Gaps in poly panels of greenhouse

My contractors have finished putting up the 3-wall poly panels on the wood frame of the gh. When I went inside I immediately noticed some gaps along the bottom and top edge of some of the panels. I think it is the product of some of the panels being quite wide (6’) coupled with the nature of the connecting pieces. They are plastic and the top and base U-channel pieces are not fastened to the frame. The panels are held on by the side f-channels and the H-channels that connect one panel to another, both of which are screwed into the frame. So with the top and the bottom U-channels floating, there is enough flex in the panels that they create a gaps in the middle.

This is obviously no good since it will allow air in/out and bugs. So I’m trying to think of the best way to address it. One idea is just to use silicone sealer and caulk along the edges essentially gluing the panels to the frame/foundation at the top and bottom.

Another idea that I thought of (that I think I actually prefer) is to have them drill a fairly large hole (say .5”) in the bottom edge of the panels using a spade bit. Then use a screw and a neoprene washer to tighten the edge flush with the frame. The washer would be wider (say .75”) than the hole and the screw would be only tight enough to hold the panel down and not deform it, with the washer actually doing all the work. And then maybe some silicone along the edge as well.

The main concern is that the panels expand with heat. I believe they can expand a half inch. I’m assuming that is a general overall expansion and not a lateral shift. So I figure with a hole larger than the screw width it should allow for that expansion without causing a worry about cracks or bowing. And theoretically it should be able to move a bit beneath a neoprene washer.

So those are my main two ideas. I suppose there could be a bunch of other methods. Even something like double sided Velcro could work. More potent adhesives, the bottom edge could be covered with bricks, some boards could be attached to cover the edge and compress the panel to the frame/foundation, etc. etc. Any thoughts?

 

Here are some pics:
The first one is an attempt to show the top of the panel. I don't think the camera really picked it up but there is a definite gap.


This one shows the bottom surface on the outside where you can see an outter panel that is quite a bit wider (6') than the middle one (4' wide) and that they extend down past the top of the foundation:

And here is the gap from the inside. It seems to be mainly on the two side/wide panels at both the top and bottom whereas the middle panel has little if any gap:

 

The perforated material is vent tape which was recommended by the manufacturer apparently. Foil tape on the top edges. What looks like a metal channel is just a trick of the light. It is just one of the U-channel fittings over the top edge. And you're right about the 1/2" difference where it doesn't meet the top panel. For whatever reason, that panel is a bit lower than the other two. It may have just slid downward by gravity. I think I'll see if they can find a way to raise it up a bit. It is in the U and H and F channels really tight due to the tape and the tight tolerances so I don't know if they can push it up.

Thanks for the input on the gap issue. Looks like everyone agrees that a combination of sealant and washer head screws is the way to fix it.

 

Here are some new pics showing how they fixed the gaps:

This shows the bottom part of the side panels where they put what I think is too many screws of the wrong type:


And here is the bottom area of the roof panels where they used the technique and screws that are much more like what I envisioned. They might be screwed down a little bit too tight so I may end up backing the screws out a little bit.



I believe they did caulk the bottom with silicone but not the top. I'll probably end up doing that myself later.

 

Agreed. I probably should have just done it myself and then it would all be perfect. But at least now i'm not as worried about snails and sow bugs and other creepers getting in.