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700 lb Gate post hole size calculation
- Thread starter PascalG8
- Start date
- Replies 43
- Views 6,746
Rob F.
Diamond
- Joined
- Aug 5, 2012
- Location
- California, Central Coast
Depends on the soil.
Tony Quiring
Titanium
- Joined
- Nov 5, 2008
- Location
- Madera county california usa
2 ft deeper than your finished size.
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Tony Quiring
Titanium
- Joined
- Nov 5, 2008
- Location
- Madera county california usa
12 ft is a good moment so the post itself may give way as well.
Consider filling post with concrete as well.
Depth may need to be 6 to 7 feet with a good amount of concrete but it depends on soil and drainage.
Your local building inspector can be asked as they usually know these things for your area
Sent from my SAMSUNG-SM-G930A using Tapatalk
Consider filling post with concrete as well.
Depth may need to be 6 to 7 feet with a good amount of concrete but it depends on soil and drainage.
Your local building inspector can be asked as they usually know these things for your area
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johansen
Stainless
- Joined
- Aug 16, 2014
- Location
- silverdale wa
Bolt the gate post to a flange set in the cement. In the event the soil moves you can shim the flange
I_AM_MACHINE
Aluminum
- Joined
- Jul 14, 2015
- Location
- Nebraska, USA
The weight of the gate is producing a 4,200 foot-pound (700 x 6')overturning moment on the post. The soil has to be able to counteract that force. Poor soils have a shear strength of around 20 kilopascals, while stronger soils have a shear strength of 80+ kilopascals. In poor soils you would need nearly twelve feet of embedment in the earth to have enough surface area of the post in order to not exceed the available shear strength of the soil. In strong soil, only three to four feet would be necessary. It really depends on the characteristics of the soil. If it were me, I would dig a hole five feet deep, three feet wide on each side, pour one cubic yard of concrete (weight approximately 4,000 pounds), and either embed or affix the post to the concrete.
I_AM_MACHINE
Aluminum
- Joined
- Jul 14, 2015
- Location
- Nebraska, USA
Clay soils typically are on the lower end of the shear strengths I listed. I would definitely go the concrete route.
Rob F.
Diamond
- Joined
- Aug 5, 2012
- Location
- California, Central Coast
If you do the concrete base it is important to have the bottom of the hole flat with all loose dirt removed and sharp corners where it meet the walls. If the bottom is deeper in the center it will not help to resist the base from rolling over. It's also a good practice to taper the base a bit wider at the bottom if you can.
sealark37
Stainless
- Joined
- Mar 24, 2010
- Location
- Davidson NC USA
Find the minimum yardage charge on delivered concrete. Don't skimp. The above info is good. Take the time to fill the post. If you do it right, you won't have to lift the gate in your old age. Please don't ask how I learned these facts.
Phil in Montana
Stainless
- Joined
- Jul 31, 2007
- Location
- Missoula Mt
Big enough for a yard of cement...Phil
4GSR
Diamond
- Joined
- Jan 25, 2005
- Location
- Victoria, Texas, USA
Call before you dig. You never know what you may hit...down there.
deltap
Cast Iron
- Joined
- Sep 3, 2004
- Location
- Wisconsin, USA
Also use the threaded L shaped hinge pins so you can adjust if the post moves a bit. A ground contact wheel on the latch end will take the load off the post.
dalmatiangirl61
Diamond
- Joined
- Jan 31, 2011
- Location
- BFE Nevada/San Marcos Tx
12 ft depth, use 2' sonotube and fill with concrete for base.
I_AM_MACHINE hit the nail on the head for sizing.
I have a couple of gates very similar to yours, each about 100lbs lighter. Soil is the same, Clay. Most people overlook Wind Load on a gate since most gates of this size usually are ornamental types. The reason I bring up wind load is that it adds additional shear load to the footing depending on the surface area of the gate and wind speed.
My gates each have the same post you are using. Each footing is 3' x 3' square and 4-1/2' deep. Each footing has a rebar cage that is 24" square and 12" between each layer using #4 rebar. Rebar is cheap and the benefits are greater than the cost, after all buildings have rebar in the footings and load bearing/shear wall footings.
Hinges are a matter of preference as long as they can handle the load. Do a search on the internet for gate hinges. I used the type that has a Tapered Roller Bearing for the bottom of the gate and a Ball Bearing for the top hinge. There is a gate on each side of the driveway and neither one have ever sagged (without a wheel on the end) or given me a problem, even with my fat ass hanging on the end of them.
They have been in place for over 6 years now.
Best of luck on your project!
I have a couple of gates very similar to yours, each about 100lbs lighter. Soil is the same, Clay. Most people overlook Wind Load on a gate since most gates of this size usually are ornamental types. The reason I bring up wind load is that it adds additional shear load to the footing depending on the surface area of the gate and wind speed.
My gates each have the same post you are using. Each footing is 3' x 3' square and 4-1/2' deep. Each footing has a rebar cage that is 24" square and 12" between each layer using #4 rebar. Rebar is cheap and the benefits are greater than the cost, after all buildings have rebar in the footings and load bearing/shear wall footings.
Hinges are a matter of preference as long as they can handle the load. Do a search on the internet for gate hinges. I used the type that has a Tapered Roller Bearing for the bottom of the gate and a Ball Bearing for the top hinge. There is a gate on each side of the driveway and neither one have ever sagged (without a wheel on the end) or given me a problem, even with my fat ass hanging on the end of them.
They have been in place for over 6 years now.Best of luck on your project!
thermite
Diamond
- Joined
- Sep 21, 2011
Re-think it.
Picture a paved carpark.
"H" shaped frame. Large OD galvanized pipe OR medium I-beams OR Heavy pressure-treat timber OR ferrocrete OR precast reinforced concrete beams if you are into that sort of s**t.
Crossbar of the "H" is your opening, plus 1/4 of it past, each end.
For a 12 foot opening, that's an 18-foot beam. Composite is OK. Need not be one-piece. TWO parallel runs are OK too, pipe frame especially.
"legs" of the "H" are each half the crossbar long, 1/4 of the opening in from its ends.
For your 12-foot opening, they are six feet long, cross 3 feet in. Longer, swing-open side, is OK, too.
Diagonal braces run at a 45-degree from 2/3 height of posts down to wherever TF they hit the base frame, three sides of each post. Eg: not at the open side.
ONE sandbag at the end of each of the "verticals" of the "H"?
Your gate should NOW be stable sitting naked on the carpark surface.
You could dooo that "surface mount" by making your "H" verticals become kerbs.
Otherwise, rent you a trackhoe. Cut your trenches to fit, prepare to bury as deadmans.
Compact 3" gradation bluestone O/E (VDOT 21A here). Concrete optional
Set the above H+ frame, level and plumb. Concrete optional over.
Compacted gravel, crusher-run, then ignorant dirt will do yah.
Soil type no longer much matters. It was Monongahela Red, our case.
Dunno if it is good for more that 70 years or not.
We only kept the farm for 80 years.
The "BFBI" (Brute Force and Bloody Ignorance) way AKA "more 'crete, please, we're REDNECKS!" is simply too hard to predict, wants holes dug too deep for good sense. Rock was under that clay soil.
Support wheel at the swing end is nearly ALWAYS a good idea. Very nearly. Do not skimp. Use a decent sized one.
Two six-foot leaves are waaaaay easier than one 12-footer.
Rolling bypass / sliding / telescoping gates are USUALLY better than swing. No cantilevering required.
2CW
What part of
did you not understand? The OP didn't ask for how to design and build a gate. He gave us what he had to work with. Since he asked for the size and depth of hole in the ground, one can assume that the 6" post is not long enough to drive it down 20 feet or more. Concrete is cheap compared to what a gate of that size cost and is a well respected method of construction, certainly not REDNECK.
What's wrong with Cantilevering? It's been around a lot, lot longer than 80 years. Frank Lloyd-Wright used it in his "FallingWater" design, I guess he must have been stupid!
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