Gluing, then screwing two pieces of wood for improved structural performance

[gfr92y]

Problem: The long side of my two-sided lattice fence enclosing my HVAC unit sags and is unsightly.

Situation: The homebuilder enclosed my HVAC unit with a two-sided lattice fence with one side being 102". Yes, 8' 6"! After time, the 2x4* with a 2x2* nailed to the underside began sagging. (*I do not know if the 2x4 and 2x2 were pressure-treated wood.)

Proposed Solution: Replace the 2x4 and 2x2 with a PT 2x4 and PT 2x2 assembled with a commercial-grade construction adhesive between the two and then screwed together.

Question: If the 2x2 was pre-drilled to allow the wood screw to slide to the 2x4, would screwing the 2x2 to the 2x4 after running a bead of glue between them create too much pressure between the two pieces of wood squeezing out too much glue and reduce the effectiveness of the glue?

Thanks!

gfr92y

[attachment=35368]

[barryvabeach]

I can't help with whether your solution will solve the sag problem, but the screws will not squeeze out too much glue,  especially 6 inches on center.  Most of us are more familiar with using wood glues- and there are waterproof ones like Titebond III,  rather then construction glue, but a few screws will not be an issue.  If the original one sagged,  consider whether you can change the dimensions -  like adding another 2 x 4 to the bottom rail, or adding posts to cut the open span length.

[gfr92y]

I can't help with whether your solution will solve the sag problem, but the screws will not squeeze out too much glue,  especially 6 inches on center.  Most of us are more familiar with using wood glues- and there are waterproof ones like Titebond III,  rather then construction glue, but a few screws will not be an issue.  If the original one sagged,  consider whether you can change the dimensions -  like adding another 2 x 4 to the bottom rail, or adding posts to cut the open span length.

You and the other respondent have given me enough information to proceed and/or make some helpful design changes.

Thanks!

gfr92y

[MT Woodworker]

Depending on what I am building, for indoors or outdoors, I have glued and screwed joints many times with no issues.

[gfr92y]

Depending on what I am building, for indoors or outdoors, I have glued and screwed joints many times with no issues.

You and the other respondent have given me enough information to proceed and/or make some helpful design changes.

Thanks!

gfr92y

[toolmiser]

Are you going to bend it straight or even a little bent the other way before gluing on the new piece? Otherwise you are just reinforcing the "sag"

[jteneyck]

If you use PT wood it will still have some and sometimes a lot of moisture in it.  If so, make sure the adhesive you use is rated for PT.  FWIW, Gorilla Glue works really well in this application.  

John

[Cooler]

I would also note that when I enclosed (3 sides and open at the bottom) my through the wall air conditioner with a plastic lattice to partially hide the unit, the compressor cycled off and only warm air came out of the A.C. 

I removed the lattice and it started to cool again.

I would note that there is very little ventilation above the AC due to the large overhang of the soffit. 

Just one more thing to be aware of.

[lift mechanic]

I think I would use a 1/4" x 2" x 2" steel angle iron and bolt it through. Use some "cold galvanizing" spray coating to help prevent rust before installing.

[BrentDH]

If nothing else I would turn the 2x4 on edge and then add the 2x2. Even better change the 2x4 to a 2x6.

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