# Plastic lattice expansion problem



## Sleeper (Mar 24, 2009)

I don’t know quite how to explain this, but I’ll try with the help of a photo.

I posted earlier about had a problem I had with the deck screws breaking in my trellis and I’m now wondering if it was actually an expansion problem. I cut a 3/8” deep dado in my redwood frame to allow for expansion, but I did not think about contraction during the winter months at 18°F. 

I was just working on reinforcing it when it occurred to me that it is possible for one side to pop out if it were cold enough and expand enough in the hot sun to break the screws.

So I was thinking about centering the plastic lattice inside the frame with a couple of screws in the center to keep it centered and still allow for expansion. I’ll need two screws so that the lattice will not rotate and I’m concerned that the expansion might be too much for the screws when the surface temperature from the sun goes over 130˚F. I’ve never measured the temperature, but I know that I can’t pick up anything metal in the summer sun without burning myself.

Any other ideas to keep the lattice panel centered without the screws?


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## 4DThinker (Mar 13, 2013)

You are on the right track. I'd use three screws, with the center one fixing both dimensions centered. The upper and lower screws would be in a vertical slot to permit the lattice to move underneath them. That lattice will be expanding/contracting in length AND width as temp change.


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## Steve Neul (Sep 2, 2011)

I hate plastic lattice for a lot of the problems you are having. If it were me I would not put screws in the center where you are showing. You can pretty well count on it busting the lattice within a year even if you pre-drill and countersink a hole. What I've done is just nail a 1x2 over the lattice into the wood only and let the lattice float free.


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## Sleeper (Mar 24, 2009)

I’ve been thinking about the screws and remembered another plastic lattice that broke from screws that I used to hang it. I didn’t even screw it through the plastic but just had it hanging on them and it broke.

So I’m thinking of another idea of hanging it on block spacers with angle cut on the sides so that it could slide up or down with expansion but always remain centered. I know I want at least two blocks, one on each side, but not sure if I should use more. I would then rid a 2x4 to the same depth of the frame to hide them.


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## Steve Neul (Sep 2, 2011)

I think the blocks are unnecessary but I don't see any reason you can't use them unless you have problems with them busting when you shoot a nail through them.


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## Sleeper (Mar 24, 2009)

Steve Neul said:


> I think the blocks are unnecessary but I don't see any reason you can't use them unless you have problems with them busting when you shoot a nail through them.


 With ambient temperatures changing 25-30 deg from high to lows daily, I just don’t trust friction alone to hold it in place. 
I have to predrill everything otherwise everything cracks in this dry hot weather and my drill bits have to be sharp or the drill alone will crack it. The only exception would be green lumber.


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## Sleeper (Mar 24, 2009)

Oh well I never expected my 2x2 to split right down the middle even after drilling a pilot hole. 
I guess I should have used a larger drill because it’s pretty dry. I drilled an extra large hole for the block and it survived. 

I guess I'll have to make a trip to buy another Redwood 2x4


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