Gate Post Hole Through Rock

[Obed]

Eddie,
Actually I was thinking of hanging the gate on the corner post. Please see attached drawing. I was thinking I would create the corner using 3 posts at a 90 degree angle. The 3rd post that does not have barbed wire is just there to support the weight of the gate as it opens. I would 2 have H-braces between the 3 posts using 4x4x8' horizontal braces.

As I have no welding skills or equipment, I was planning to use wooden posts. I may go with one of the lighter weight gates as there is no livestock to contend with. Now creating a concrete footer is an interesting suggestion. I might try that if I can't get the holes dug. However, trying the spud bar is worth a try because sometimes around here the sandstone is pretty soft. I just won't know until I attempt it. I can't say I'm in love with the idea of spending $170 to rent a rock drill and compresser and buy a couple rock bits.

 

[wroughtn_harv]

I need to put in a 16' farm gate at the entrance to our property. I only have 1 foot of dirt before I hit what I'm assuming is a solid sandstone base. How do I dig a 3 foot deep hole in this stuff?

I can rent a 3PH post hole digger but they don't have rock augers available. I can rent a hydraulic jack hammer for $93/day with a 3 foot bit. I can also rent a rock drill and compresser and buy a couple rock bits for $167/day. I don't have access to electricity where I will be installing the gate.

What is my best option?

Go with the rotary hammer and compressor. You can be done in a couple of hours, post set, whole match, owning the trophy.

If you're sure the stone is good then all you need is a hole one and a half times the diameter deep. Once you're past that you're doing it for exercise. If the stone isn't really good then you need to go deeper.

I'd use a three and a half inch bit with two and a half inch schedule forty pipe posts (2 7/8" O.D.)

The secret is to use a quick setting hydraulic cement like Pour Stone or Quick Rok. You can buy fifty pounds of Quick Rok at your local fence supplier for around twenty five dollars or less. With a decent temperature you can have a post set and ready to work twenty to thirty minutes after pouring. You'll have a bunch of Quick Rok left over. You can use that where you're concreting in fence posts with regular concrete and want to work it sooner. You can set posts with concrete with Quick Rok added and work them the same day without worrying about breaking loose.

Here in north Texas we don't have rock. We have an Austim stone that is comparable to Caliche out west and we have a blue shale that can be hard. But when I set fence in So Cal many years ago we worked in granite areas. The rotary hammer and hydraulic cement worked best. I still carry bits for rotary drills on my truck here in Texas because sometimes I'll use a rotary hammer and compressor for setting posts in concrete slabs etc.

 

[Obed]

Harvey and Eddie,
Wow - posts from both of you! I feel quite privileged. I've looked at work from both of you and have been really impressed with your work. Harvey, I've thoroughly enjoyed going through your "Fun With Gates" section of your website. You have really turned fence building into quite an art. Eddie, I was captivated by your "Container Barn" write-up. You have a nack for coming up with very practical and useful projects.

Hopefully this Christmas weekend I'll be able to dig up with my CUT backhoe
a spot a few feet from where the gate posts will go so I can find out what the rock is like. With that information I'll go shopping for some posts.

Thanks so much for your input. Believe me I'm really taking it all to heart.

Obed

 

[Obed]

I'd use a three and a half inch bit with two and a half inch schedule forty pipe posts (2 7/8" O.D.)

Harvey,
Can I set up these types of posts and hang a gate on them without welding or needing any special tools?

Thanks,
Obed

 

[vallyfarm]

I don't live near sandstone, just clay and alot of rocks, but couldn't you drill into the stone and bolt a cement slab to it? the cament could hold the post, and the rock can hold the cement. Build the post like a large "L" across the stone and have it bolted down, with a cement slab bolted down over it might work. It's just a thought. Let me know if it won't, and why please. Mike

 

[Brad_Blazer]

I was thinking on similar lines - If the stone is really solid could you use concrete anchors? Instead of bolting a slab to the stone use a post with a base plate. Where I work they have safety rails made to withstand forklift impacts - something like 4 tons at 5mph. They are on posts with base plates.
Safety Railing, Industrial Safety Railings, Protective Guard Rails, Steel Guardrails
You might be able to have a welding shop fabricate the posts complete with gate hinges but it might get expensive.

If the stone is solid, but not as strong as concrete you could make deeper holes, say 1" OD x 12" deep, fill with the hydraulic cement, and insert a piece of allthread. Hilti actually makes some pretty cool adhesive anchoring products. They use an epoxy concrete adhesive with a dispenser like a double barrel caulking gun with a static mixer nozzle. Some of their adhesive anchors are simple allthread.
Chemical - Hilti USA
Hydraulic cement in a clean hole should be just as strong - just not as convenient.

The advantage I am thinking of is using an SDS hammer drill that will run off a small generator or even a inverter vs. a full sized air hammer. I have a cheapie SDS drill and bits like this and they work good in concrete e.g. bit still in great shape after 50 holes.
Harbor Freight Tools - Quality Tools at the Lowest Prices
Harbor Freight Tools - Quality Tools at the Lowest Prices

Just some ideas. Depending on conditions and what is available in your area they may or may not work out.

Brad

 

[wroughtn_harv]

Harvey,
Can I set up these types of posts and hang a gate on them without welding or needing any special tools?

Thanks,
Obed

You can use conventional chainlink bolt up brackets and construction techniques. You can purchase and use clamp on hinges for your posts. After they're bolted tight then you drill through the bracket and use a self tapping metal screw into the post as a lock to hold the hinge in place. The same thing with brace bands and rail ends to hold your cross braces in place.

Visit a chainlink fence that's been done right by a real industrial fence company. Usually you'll find one at an industrial site or public facility where things are built to engineered standards. You can see the techniques and brackets you need.

Good luck.

 

[RedRocker]

RedRocker,
What's that get-up going to cost to rent for the weekend?

Right at $400 bucks for 24 hours, heckuva deal since I know what it's like doing it by hand.

 

[Obed]

The advantage I am thinking of is using an SDS hammer drill that will run off a small generator or even a inverter vs. a full sized air hammer. I have a cheapie SDS drill and bits like this and they work good in concrete e.g. bit still in great shape after 50 holes.
Harbor Freight Tools - Quality Tools at the Lowest Prices
Harbor Freight Tools - Quality Tools at the Lowest PricesBrad

Brad,
Thanks for the links to the SDS drill. I didn't know what these were. What I don't understand is how to use it in my scenario. I will be digging a post hole through dirt about 12 to 18 inches deep. Then I hit rock. How can I reach the rock to use this tool through a narrow post hole in the dirt?
Thanks,
Obed

 

[Obed]

I bought a digging bar and tried it out to see how difficult it would be to dig through the sandstone with it. So I dug a test hole down to the rock near the gate location with my tractor's backhoe.