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.

[leejosepho]

I grew up in an RV factory and was taught the fasteners (typically staples) are for holding pieces in place until the adhesive cures.

[johnfrwhipple]

The use of a construction adhesive like PL or Bull Dog adds one other factor to the equation. These types of adhesives also expand while they cure. This helps with things like squeaks and the lot. A sistered joist might "Squeak" after installed but with a little "Bull Dog" I think they have a better chance of staying quiet.

We like to use "Bull Dog" and Screws to set things in position and then nail it off. Often we will use a small pilot drill bit to drill though the old joist before nailing. Many old joist are dry and old. A wack of 3" Spikes can do more harm than good.

Jim's point on Chinese made nails is a very scary point. The quality of these Asian made fastners has been dropping for years.

Nails

Screws

Drill bits

Tool

I see this metal breaking like crazy. It was never like that 20 years ago. But then again 20 years ago my fastners where made in America or Canada.

JW

[chefwong]

FWIW, on screws, I am all GRK.
Spax is nice but I prefer the Torx head...
Spax is made in USA or Germany.

My GRK are coming out of Taiwan.
Favorites on GRK
R4 for framin Framing
Cabinet Screws and Trim Screws of Various Lengths
Their Caliburn Screws are badass. While it won't replace the Hilti Epox system...the caliburns are the ONLY concrete screw (non anchor) I use.

Shear or no shear....u should have seen the guys who were trying to remove my DIY stairs that was attached to wall stud framing..
Cursing like a mofo, as the 3" screws I used would not budge, the sawzalls were not cutting through it.


OUT comes the clamps when I'm sistering and using glue...
The construction adhesive does cause ~jacking~ --- even with the screws in.