Gate

[Blackwaterforge]

I am building a pair of driveway gates for a customer.

Gates will each be 7' long x 5' high and weigh 450 lbs.

Contractor has installed 6x6x1/4 post 4' deep in 3' square hole filled with concrete.

Post will be wrapped with masonry.

Will these single post be sufficient?

Thank You!

 

[DSW]

You should be fine with a gate that short. Only about 1/2 that weight will be applied to the top of the post where bending would be the greatest. The other hinge I suppose is relatively close to the ground, say 12 to 18" up. A deep 3' wide square block of crete is about  more than 4000 lb's ( assuming 1 cubic yard of crete) The size depth and width don't give me any concerns for a 450 lb gate as long as the soil isn't really poor and soft. 6" wide x 1/4" thick square tube should hold up the gate and not bend significantly. If you are really concerned, toss some rebar in it and grout it solid to increase it's resistance to bending.

 

 

My greatest concern would be the hinge attachment points. I've seen a lot of these where a couple things happen. #1 the masons get there 1st and block up the whole thing and you can't get easy direct access to the steel column. That leaves you having to anchor your gate into the masonry block and the steel post will end up doing nothing. That or gate pintles .are just single rods welded to the post and stick out close to 12" to get past the block and any cover material. At that point the hinge is the weak point.

 

I've seen several decent ways to attach the hinges.

 

In some cases they weld a T shaped plate  or box shape to the post with the lower part attaching to the post at an angle for support. The top of the "T" is large enough for them to weld or better yet bolt the hinges to, but small enough to be easily concealed by the masonry. This gives a solid mounting point to transfer loads to the post. Keep in mind though if the post is centered on the block, you might be out 12 to 18" from the post. You also have to remember to keep in mind any cover materials like a stone veneer that might be applied depending on how they do the masonry.

 

The second way requires someone have done a bit of thought originally before the posts went in. In this case the steel post is set at one edge of the masonry, usually flush with the outside face of block, so only the stone veneer covers the post. the rest of the block is "behind" the post usually in the shape of a C roughly. Done this way you only have a short distance to support the gate hinges, usually 2-4" for the veneer thickness. If they do split faced block, the mason has to notch every block to fit around the post and with solid block that's usually a real pain for the mason. Given a chance, he'll use full block to make his job easier.

 

Last way I've seen done is that they leave the steel post showing and but the masonry up to it. In this case you have a finished edge showing and you metal connections need to be cleaner. In this case however the block work won't matter at all as long as it's set back far enough to be out of your way.

 

 

If you can, try and set the hinges to the posts prior to the mason working and let him work to your stuff vs the other way around. Leave yourself some adjustment if possible. I know a bunch of gate guys like to use the hinges where they can crank in or out the hinges to adjust the gate for level even if the post isn't plumb. If using fixed welded hinges, you'll have to shim possibly to do so. Keep in mind masons don't always set their work straight and plumb. You may end up with a tilted surface you are working to or a very irregular one. Know in advance what they are going to do if possible so you can avoid trying to reengineer the wheel after someone else made their job easy at your expense... I've seen guys set things up for say a 10 foot opening as marked on prints only to find the mason did whatever he wanted and the opening is suddenly say 8'-10 or some goofy number so the mason could work with full block and save time. All of a sudden the pattern that looked great on the 10 foot gate won't work any more...

[Blackwaterforge]

 

Last way I've seen done is that they leave the steel post showing and but the masonry up to it. In this case you have a finished edge showing and you metal connections need to be cleaner. In this case however the block work won't matter at all as long as it's set back far enough to be out of your way.

 

 

 

Thank you for your reply!

Post will be flush on face side with masonry.

[ThomasPowers]

What's the soil like?  What's the climate like?  If the post is flush, masonry is not going to do much to affect rigidty.  Will the post be filled with concrete?  (and rust proofed inside and out!)

 

Is the gate designed with a diagonal to take up sag?

[Blackwaterforge]

Soil is clay.

Climate is southern.

Post is in center of 30" concrete.

Post not filled.

Customer wanted gate and post unfinished.

Gate is 2" square tube with 3/4 round every 6" horizontal and diagonal.

 

It will basically be a larger version of these indoor gates.

 

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[Jim Coke]

Greetings Blackwater,

 

I have learned from experience that it is best to always always make provisions for adjustable hinges.. Yep they will sag and that's a fact..   450 is a lot of weight at 7 feet...

 

I hope this helps

 

Forge on and make beautiful things

Jim

[Steve Sells]

Even something as simple as a turnbuckel and guy wire for a diag will help in the long term.

[Judson Yaggy]

I'll buy you a beer (or carbonated beverage of choice) if a contractor you don't know has set two steel posts a specific distance apart to plumb, the same elevation, and aligned along the same line perpendicular to the center of the driveway.  What rust prevention measures were taken where the steel meets concrete or goes below grade?  If structural steel or masonry looks shabby or fails in 10  years will it affect your reputation?

 

A very careful site survey is a must.

 

There are contractors that work to very tight standards out there, I hope you have found one, chances are they work for wealthy clients.  Price your work accordingly.  If the steel has been installed less than perfectly then you will need to make hinges that take that into account and probably fix someone else's short cuts, which will also be very expensive.  Top quality ironwork takes a lot of time from design, forging, fabrication, finishing, to installation.  All of those steps cost real money.  Fixing or designing around someone else's medium quality work also costs money.  In the high end world your reputation is more important than "getting it done".  

 

Your specific question is an engineering problem.  Calculate center of mass of one leaf of the gate.  Bring that info to an engineer along with column size, footing size and depth, soil type and compaction, and hinge elevations, and he will tell you that everything needs to be 3 times the size you thought it would be (grin).  

[Jon Smith]

I'll buy you a beer (or carbonated beverage of choice) if a contractor you don't know has set two steel posts a specific distance apart to plumb, the same elevation, and aligned along the same line perpendicular to the center of the driveway. What rust prevention measures were taken where the steel meets concrete or goes below grade? If structural steel or masonry looks shabby or fails in 10 years will it affect your reputation?

A very careful site survey is a must.

There are contractors that work to very tight standards out there, I hope you have found one, chances are they work for wealthy clients. Price your work accordingly. If the steel has been installed less than perfectly then you will need to make hinges that take that into account and probably fix someone else's short cuts, which will also be very expensive. Top quality ironwork takes a lot of time from design, forging, fabrication, finishing, to installation. All of those steps cost real money. Fixing or designing around someone else's medium quality work also costs money. In the high end world your reputation is more important than "getting it done".

Your specific question is an engineering problem. Calculate center of mass of one leaf of the gate. Bring that info to an engineer along with column size, footing size and depth, soil type and compaction, and hinge elevations, and he will tell you that everything needs to be 3 times the size you thought it would be (grin).

As an engineering student, always allow 5% margin of error extra.
As someone who has had to work around others' mistakes, 3x might not be a bad idea....

[Charles R. Stevens]

If the post tilts under the gates weight it will be direction the gate hangs in most often. You can compensate by making your footing run toured or away from the direction of force. If you make your footing exetric, even "L" shaped it will resist the side lode better. If you put the mass below grade, and opposite the load, the gate must not only lift the mass, but the soil as well. I really like bronze bushings, thrust washers and grease zercs. As well as hardened rat tail pins for hinges, no squeaks and they will out live you.
If the gate is not automatic, you may consider using a stop for the end of the gate to set on in the open position.
As to hinge placement, as far apart as practical, with the bottom as low as possible. Infact if the hinge side vertical of the gate is used as a hinge pin ( setting the vertical in a socket set in the ground, and extending the upper pivot point from the post to the top of the vertical element. Is much stronger. It may not be as appealing to your customer tho.
I hope my rambling makes sense.

[Blackwaterforge]

Thanks guys!

Gate post are plum.

Contractor used a transit for level.

They have 1.5 yards of concrete per hole.

Contractor said ground was firm.

[DSW]

Gate post are plum.

Contractor used a transit for level.

 

 

 

Their "plumb" and mine don't always match up.... I worked one job where the masons "plumb" walls ended up tapering in enough in 10 feet that they actually shortened up the basement by just over a foot. One wall tilted in about 8" in 10 feet

 

 

Same goes for the use of a transit. We got a call back on one job because the carpenters claimed we'd screwed up the level on the tops of the walls we poured. Ok, Our laser is supposed to be +/- 1/64" at 1000', so maybe the laser got dropped and was out of alignment. Off it went to be calibrated and verified, and we borrowed a certified one from the repair place to check our work... Turns out our stuff was with in +/- less than an 1/8" max vs the 2 1/2" the carpenter claimed. This ended up backed up by the surveyors who had also shot the walls for setting the steel. Turned out we later found out he'd used a manual transit and they must not have leveled it correctly. Thus THEY unleveled the building by 2 1/2".

 

I've also run into issues with "level" any number of times when I was helping set Xray machines with a friend. Most guys figure as long as the bubble is within the lines, it's "plumb" or "level".  Bzzzt! Wrong answer!

 

Verify things for yourself, and make plans in advance for things NOT to be level and plumb.

[Charles R. Stevens]

Get the feeling that we are all to familiar with Harold's law?
Harold's law states " Murphy was an optimist"

[Dodge]

Their "plumb" and mine don't always match up.... I worked one job where the masons "plumb" walls ended up tapering in enough in 10 feet that they actually shortened up the basement by just over a foot. One wall tilted in about 8" in 10 feet

 

 

Same goes for the use of a transit. We got a call back on one job because the carpenters claimed we'd screwed up the level on the tops of the walls we poured. Ok, Our laser is supposed to be +/- 1/64" at 1000', so maybe the laser got dropped and was out of alignment. Off it went to be calibrated and verified, and we borrowed a certified one from the repair place to check our work... Turns out our stuff was with in +/- less than an 1/8" max vs the 2 1/2" the carpenter claimed. This ended up backed up by the surveyors who had also shot the walls for setting the steel. Turned out we later found out he'd used a manual transit and they must not have leveled it correctly. Thus THEY unleveled the building by 2 1/2".

 

I've also run into issues with "level" any number of times when I was helping set Xray machines with a friend. Most guys figure as long as the bubble is within the lines, it's "plumb" or "level".  Bzzzt! Wrong answer!

 

Verify things for yourself, and make plans in advance for things NOT to be level and plumb.

 

Agreed. I make it a habit to check level of anything that is plumb critical regardless of what they claim. It may have been set dead nuts 2, 3, 5+ years ago or even yesterday, but stuff settles. That kinda stuff has the same "Oh DARN-it" factor as the "I cut it three times and its still too short" category.

[Judson Yaggy]

Thanks guys!

Gate post are plum.

Contractor used a transit for level.

They have 1.5 yards of concrete per hole.

Contractor said ground was firm.

This is a good STARTING point if you know and trust the contractor.  A site visit and detailed survey is a must regardless. Anyone who has done this professionally will have stories like the guys above have related, I hope this isn't where you get your "I lost so much money" story.  

 

Don't forget to check plumb on both sides of the post;  what will hold the gates in an open position.  

[ironwolfforgeca]

you all wreck my day I have enough problems with  Murphy NOW you tell me theirs a Howards Law :(  :(  :( 

gonna have to tell you about Sewer Sonoids sp ?  then there the invisible little buggers that hide everything from you LOL !!!!!!

wheres that wench I just put down ??? on the table  :wacko:  found this out when we started working on cars here years ago OUCH !