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Cantilevered Pergola/Lean To Privacy Fence

by Biddles
posted 06-28-2020 08:29 PM


24 replies so far

View Craftsman on the lake's profile

Craftsman on the lake

3468 posts in 4294 days


#1 posted 06-28-2020 08:48 PM

I’d notch and bolt the wood on the rear beams. Wouldn’t be too much difficulty to do it. The bolts alone might hold but it’s not the recommended way to put beams together.

That being said, if you’re in NY did you consider the snow load on that roof? I live in Maine and have built covered pergolas (with four legs) and still I sweat it.

You could place bolted on Supports on the front ends of the roof, installed in the fall before the snow arrives.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View CWWoodworking's profile

CWWoodworking

1030 posts in 1035 days


#2 posted 06-28-2020 09:53 PM

The first pic looks destined to fail. Especially if you put a roof on it.

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tmasondarnell

138 posts in 2645 days


#3 posted 06-29-2020 12:39 AM

Best practice (and in many places code) is to notch the beams or to used an engineered hanger.

I would definitely notch the beams. I may be a bit of a belt and suspenders man when it comes to construction, but I am a firm believer that fasteners should one fasten and near carry a load. I always want the load to be carried by the actual structural members.

I am a little concerned about the depth of your posts and the possible sheer force on that roof. You are essentially building a giant sail. Are the beams going to be fastened to the deck for additional lateral stability?

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Biddles

27 posts in 1271 days


#4 posted 06-29-2020 02:58 AM

I did not plan on fastening the posts to the deck, but Im not completely ruling it out. I would prefer this structure supported itself. I was planning on notching in lower lateral support, and notching in the upper lateral support beam. The roof angle will be sloped, not flat, just not as steep as the second pictures angle. But this is why I’m here, to get some advice on building this strong enough that I can sleep at night without worries.

View CWWoodworking's profile

CWWoodworking

1030 posts in 1035 days


#5 posted 06-29-2020 03:16 AM

Notch it and make a steel plate to go over the joint. Repaint the plate as needed to keep from rusting. Or use stainless. This may get you some years of use, but it will probably still fail.

History tells us unsupported, not Trussed wood structures measuring 8’ out don’t fare well. There simply aren’t any that are old.

Here’s an idea. Instead of a wood structure, have a metal fabricator(you if your inclined) do some cool cantilever design for the overhang. Then sew some out door fabric for the shade part. Design it so you can take it down/replace as needed.

Provides shade, last forever, change colors as fashion changes, keeps leaves out.

Good luck.

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Woodknack

13475 posts in 3236 days


#6 posted 06-29-2020 04:29 AM

I thought of building something like pic2 but we have hurricanes and there is no way to build it strong enough to survive that on a homeowner budget, at least not my budget. For the roof you might consider retractable canopies that can be pulled back in winter or during wind storms.

-- Rick M, http://thewoodknack.blogspot.com/

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Craftsman on the lake

3468 posts in 4294 days


#7 posted 06-29-2020 11:47 AM

Again. Bluntly
With a possible snow load

Picture one with a roof NO…
Picrture two with a roof, YES but Posts go underneath or notched. Bolting on the sides to hold weight is not good and in Maine at least, not legal for roofs or decks.

Snow weighs up to 20 lbs per cubic foot. If the roof were 10×10’ and the snow 2 ft thick which shouldn’t be that unusual anyplace in NY especially north and west NY, then that’s 4000 lbs. So, you need to build the roof to take at least but possibly in excess of 2 tons. (3 ft of show? = 6000 lbs)
Also, I have steel roofs here in Maine on my house, garage, etc. On a 5/12 pitch roof the snow slides off, after awhile, but on anything much less than that it stays, especially after the roof gets dirty. I braced the hell out of my hip roofs here on the house for just that reason. And, even on that 4ft of snow one winter, which is unusual, I took two feet off.

The cross bracing on the first picture is strong. The cross bracing on the second picture isn’t made to hold a load.

So it would be the first picture with front legs as in the second picture. If you didn’t want a roof, or had a removable one then the first picture would be fine as is.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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Biddles

27 posts in 1271 days


#8 posted 06-29-2020 08:44 PM

I guess I need to go back to the drawing board. I can’t have 6×6 posts going through the deck to support the front of the roof without it looking completely out of place. When I step out of the sliding glass door from the kitchen onto the deck the hot tub is two feet to the right, so I can’t have a support post sitting right there. It’s just out of place.

I know I can build a privacy fence onto the edge of the deck, that shouldn’t be a problem, but then I really need to figure out a roofing solution to get shade, and cover the hot tub from the sap, and elements.

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HerringImpaired

80 posts in 565 days


#9 posted 06-29-2020 09:39 PM

Something like this would cover all but the area for grilling. Just throwing it out there for your viewing pleasure… ☺
I like how the privacy screens roll up and down with the cover as it opens up…. I built a Gazebo of Cedar and Suntuf, but I may have gone this route if I knew it existed….

http://www.covana.com/hot-tub-cover-oasis

-- "My greatest fear is that upon my demise, my wife will sell my tools for what I said I paid for them."

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Craftsman on the lake

3468 posts in 4294 days


#10 posted 06-29-2020 10:55 PM

Other possible options depending on the amount of room you’ve got.

Put more corner posts but put them back a bit, maybe 25% back from the front.

Put a beam across the front and put one center post or two posts separated but towards the center front.

Another good reason for not having just two rear posts and lots of snow. The snow on the front end of the roof will place a ton of pressure on the front. The rear posts, unless they were anchored deep in the ground with cement would break at the base. Especially if you just bolted them to the deck at the base. I think it would pull your deck up off the ground at that point with a lot of snow if the roof didn’t break first.

I have seen draped cloth on these things as a sun shield. Removed in the winter. Wouldn’t need big supports on the top either.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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Biddles

27 posts in 1271 days


#11 posted 07-01-2020 10:02 AM

Maybe I can do it without the roof, and run some eye hooks to put on a fabric top, but the sap from the pine tree would likely ruin it. Gotta rethink this, because I really want to prevent the hot tub from the daily elements, and protect it from the sap. Maybe in the winter I can just use three support posts on the deck to support it, but for the rest of the year it should hold fine right? It’s just the snow load we’re worried about here?

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CWWoodworking

1030 posts in 1035 days


#12 posted 07-01-2020 10:15 AM

Post a pic of your space

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Craftsman on the lake

3468 posts in 4294 days


#13 posted 07-01-2020 11:59 AM

You have a cantilever and Y braces to hold the roof from breaking off or sagging. The braces seem necessary at that point right? But, what braces the bottom of the posts? The pressure is the same down there. If the posts are in the ground and cemented in maybe. But if you have maybe a 2×10 with a couple of bolts at the base of the posts holding an entire overhanging structure of wood with no corn braces at that point, then would that be the same as if you had just bolted the roof the posts without even any braces?

Not trying to be difficult here. I’ve built a lot of decks and even some with sunroofs on them and if I did this I’d just be keeping my fingers crossed and have to tell the people (mostly relatives so it’s okay) keep your fingers crossed because I’m just not sure what will happen here. I’d be saying, “during the winter don’t let the kids play under this thing.”

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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Biddles

27 posts in 1271 days


#14 posted 07-02-2020 12:21 AM

I was planning on using 3’ ft cement piers with these post bases to hold the 6×6 posts. Like this.

I’ll try and get a pic tomorrow, although I don’t see it helping much as the deck isn’t in, but you can get a better idea I suppose.

I could put the posts into the concrete themselves, just not sure how deep they would need to sit, and how much concrete I would need around them to be deemed safe. Also how would I prevent it from being pulled upward? Just put a large 8-10” bolt through the base before concrete?

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Craftsman on the lake

3468 posts in 4294 days


#15 posted 07-02-2020 12:33 AM

Embedding it deeply in concrete maybe. The metal hold fasts you show won’t rally cut it. They’re made to keep a post in place latterally, not rally connect them much to the concrete. The connection to the wood wood by screws is the weak point.
If you were to put an 8 foot 4×4 connected to one of these you could grab the top and pull it off by hand.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View Lazyman's profile

Lazyman

5826 posts in 2243 days


#16 posted 07-02-2020 03:32 AM

I am no engineer (you probably need one) but I am pretty sure that the posts need to be at least 3’ ( probably more depending upon height and size of the overhang) in the ground, not just attached to the top of 3’ piers. With support only on one side, there is nothing that would prevent it from just falling over if the posts are not in the ground. The support on the back looks like it is attached to the back side of the posts. They are normally in tension to counteract the weight on the front and I would think it needs to be attached pretty securely, but they will do nothing to prevent the posts from falling over if they are not buried deep into the ground. Those back supports will help keep the joints from pivoting like a hinge but they do nothing to support the weight of the overhang or prevent it from falling forward or even backward in a high wind.

Here is a plan for similarly designed cantilevered roof. As you can see in the diagram, they have the posts way in the ground.

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

View Redoak49's profile

Redoak49

4880 posts in 2844 days


#17 posted 07-02-2020 11:01 AM

The use of those post based is a not good idea and it would quickly fail.

You need large posts buried deep in the ground.

View BoilerUp21's profile

BoilerUp21

160 posts in 1623 days


#18 posted 07-02-2020 12:20 PM

I just started the same project. I poured 4’ x 12” diameter concrete footings for the two posts with a J bolt to mount the base plates…I used these post bases:

https://www.lowes.com/pd/Simpson-Strong-Tie-6-in-x-6-in-Triple-Zinc-Wood-to-Concrete-Retrofit-Base/1002709014

For a cantilevered design, these post bases are not the best due to the moment load exerted by the cantelievered weight. To compensate for this, I fabricated and bent (I have a 20 ton shop press with bending die) two additional 1/4 thick x 4” x 8” brackets for the other two faces of each column. Used concrete anchors and then put a total of 8 lag bolts through each post. Very sturdy now, but in hindsight, should have just got 10’ posts, screwed a couple lag bolts in the bottom 6”(for uplift protection), placed them in the form 2’ down and called it a day.

Hopefully my mistake will help you with this design. Those concrete bases from Lowes are not cheap, but would be great for a 4 post design, just not out cantilevered design.

I notched my posts and lag bolted through the top. In addition i ran a 15 degree angle on them to help with the roof load not being as far out and creating less of a moment load on the base connections.

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Craftsman on the lake

3468 posts in 4294 days


#19 posted 07-02-2020 12:42 PM



I just started the same project. I poured 4 x 12” diameter concrete footings for the two posts with a J bolt to mount the base plates…I used these post bases:
- BoilerUp21

This would be okay if you’re not going to put a roof on it that will collect snow or if you’re in a low/non snow area. And your roof isn’t that long.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View squazo's profile

squazo

185 posts in 2501 days


#20 posted 07-02-2020 12:46 PM

your going to have to embed quite a bit of wood into the concrete, I would say something like 5 feet deep, and probably use a 4 ft diameter hole, I would also opt for an 12X12 column so that when you notch for the supports you still have plenty of material left in the column. Or maybe you could use some counter weights to keep it balanced.

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Craftsman on the lake

3468 posts in 4294 days


#21 posted 07-02-2020 12:55 PM



your going to have to embed quite a bit of wood into the concrete, I would say something like 5 feet deep, and probably use a 4 ft diameter hole, I would also opt for an 12X12 column so that when you notch for the supports you still have plenty of material left in the column.

- squazo


That is better but….
And… I live in Maine, we know snow here like many areas of the north do. If he’s in a snow area of NY then even that will be an issue. Considering the 20 lbs/cubic foot of snow possibility think of it as a possible 4000 to up to 6000 lb vehicle resting on the top of it if the roof is about 10’x10’. With that mechanical advantage nothing less than four posts could make for a tense winter.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

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sras

5566 posts in 3985 days


#22 posted 07-02-2020 01:31 PM

Just an FYI – We are working on a roof extension supported by a beam resting on 2 posts (1 on each end). Pure vertical support – no cantilevering.

The local codes required a footing 28” in diameter and 40” deep.

2 posts can definitely work – no question. The question is how big are the posts and how big are the footings. The only way to know that answer is to work with an engineer.

-- Steve - Impatience is Expensive

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Biddles

27 posts in 1271 days


#23 posted 07-02-2020 02:04 PM

Awesome advice as usual. Im glad I posted about it here instead of just going for it and failing miserably. Im going to strongly consider 4 posts, just hotta figure out how to make it work coming out of the deck.

View Bill1974's profile

Bill1974

143 posts in 3841 days


#24 posted 07-02-2020 04:56 PM

I would strongly recommend having an engineer look it over and sign off on the design and getting a building permit (not sure where you are in NY, but there are number of places where not having one end up cost way if you have to get one after starting).

3 foot does not don’t seem deep enough, to get past the frost depth. I would guess each post is going to need about a yard of concrete if not more.

Instead of putting the wood post in concrete I would recommend a metal on and cover it in wood.

I understand the desire of make it all out of wood, but to do it well is probably going to cost more if no steel is used than if some is. Without some steel in the vertical and horizontal members the wood will bend and sag over time if it all cantilevered.

Without a solid roof, the loads go down. Also it’s usually a cooler under a fabric roof than a metal one. Plus a cloth one might give you the ability to see the stars if it’s retractable.

As for dealing with the sap, prune the tree or cut it down.

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