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Avoiding Sagging-Design Critique

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Forum topic by WoodHoarder posted 06-26-2016 09:02 PM 841 views 1 time favorited 24 replies Add to Favorites Watch
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WoodHoarder

66 posts in 1746 days


06-26-2016 09:02 PM

Topic tags/keywords: driveway gate cedar gate

Hello All,

I have been working on a cedar driveway gate the past several months. I currently have an 8 part series on the build in the blog section.

On my last section a kind lumberjock expressed concern that a lack of diagonal bracing could lead to sagging over the years. Given the time and expenses I have put into this, I want to make sure that I designed it correctly.

When designing the gate, I put a vertical upright in the middle of the frame. The joints are mortise and tenon and will have two drawbore pins in each joint. (total of 8 joints per gate). Furthermore, the open portion below the arch will have a steel frame with decorative swirls. (extra weight and possibly rigidness)

I felt this would be sufficient to create enough rigidness to prevent sagging. I am now doubting my design.

Any thoughts and suggestions would be appreciated.

-- Christ was a carpenter...a fact that humbles and inspires me.


24 replies so far

View Redoak49's profile

Redoak49

1951 posts in 1454 days


#1 posted 06-26-2016 09:14 PM

It looks well designed and made. But I think you will have some sag. The forces on it will want to pull the middle down and wood will compress slightly at the joints letting it sag somewhat. I would want a diagonal element going from the bottom outside to the middle up high. Alternatively, some kind of cable running from the top outside to the bottom middle.

Really nice job but think there will be some sag.

View AandCstyle's profile

AandCstyle

2572 posts in 1722 days


#2 posted 06-26-2016 09:28 PM

Wood, aside from the potential sag concerns mentioned, your posts might sag as well unless they are extremely well anchored and rigid. Those look to be heavy gates and then there is the wind load to consider. Have you considered putting small wheels on the bottoms of the center posts?

-- Art

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MrUnix

4230 posts in 1664 days


#3 posted 06-26-2016 09:31 PM

If you don’t have a diagonal brace, it will sag… pretty much not if, but when. On all of the wooden gates I’ve made that didn’t incorporate a built in diagonal, I always add steel cables with turnbuckles for adjustment. They work great as long as you install them properly. Put them on the inside (ugly side :) and from a distance, they are basically invisible.

You can fabricate it up yourself, or get something like this kit which basically has everything you should need:

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View clin's profile

clin

514 posts in 461 days


#4 posted 06-26-2016 10:13 PM

I’m currently in the design phase of some much smaller yard gates. But my intent was to build them similar to yours. Keep in mind that this is pretty much the same as a traditional wood door with a floating panel. But obviously being wider there is a larger moment (leverage) trying to pull the gate down.

No question a diagonal could help to ensure little sag. Is it really needed? I’m sort of a belt and suspenders guy.

The steel work could help, but ONLY if you put gussets (diagonals) at the corners or some other diagonal element. If it is just a simple frame with vertical bars (for decoration) it will just add weight and no resistance to racking

Looking at your blog, your design calls for vertical panel boards. I think if you ran diagonals on the inside of the gate, behind the panels boards, it would of course not change the look of the gate on the “good” side, but I don’t think it would detract on the other side. You clearly would do it well.

I see no reason the diagonal couldn’t be flush with the frame, so that means the diagonal can be as thick as the space between the panel boards and the frame. I have seen designs where the panels boards are NOT centered in the frame. This allows the diagonal to be thicker.

Wood diagonals have value regardless of the direction, but are typically put in compression. If the diagonal is thick, it will hold compression and runs from the lower hinge side to upper latch side. But if the diagonal is thin, it may be better used in tension. But this requires that it be joined securely to the frame.

You could attach the diagonal to the vertical panel boards, that will tie it all together. But, as always, you don’t want to bind those panels boards else you my cause splitting.

Since you are putting steel in the design, another option is a flat, steel bar running diagonally to carry tension. Perhaps even attached to a wood diagonal. Might be able to tie it in nicely to the other steel work.

Found these guys in the UK. I think they use diagonals on most of the gates. Hard to say, they don’t have as many photos of the backs. But it certainly makes it clear you’d be in good company adding diagonals.

http://woodengatemakers.co.uk/bespoke-gates

-- Clin

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clin

514 posts in 461 days


#5 posted 06-26-2016 11:27 PM


If you don t have a diagonal brace, it will sag… pretty much not if, but when. On all of the wooden gates I ve made that didn t incorporate a built in diagonal, I always add steel cables with turnbuckles for adjustment. They work great as long as you install them properly. Put them on the inside (ugly side :) and from a distance, they are basically invisible.

You can fabricate it up yourself, or get something like this kit which basically has everything you should need:

Cheers,
Brad

- MrUnix

The problem with cables attached with that sort of hardware is it puts the cable on the very outside surface. The tension pulls the gate out of shape. Making it sort of a potato chip. I also happen to think they’re ugly. Necessary sometimes, but ugly.

Woodhoarder’s gate is a fine piece of woodworking, and I wouldn’t put a cable on it.

I have used cable on new gates, but I centered it in the width of the frame. In that case, the gate used pickets attached to the outside of the frame. With WoodHoarder’s design that’s not possible.

-- Clin

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MrUnix

4230 posts in 1664 days


#6 posted 06-26-2016 11:31 PM

The problem with cables attached with that sort of hardware is it puts the cable on the very outside surface.

Notice the part I mentioned regarding “They work great as long as you install them properly.” ;-)

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

View devann's profile

devann

2201 posts in 2158 days


#7 posted 06-27-2016 07:39 AM

WoodHoarder, When building doors or gates unless it is constructed has a shear panel, diagonal bracing will be required to minimize sagging. In all applications where a solid ( not a cable) diagonal brace is used I configure it so that the downward compression caused by gravity is transferred to the lowest hinge used to secure the door/gate. In the case of gate building this places the greatest part of the load lower on the gatepost minimizing the stress put upon the gatepost. If you’re bracing up to the top hinge you’re hanging more weight higher on the gatepost. Thus causing more stress on the gatepost by raising the center of gravity on the gatepost where the weight will bear.

For your project I would continue has planned with the steel frames using them to transfer the load to the lower outside corners of the gates.

btw, the hinges will be the “weakest link in the chain” I would use no less that four per gate, possibly five.

Those are some nice looking gates you’re building.

-- Darrell, making more sawdust than I know what to do with

View rwe2156's profile

rwe2156

2198 posts in 946 days


#8 posted 06-27-2016 01:03 PM

Will it have solid panels or boards? How will they be attached?

Very well constructed with the draw bore pins, but when weather gets to it, you never know what will happen.

You can always go back later and add a brace or stay.
Obviously very stout hinge posts in concrete…...

-- Everything is a prototype thats why its one of a kind!!

View Lazyman's profile

Lazyman

695 posts in 852 days


#9 posted 06-27-2016 01:41 PM

Brad’s (MrUnix) approach is probably the best idea but that may detract from the aesthetic you are going for. Perhaps you could run the cables or a steel rods in such a way that the vertical boards you going to use to fill the areas between the verticals to sandwich the cable or rods and hide the supports (2 layers in stead of 1). You will have to drill a hole in the center vertical of each side for the cable or rod to go through but that should not hurt the strength any.

Another thing to think about is to somehow incorporate or at least hide the diagonal support into the iron work you are planning for the top? If you can for example run the diagonal from the top to the middle cross beam, you essentially make a boom that the bottom 3/4 of the gate hangs from.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View WoodHoarder's profile

WoodHoarder

66 posts in 1746 days


#10 posted 06-28-2016 05:44 PM

Wow, thanks for all the input and suggestions. I really do appreciate it.

I’ve been slowly considering each of the suggestions and still trying to wrap my mind around the best way to deal with the issue (although everyone’s input has helped with the clarity). This gate has certainly tested my sanity at this point. I certainly agree that some sort of diagonal bracing is needed and the load on the posts needs to be considered.

BTW, I plan to anchor one side to the house and one side to a block wall. The tongue and groove panels will be floating in a groove in the center. This will leave roughly 3/4 inch between the face of the panel and outside of the frame on both sides. I’m also not as concerned about how the back of the gate looks as it facing the yard. The intention really is to improve the look of the house…and having the coolest gate in the neighborhood ;-).

I have also considered fabricating something like a cradle out of angle iron that will be welded to the hinges and completely support the gate from the bottom….not sure how well I described that. I’ll need to draw it out in sketchup and see what you guys think.

Thanks again for all the help. I’ll be referring back to here often as there are so many good suggestions.

-- Christ was a carpenter...a fact that humbles and inspires me.

View Smitty_Cabinetshop's profile (online now)

Smitty_Cabinetshop

13735 posts in 2083 days


#11 posted 06-28-2016 06:40 PM

I’m not building a gate, but have hinged doors on a couple of outbuildings. I really like Clin’s observation:

Wood diagonals have value regardless of the direction, but are typically put in compression. If the diagonal is thick, it will hold compression and runs from the lower hinge side to upper latch side.

It makes the most sense to me, running diagonals up, towards the latch, from the low hinge corner.

Good post, great replies, nice gate, WoodHoarder!

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

View DirtyMike's profile

DirtyMike

461 posts in 367 days


#12 posted 06-28-2016 07:07 PM

I fully agree with with smitty and brad . I have built many wooden gates for driveways,backyards,etc. Seems without some diagonal support sagging is going to happen. the cable kits above work great but could be and eye soar for a gate as nice as yours. I recommend 4 gauge solid copper wire and make your own turnbuckles using and eye bolt and a recessed nut and washer. Gate looks great by the way, it wouldn’t have looked as good with wooden diagonal supports imo.

View JBrow's profile

JBrow

818 posts in 385 days


#13 posted 06-29-2016 02:10 AM

WoodHoarder,

The zinc plated, galvanized, or stainless hooks, cable and turnbuckle solution would really detract from the gate. But if this ends up being your best option, considering nautical hardware made from brass or bronze and some heavy gauge bare copper grounding wire would, to my eye, look way better and perhaps even compliment the gates; which by the way look pretty nice.

View DirtyMike's profile

DirtyMike

461 posts in 367 days


#14 posted 06-29-2016 02:16 AM

great mind think a like huh, jbrow,

View WoodHoarder's profile

WoodHoarder

66 posts in 1746 days


#15 posted 07-03-2016 01:34 AM

What do you guys think of this idea:

I was shopping at Home Depot and came across some small steel diagonals. How about placing them on the back (‘ugly’) side of the gate, one in each corner. Do you think this will add to the rigidness enough to prevent sagging?

Here are some examples, I’d likely fabricate my own:

-- Christ was a carpenter...a fact that humbles and inspires me.

showing 1 through 15 of 24 replies

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