What is the purpose of liquid nails when sistering joists

[chefwong]

What is the purpose of construction adhesive when sistering joists.
Hell, I just do it because....I do it.
There is no structural integrity gained when doing it.

Whether you screw it or nail it *another hot contested fastener debate in itself*, what do you gain by using any sorta construction adhesive when sistering joists.

[christoff]

because mike holmes says so lol!

[hj]

You gain the same peace of mind that you would have if you held up your pants with a belt AND suspenders.

[jch]

I would think that the construction adhesive would make the wood-to-wood joint stiffer and prevent the joint from loosening over time (say if a strong live load were on the joists).

I know the BC Building Code states that only nails (not screws) are approved for use in attaching anything structural/load bearing. Probably because screws have to be made of a stiffer (and therefore more brittle) metal than nails. In an earthquake (BC is an earthquake zone), screws snap whereas nails bend.

My neighbour used deck screws to attach the wooden treads to his new porch steps and, within 2 weeks, 1/4 of the edge treads had screws that had snapped. He reattached them with nails and hasn't had any problems since.

[jadnashua]

A good glue, properly installed and set, bonds the two pieces together into one effective piece rather than two. Think of plywood or a glulam. Not all screws are created equal - the tensile strength, bending, and ductility varies all across the board, then you have the issue of quality control (some of those made in China are truly horrible). SS, while it may not corrode, depending on the alloy and processing, is relatively soft and weak compared to a typical construction nail.

[hj]

If the two boards are fastened together, any movement would have to "shear" the fasteners, not bend them.