Mounting HDU to 4x4 post

trichosirius

New Member
Hi guys, new to the forums and looking for some advice on mounting HDU signs to wood 4x4 posts.

The signs are roughly 20"x15" and I am thinking I'm going to need some kind of backing to keep them from being broken. My thoughts were first mounting a backing to the post, then affixing the HDU to the backer with Epoxy and screws.

What would you guys advise as a backing material? We have lots of .08 aluminum in house so it would be great if that would work.
 

TimToad

Active Member
Depending on its size, we typically laminate our HDU to either 3mm or 6mm Alupanel or 1/2" MDO with Titebond polyurethane glue as a backer. By rolling the glue over the entire surface and sandwiching them together with clamps and weights it creates a super strong, waterproof seal. We triple seal the edges and then apply a couple coats of our finish color
 

Billct2

Active Member
Single face signs right? In that case and at that size .080 is fine. I like the idea of mounting the o80 first then fixing the HDU to that.
You can us a construction/polyurethane adhesive and screws into the back.
 

trichosirius

New Member
Depending on its size, we typically laminate our HDU to either 3mm or 6mm Alupanel or 1/2" MDO with Titebond polyurethane glue as a backer. By rolling the glue over the entire surface and sandwiching them together with clamps and weights it creates a super strong, waterproof seal. We triple seal the edges and then apply a couple coats of our finish color
This sounds like a good plan. How does the MDO move in relation to the HDU? Any concerns about expansion/contraction causing issues with the lamination?

Single face signs right? In that case and at that size .080 is fine. I like the idea of mounting the o80 first then fixing the HDU to that.
You can us a construction/polyurethane adhesive and screws into the back.
Single face, yes. This is my go-to plan at the moment, I suppose my primary concerns with the aluminum or any backing is expansion or warping of the material.
 

Billct2

Active Member
I've used aluminum without any adverse results that I know of. I've also used ACM and Alumalite. I don't like using anything with wood after issues of wood rotting when we first started using HDU
 

GB2

Member
I hate to answer a question with a question but how thick are the signs you are doing and how will they be mounted to the post....single post or two? 20"x15" is typically not large enough to worry about unless you are using thin material or if you are mounting them to a single post like a traffic sign. We try to use internal steel frames as much as possible. Again, I don't think these are large enough to worry much about dissimilar materials expansion and contraction, adhering them to aluminum or ACM should be fine. Don't ever use MDO with HDU.
 
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TimToad

Active Member
This sounds like a good plan. How does the MDO move in relation to the HDU? Any concerns about expansion/contraction causing issues with the lamination?

Single face, yes. This is my go-to plan at the moment, I suppose my primary concerns with the aluminum or any backing is expansion or warping of the material.

I wouldn't use MDO as a backer on the size sign you asked about, but the one in the photo is about 3'x4' and we used it for that. I wanted to make sure that bottom portion had some good backing to it.

I understand the concern about expansion/contraction but the materials are probably pretty similar in that department and we're in a location that gets only 15-20 inches of rain in a good year. As with anything, we try to match things on an individual basis. We're mainly doing it for added rigidity and to give us something better to grab our installation bolts, screws, etc..
 

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John_Smith

Enjoying retirement in Central Florida
I have done bunches and bunches of just this type of signage.
I put many stainless large head screws right through the face
of the sign, cover with exterior latex caulk, and touch up the paint.
and hope for the best. if someone wants it, they will get it. period.
I have never had one broken from regular, non-abusive use.
 

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3Dsigns

New Member
The way I do it, for 1 sided signs, is to laminate "backer boards" of HDU to the back of the sign with Gorilla Glue(polyurethane). I wet the back of the board, run strips of GG on it and screw it to the back of the sign, only about 3/4"" in or so is sufficient. I countersink the heads just enough to fill them with FSC88WB filler(Coastal Enterprises). When that cures, I cut the squeeze-out with a sharp chisel. Place the backer boards exactly where you want the posts. Pre-drill the posts and screw them to the backerboards with galvanized lag screws. Usually a 3/8'' to 1/2'' diameter screws are sufficient and only three lag screws per board is enough; depending on the size of the sign. Screw them in snug, no pilot hole is needed, just dont strip the HDU when the screw bottoms out. I have done a hundred like this and never had any failures except one: It was run over by a bull dozer, broke one post, and ripped the screws out of the other but both backer boards were not de-laminated from the sign. What you are doing is gluing the same materials, using a glue of essentially the same material like a "weld" if you will.The following is a step by step on sign restoration I did several years ago, but the first photo shows how the backers are attached on some of my redwood signs the same way. http://www.letterville.com/steps/wayne/index1.htm
 
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