Pergula

[MoKelly]

I want to try to build a pergula in the back yard area of my house. I have never done anything like this myself but see what the folks on here can do so I want to try to do it myself. It's not like we will live in it so I figure what the heck ... lets give it a try. I have my 16 year old son available to help me with the harder work. Other than that, I will do this on my own.

So, I am in the planning stages and here is my plan:

--- The area available is pretty flat and is mulched. So, no need to do any major landscapping work. We plan to leave the area mulched with some planters and pavers.

--- I would like the pergula to measure 12 feet wide and 16 feet long. The beams will span the 12 foot section and the rafters will span the 16 foot section. I plan to have 2 foot overhangs on the rafter side ... so ... the rafters will span 11 feet 1 inch. I plan to have 1-1/2 foot overhang on the beams so they will span 8 feet 1 inch.

--- I will use 4 - 6x6x12 posts buried 4 feet (with 8 feet above ground) with concrete. I will wrap and treat the portion of the post in the ground. I will use pressure treated wood which we will eventually paint white.

--- The beams will be 4 - 2x8x12 boards sandwiched and bolted to the posts.

--- The rafters will be 12 - 2x6x16 boards screwed into the beams every foot. I sort of want to notch each rafter into the beam with a 2 inch notch in the rafter. Not sure if this helps the structure stability or not, but I think it looks a little better.

--- Maybe, depending upon how it looks at this point, we wol use 2x2's across the rafters. That is yet to be determined and, at least to me, isn't a decision we need quite yet.

Also, my wife is toying with the idea of a porch type swing on teh 12 foot side of the pergula. I am niot sure what additional strength needs to be built (if any) to accomodate that desire.

So, that is my plan. Please provide whatever comments you think I need to be successful.

Thanks much.

MoKelly

 

[EddieWalker]

I'm not a fan of wrapping posts in the ground, it just creates a place for water to remain. I would put them in as they are and crown the concrete so water runs away from the post. I've replaced quite a few posts and the rot is always right where the post comes out of the ground where water was able to remain.

I think you are a little light on your beams and rafters. I would go one size larger for each.

The 2x2's will give you a lot of additional shade. They will also keep the tops of the rafters from turning and twisting over time. Instead of notching the rafters, I would use small metal brackets that would sit on top of the beams and attach to the rafters if you need the extra strength. Of course, screwing them down diagonally from both sides gives you a lot of strength already.

You didn't mention diagonal bracing. This is what will keep your structure steady. The bigger you make the bracing, the stronger it will be. 2 feet on the short side would be the minimum. Be sure to go both ways with it since the structure will move in all directions.

Have fun,
Eddie

 

[MoKelly]

Thank you very much. This is what I need.

OK --- I will go with 2x10's for the beams and 2x8's for the rafters. I'll also plan to use the 2x2's on the very top.

I also will incorporate the bracing --- I have to admit I don't fully understand how the bracing works but will do some additional research to understand just so I do it correctly.

I will be on vacation in August to do this project. I hope to have the area measured out, the holes dug and the materials purchased before then so I can get right to it when vacation begins. I will definitely post pictures.

A side benefit to this is seeing how excited by 16 year old is to do the project with me. That is sort of cool.


I will definitely post pictures as we move along.

MoKelly

 

[wjmst]

The pergola I built is similar to yours only I used 6 4x4's as the posts and 2x6's as the beams and rafters. I did not notch them, just used some hurricane type metal straps on each. It has held up well for several years now. No problems. Your structure should be fine.

 

[Zick]

Recent thread about someone who build one for the first time too and had some issues. This might help;
http://www.tractorbynet.com/forums/projects/314958-pergola-wobbly.html?highlight=pergola

 

[EddieWalker]

I also will incorporate the bracing --- I have to admit I don't fully understand how the bracing works but will do some additional research to understand just so I do it correctly.

If you stand a board up on it's end, it will want to fall over. It can handle a huge amount of weight, but it's not able to stand up on it's own. If you put that board into the ground, it's able to stand up on it' own, but the farther up you go, the more it will move around. If you attach it to the ground with a bracket of some kind, it will also stand up on it's own, but move even more then a post in the ground.

The problem with pergola's and gazebos, and any structure without walls is that there isn't anything to create sheer strength to them like done when building a house. The OSB or plywood installed on the side of the framing locks all the studs together and keeps them from falling over the length of the wall. Then the wall going in the other direction does the same so with two walls, you have a structure that will stand on it's own because of the sheething.

With a gazebo, a lot of this strength is created from the railing. It locks the posts together and keeps them upright.

Since a pergola does not normally have a railing, the only thing that you can do to lock the posts together is diagonal bracing at the tops of the posts. The triangle is the only shape that cannot move. Once the three sides are attached to each other, you have the strongest shape possible in a building. This is how trusses are built. The bigger you make the triangle, the more strength you have. There is a point where you can make the triangle stronger then the wood or fasteners, so there is no point in overdoing it. As a general rule of thumb, you will get all the strength available with angle brackets two feet long on the short side. The posts will still have some movement from the ground up to the beginning of the bracing, but it will be minimal. If you where building a tall deck, you would want the bracing to be much bigger to get more strength out of it, but for this, there isn't any measurable advantage to it.

Be sure to attach the bracing to the post and into your beams and rafters in both directions at all four corners. The better you do this, the longer your pergola will last.

Eddie

 

[davrow]

Nice explanation, Eddie. Thanks.

 

[texasjohn]

A philosophical comment.

You say you have never done something like this...thus it might be assumed that you will be acquiring both tools and experience as you proceed.

When doing something for the first time, I always plan to simply get the tools needed...ladders, scaffolding, saws, hammers, drills, bits, ... whatever...there are always temptations to "make do" with existing tools and not spend extra money. That's always proven to be a poor choice for me. If I go ahead and get the tool needed for the project, then it is there next time I have a project. And, it's amazing how soon that next project arrives!!

I think you'll have a great experience with your son...and, trust me, you need him to help with this project...he'll help you get the task done several times faster than if you sought to do it by yourself.... be sure he knows that he's NEEDED on the job and appreciate what he does.