# Avoiding Sagging-Design Critique



## WoodHoarder (Feb 26, 2012)

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.


----------



## Redoak49 (Dec 15, 2012)

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.


----------



## AandCstyle (Mar 21, 2012)

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?


----------



## MrUnix (May 18, 2012)

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


----------



## clin (Sep 3, 2015)

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 (Sep 3, 2015)

> 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:
> 
> ...


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.


----------



## MrUnix (May 18, 2012)

> 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


----------



## devann (Jan 11, 2011)

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.


----------



## rwe2156 (May 7, 2014)

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…...


----------



## Lazyman (Aug 8, 2014)

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.


----------



## WoodHoarder (Feb 26, 2012)

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.


----------



## Smitty_Cabinetshop (Mar 26, 2011)

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!


----------



## DirtyMike (Dec 6, 2015)

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.


----------



## JBrow (Nov 18, 2015)

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.


----------



## DirtyMike (Dec 6, 2015)

great mind think a like huh, jbrow,


----------



## WoodHoarder (Feb 26, 2012)

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:


----------



## Lazyman (Aug 8, 2014)

They might help for a while but I think they are too small. If you think about it they are really just small versions of the diagonals that were recommended above. The stress really needs to be transfered to top corner on the hinge side and they do that on a small scale but the weight away from the hinge side will have so much leverage it will eventually fail probably by pulling out the screws holding to the wood. Now if you joined the 4 corners in a welded rectangular frame it might accomplish the same thing without the diagonal. My theory anyway.


----------



## clin (Sep 3, 2015)

It's not a question of preventing sagging, it's a question of how much. Adding these braces will make it more rigid. But given the size of your wood and the M&T joints, I don't think they would add that much. Would it just happen to be the difference between too much sag or not, possibly, but not likely.

If the braces were much larger, to the point that the diagonals touch across the shorter horizontal span, and the metal itself is thick enough or something like square tubing, then I think you'd have something that would ensure insignificant sagging.

Have you already cut the groove, for the panel boards, in the frame pieces? If so, I inderstand you said you have 3/4" space to add support, wood or metal, and still not go past the frame. But, if you haven't cut that panel groove yet, you can offset it. That would allow you to add more substantial diagonal support.

Myself, I'd go with the very common wood diagonals. I think that would look better than metal ones that are large enough to really help.

But some 3/4" square tubing as the diagonals, made as large as possible, painted black would look okay.


----------



## JBrow (Nov 18, 2015)

WoodHoarder,

I personally think the metal corner bracing would detract from the gates' appearance and, while offering some support, perhaps not enough.

After thinking about this problem and re-reading clin's first reply, I would think adding a single cedar diagonal within each of the four lower frames would provide the support required. My reading of clin's suggestion is that cedar in-fill planks would be applied to the diagonal brace, leaving the diagonal brace proud of the in-fill planks on one side of the gate while the diagonal would not be visible from the other side of the gate. An alternative is to install diagonals that are set flush with the rails and stiles of lower frames and thus integrating the diagonals within the frame.

This alternative approach would use cedar diagonals that are the perhaps the same width (or possibly narrower) but the same thickness as the rails and stiles. The diagonals would be grooved along both edges to accept the cedar in-fill planks that will make up the center panels. The diagonals would be let into the frame corners at the stiles. The diagonal/stile joint could be a mortise and tenon or half-lap joint leaving the diagonal faces flush with the rails and stiles of the frame. The diagonal's joint to the stiles could be reinforced with dowels. The in-fill planks would be square cut at one end and mitre cut at the other end and slipped into the rail and diagonal grooves. Keeping the diagonal joinery on the stiles only would allow for partial assembly of the gate as the cedar in-file planks are installed.

While this approach would greatly strengthen the gate, it would change its appearance. The change in appearance would however be consistent with the overall look and would avoid the appearance of after-thought fixes that could be evoked by adding metal hardware.


----------



## kelvancra (May 4, 2010)

I've monkeyed with more than one sagging gate for customers and I'm a huge fan of cable and crimps.

I didn't care for the visible metal supports, so I drilled holes through the wood on the same diagonal line the cable ran, then drilled a second hole to bring the cable back to itself. Once it was doubled back on itself, crimped it.

The turnbuckle was a must, to allow future adjustments. After all, it's not "if the gate is going to sag," but "how much."

I think you will find a pretty small cable will do the job and not, noticeably, detract from your very nice design and work.

Another option depends on the environment of the gates. For example. If the gates will be over concrete, no consideration for diagonal bracing may be necessary, if you have spring loaded wheels, adjustable wheels at the outer points.

Years ago, I rebuilt a major deck for a couple. The ground had settled and likely would some more. As such, I drilled one inch holes in the bottoms of the 4x's and put one inch all thread in the holes. About six inches of the all-thread went into concrete. A washer and nut at the ground and one at the post allowed future adjustments.

This concept could be applied using casters too.


----------



## Tony_S (Dec 16, 2009)

This.
http://lumberjocks.com/projects/90129

Cross/half lap the diagonal into the center stile.
The only change I would make, is to notch the diagonal into the hinge side stile vs. hinge side rail.

As long as you fit it all properly, it'll be solid as a rock….and look good.


----------



## WoodHoarder (Feb 26, 2012)

Hello All,

This gate had been on the back burner for quite some time and I need to get it completed. The last step before finishing is the diagonal bracing. By the time I had posted, I had already cut the slots in the center for he vertical boards. My plan moving forward, having considered all the great advice, is to run a 3/4" diagonal board behind the vertical panel boards making it flush with the outside rails. My only holdup is how to deal with the bracing crossing the center rail.

I think I have two options.
1) Cut a 3/4"channel out of the center rail where the diagonal crosses.
2) Cut the diagonal into two pieces and run them directly into the center rail with small tenons. (please see picture)









I prefer option 2 as I feel it makes for a better look.

My question is: Do you think doing this way and effectively splitting the board will negate the effect of the diagonal bracing?

Thanks again for all your great advice.


----------



## JBrow (Nov 18, 2015)

WoodHoarder,

Option 2 creates stress on 4 joints whereas Option 1 limits stress to 2 joints. Therefore, I would think Option 1 is a safer option plus Option 1 may resist a twisting or wobble as the gate is opened and closed a little better than Option 2. But if the 4 joints are designed and fitted to handle the stresses, it would probably work ok.

Several years ago I constructed a picket style fence that included a 50" wide gate with a single diagonal brace from ¾" final thickness red oak. I approached the diagonal bracing problem per Option 1 with half lap joints. Tedious to layout and cut for sure, but somehow I managed tight fitting joints and it has held up well. Although unnecessary based on my experience, were I to build that gate today, I probably would have pinned the ends of the diagonal brace with some dowels. In any event, the gate remains square and structurally sound.

I am not sure it matters that much, but I would think that the diagonal brace attached to the upper end of the hinge side stile and to the opposite corner bottom rail might provide a little more support.

For whatever its worth, I posted a photo of the red oak gate.


----------



## clin (Sep 3, 2015)

There's not some extra strength property running one diagonal. I would run two, full-length diagonals. Both going in the same direction to be under compression. Each half will resit racking and therefore the entire structure will resist racking (sagging).

I would also consider running screws through the diagonal into the vertical panel boards. This will help stiffen the diagonal and give it more resistance to bending. If you put a single screw where the center of the diagonal crosses the center of a each panel board, wood movement shouldn't be an issue. Use brass screws or stainless steel. But brass looks quite nice and I don't think would detract from the look.

If your final look is heavy duty with large bolts, like a castle gate, then of course you could use similar hardware for matching accents.

Also, I would run the diagonals into the corners so the center line of the diagonal hits the corner and rests against both the rail and stile. Since you are using M&T joints these corners are very strong. While as you have drawn it, the joint where the diagonal attaches has to be done in a way it cannot slip or give. But if you tuck the diagonal into the corner, that joint is under compression and only needs to be strong enough to make sure the diagonal doesn't pop out completely. A biscuit or two, pocket screw etc is all that would be needed then. Heck, if screwed to the panel boards, that alone would keep the diagonal in position with nothing else securing the end of it.

It's a bit more work cutting the two angles in the end of the diagonal, but it's not that hard and clearly with your skill level this is not an issue.


----------



## Lazyman (Aug 8, 2014)

As drawn, those tenons are pretty short. Not sure that will give you enough mechanical strength to be of much use. One reason to use tenons, in general, is to add glue surface and it just won't have much surface to provide any advantage. With such short tenons it is practically a butt joint. This might be fine if it is in compression but not in tension. Personally I like option one better and I think that a well executed diagonal lap joint might actually add to the look (as JBrow's example shows). I would also make the tenons on the ends longer as well and it might not hurt to pin them with dowels or screws.

My 2 cents.


----------

