Reply by clin

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Posted on Wise use of glue on exterior work?

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1030 posts in 1381 days

#1 posted 07-09-2018 12:13 AM

Pics helped a lot, but I still have a few questions. If I understand this correctly, the frame is made up of a pressure treated center and 1/2” ceder on the outside of that. The ceder overlaps the PT wood such that it forms the grove that traps the panels boards. The panel boards will be vertical?

If I have this correct, I agree with Aj2. Put a single fastener in the center of each board. I recommend a stainless steel brad. Stainless won’t rust and therefore won’t react with the tannin in the wood and make black streaks. An alternative would be stainless or brass screws. But, on the back side of the gate, you can just shoot a brad in at an angle. It will be so small it will be unnoticeable.

NO GLUE, on the panels boards anywhere. The exception would be to not use a fastener and just put a dab of glue in the center of each board.

This will allow each board to expand and contract from its center. The boards need to be spaced far enough apart that when they swell, due to rain etc., they will not push against each other too much (best if not at all).

If you need the gate to be solid (no gaps you can see through), you can tongue and groove the panel boards. Then when you install them, put some space between them to allow for expansion. Meaning don’t push the boards tightly together. Especially if they are known to be dry. For example, an 1/8” gap. The T&G will keep the gap from opening all the way through, as long as the T&G is deep enough.

It is possible to not even use a fastener in the boards and just allow them to float. The problem with this is any gap or tongue and groove spacing is not likely to be evenly distributed. So unless your T&G were unusually deep, a gap all the way through the boards could show.

I just found this wood shrinkage/expansion estimator. You can look up the temperature and relative humidity data for your area and plug it in. You want to look at seasonal, NOT daily temperature and humidity.

In any case, 2% movement is realistic. Assuming a 40” wide gate, that’s over 3/4” of total expansion and contraction.

Water will collect in the bottom frame member due to the groove that traps the boards. This is where I would put weep holes. Just drill 1/4” – 3/8” or so holes through the bottom of this. I’ve spaced these about 6” apart and used a chisel to slope the bottom of the groove towards the holes. This slope probably doesn’t do much of anything. Just don’t make the holes so large or frequent that they reduce the strength of the frame significantly.

They can’t be seen since they are on the bottom edge of the gate. That way, any bulk water can drain out. I live in a very dry climate, and I had an existing gate on my house that did not allow for this drainage. And it all rotted out in less than 10 years. We get 6” a year or so of total rain. Like I said, dry.

Remember, even rot resistance woods like ceder or PT, are just that resistant. So anything you can do to reduce the amount of time it is exposed to water, the better.

FYI, an alternative is to make the bottom a tongue and grove where the groove is in the ends of the panel board and the tongue on the frame. This way there is no place for water to collect. In your case, this would require the PT wood to stick out from the ceder and be cut to form the tongue.

Something to consider doing is to putting a slight slope on the top edge of your bottom ceder panels. The idea is to help water drain away and not stand on this edge or even funnel into the gap. Tops of gates are often slightly sloped as well so water doesn’t stand on them.

Rather than drainage holes, what about sealing it with silicone? I m curious because I bought an 18th century panel made of approx. 5/16” metal bent into a fairly complex mesh pattern. I m going to be using it in the center of a gate similar to the OP s. I haven t begun construction, but how to deal with the groove it will sit in on the bottom rail is a concern. I m not trying to hijack the thread, since whatever solution works for one will work for the other.


- Rich

I don’t think there is ever a good way to seal external wood, water tight. Water always seems to find a way in. And the way the wood expands and contracts makes it so hard to keep a seal. I think if you try to seal it, water will get in, and then the sealant will just make it take that much longer to dry out.

I do think there is value trying to seal the top of a structure, to shed as much water as possible. But something like this near the bottom, where water could collect, I think it’s best to figure out how to get the water out as easy as possible.

-- Clin

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