the models.

Results:
  • No glue: shatters the gable end with a single throw
  • Glue and nails: no damage from the first two throws. The third row is much harder and it busts out the center stud, but the gable assembly remained intact. The glue joint did not break, the wood broke. 

Next, Lynn gets a bigger wrecking ball — or wrecking bell as it turns out. After whacking the gable end with a giant cast iron bell, only one rafter breaks free. 

After additional repeated bell whacks, the rafter at the opposite end breaks loose, and Linn declares a winner: 

"I think the one with the glue performed unbelievably better. "

Womp.

If you intend to build a house and want some extra strength, Linn recommends using some construction adhesive. And not building next to Liberty Bell factories. 

Of course, both structures performed rather well — neither failed. If people were inside they would have lived.

Especially if the houses had structural sheathing on them which would distribute both shear and impact force. 

 

—Linn learned woodworking as a kid in school in Sweden. Her store, at DarbinOrvar.com, sells woodworking mallets and finishing wax. Her YouTube channel has a lot of 'Make' videos. She lives in Corvallis, OR.

 


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