Wednesday, March 27, 2013

High tensile fence installation

I've been working on the fence out at the property again.  We spent spring break out there and I went out again last weekend by myself.  We're using a method I found in a Bekaert installation guide to set the posts.  I'd never heard of this before, but it seems like it is working very well.  You pack 8 inches of dry concrete at the bottom, then alternate 6 inch layers of concrete and soil the rest of the way up the hole.  After doing this, I realized that I don't think we ever packed posts correctly when I was a kid.  We always filled the hole up, then packed down the dirt.  Then filled it up again and packed the dirt.  And we just kept doing that until we couldn't pack any more in.  Our posts always had a good bit of wobble in them, and it's probably because the bottom of the hole, especially with a really deep hole, never really got packed.  But this Bekart method forces you to pack it in layers all the way up, so it is evenly packed all the way to the bottom of the hole.  These posts we've put in seem to be completely solid as soon as we are done packing them, and we don't have to haul water and a wheel barrow around to mix concrete or anything.  I want to say they are just as solid as they would be if we poured concrete, but I don't really want to lean into one enough right now to determine if the tiny bit of movement I see is the ground around the hole or the dirt in the hole.  At worst, they are "almost" as secure, and I'm confident that will change to "absolutely as secure" once the concrete layers finally cure.

I'm also experimenting with a different H-Brace method.  According to everything I have read, the h-brace cross member has to be two and a half times as long as the fence is tall.  For our 4 foot fence, that's a ten foot cross member.  The documents all suggest a 4 inch pole as a cross member, but I don't see how any wood is going to work long-term at 10 feet supported by its ends.  Sure, if it's pressure treated it may not rot, but it's still going to get soaked when it rains and risk sagging.  So I'm using 1 inch galvanized pipe as my cross members.  They're not as strong if you sit on the cross member as a pole would be, but they are only meant to absorb force long-ways, not up-down (compression, not bending) so it should be fine.

I also tried to cheap out on brace pins.  These are supposed to go through the upright post and into the ends of the cross member to support it.  Even though I'm using pipes, I still needed these to hold the pipe up, and I found that zinc-plated hex bolts were cheaper than actual brace pins of the same length.  Unfortunately, I also found out that the new(ish) compounds they use in pressure treating eat through the coatings very quickly, even on heavy galvanization.  So my bolts may not last long.  The hot-dipped galvanized is what is recommended, but even that will corrode.  So, instead of pricing out hot-dipped galvanized bolts vs the "class III" galvanized brace pins, I just decided to use a 1 3/8" forstner bit to drill a pocket about an inch deep into each post.  I then left the plastic thread protector on the end and set the pipe in the hole.  I don't know what "class" the galvanization on pipe is, but hopefully the plastic cap will help protect it from reacting regardless.  So far, the assemblies look very nice, even with the crappy home depot posts.  I'll put a picture up as soon as my phone starts working again (I took it on my camera phone, and can't currently get it off).

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