Building Pergola : questions about wood

[mbrittb00]

We are wanting to build a pergola over our existing patio. The construction is simple enough for us to do the work ourselves. However I have some questions about the size and type of wood to use.

The following website shows the general design idea
http://www.doityourself.com/forum/l...47-building-pergola-questions-about-wood.html


The pergola is going to be roughly 13' wide (rafters) by 10' deep (beams). The plan is to attach a ledger board to the house and use 4"x4" posts to support the front end beams (2 sandwiched around the posts). There would be three pairs (3" spaced) of main beams connecting the ledger to the end beams (one pair sandwiched around each post and one pair in the center. Finally the rafters would be on top of the main beams.

I was originally thinking 2"x6" would would be sufficient, but was wondering if 2"x8" would be better, especially for the end beams (13' span).

Also I've read mixed opinions on treated vs untreated wood. Treated wood has the advantage of being more resistant to the elements, but as a result of the treatment process is heaver and needs time to dry before finishing. Untreated would be nicer looking and some think it would be as resilient to elements if sealed and finished (stain). The 3rd options that is generally considered better would be more durable wood like cedar or redwood. Unfortunately I'm not sure where to look for those (Lowe's and Home Depot only carry the pine (treated and untreated).


Thanks in advance for your feedback.

 

[bud16415]

I built mine all from PT and used a red stain on it. I wouldn’t use untreated anyplace outside.

 

[nealtw]

If you build it now with treated wood, it will be dry enough toward the end of summer to stain.
Rough cedar would give a much niicer look and can be found or ordered from a regular lumber yard but it will cost more.

 

[mbrittb00]

Thanks.

"regular lumber yard" : Would this be something like 84 Lumber, or do need to find a more local / less national place.

Also, what about the size of the boards 2"x6" or 2"x8". I'm a little concerned by the 13' span on the front end beam without a support in the middle. Should I add a temporary support during the summer while it dries, or would that even make a difference (this was a suggestion I had seen elsewhere).

 

[Snoonyb]

Use the 2X8.

Here is a resource that can be used to find wholesale as well as retail lumber vendors in you area;http://www.thebluebook.com

While the big boxes do not carry much other than standard material, the special order desk can get you an estimate.

 

[nealtw]

For the beams I would go up to 2x10

 

[mbrittb00]

For the beams I would go up to 2x10

I was planning to use 2"x6" for the rafters and main beams (10' direction), so I'd be a little afraid that 2"x10" for the end beams would stand out a bit. If I added angle braces for the end beams reducing the unsupported span from 13' to 9' (or 8') do you think I could get away with using 2"x8" for the end beams?

 

[Snoonyb]

If your lumber is S4S and you're talking 24" OC, thats only 8 rafters, and you crown the support, 2x8 should be fine.

Keep in mind, there are two other milled surfaces for the lumber, Re=sawn and Rough sawn. Both have a rough texture and are a thicker milled product.

 

[nealtw]

I was planning to use 2"x6" for the rafters and main beams (10' direction), so I'd be a little afraid that 2"x10" for the end beams would stand out a bit. If I added angle braces for the end beams reducing the unsupported span from 13' to 9' (or 8') do you think I could get away with using 2"x8" for the end beams?

The 2x8 will work fine, I like the look of more substantial. And in a few years will it have a roof and a snow load.

 

[slownsteady]

Part of the charm of a pergola is the shadows it casts - and the shade it can create. The bigger boards create bigger shadows (more shade when needed).
Previous discussions here have pointed out that a freestanding pergola may have advantages over one that is attached to the house. (debate will no doubt start again )
Both redwood & cedar come up on the Home Depot site, available for special order. I imagine Lowes has the same capability.

 

[bud16415]

I built something I roughly called a pergola over my hot tub last fall. but the intent was to put a tin roof on it from the onset. I’m no SW designer by any means but was hoping for that look and needing a cover of some kind for the 100” of snow that was coming. Sizing the lumber for casting a shadow and carrying a snow load are two different things. If it is never to be covered then wind is the only concern plus the little bit of weight of the beams.

 

[mbrittb00]

If your lumber is S4S and you're talking 24" OC, thats only 8 rafters,

The 8 rafters will be at 14" OC.

...crown the support...

I know what crowing is, but not sure I understand it in this context.

Thanks

 

[Snoonyb]

The 8 rafters will be at 14" OC.

Is that an aesthetic, or a mathematical spacing, because at 16"oc 2x6 span 16ft, and at that spacing you'll have 13.

I know what crowing is, but not sure I understand it in this context.

Just a reminder, crown up.

 

[mbrittb00]

Previous discussions here have pointed out that a freestanding pergola may have advantages over one that is attached to the house. (debate will no doubt start again )

While I'm not necessarily interested in starting a lengthy discussion, would you mind giving what are considered the main advantages of a freestanding as opposed to attached to the house.

Both redwood & cedar come up on the Home Depot site, available for special order. I imagine Lowes has the same capability.

I may be looking in the wrong place, but the only dimensions I can find for cedar are 1x sizes. I know I can just go in and talk to them, but I prefer to do as much research remotely as possible.

 

[Snoonyb]

Do you have their phone #?

Are you aware that when you place an order,"remotely", the vendor assembles the load and ships it, and you get what they load.

If you don't like the appearance of some of what you ordered, "remotely", guess who gets to return it, and wait for a replacement to arrive, [CLUE] It ain't HD or L.

While instead, were you to purchase at a lumber yard you can select the lumber, have the load built and delivered.

 

[bud16415]

While I'm not necessarily interested in starting a lengthy discussion, would you mind giving what are considered the main advantages of a freestanding as opposed to attached to the house.

I don’t know what SnS is thinking but I would say the biggest advantage to freestanding is you don’t have to violate the seal of the house siding system.

 

[mbrittb00]

I don’t know what SnS is thinking but I would say the biggest advantage to freestanding is you don’t have to violate the seal of the house siding system.

I would likely be attaching the ledger into brick.

 

[mbrittb00]

Is that an aesthetic, or a mathematical spacing, because at 16"oc 2x6 span 16ft, and at that spacing you'll have 13.

OC in an abbreviation for "On Center" correct.
Also, the rafters would be running in the 15' direction with their spacing in the 10' direction.

Just a reminder, crown up.

Still confused on this. How do you crown up a 2"x8"? What specifically are you talking about crowing up?

 

[bud16415]

OC is on center CL is centerline

When you sight down any long dimensional lumber on the width the piece may have a slight bend. You want the bend or crown up kind of like you would have camber in a beam and let gravity pull against the arch. I always lay all the material out flat and sort them according to crown and put the straightest two on the outside ends and gradually space them so the ones with the greatest crown is in the center. If it gets decked it is strongest this way and if it is something like you are building it will look straighter.

The counterpart to crown is cup and cupping and that is when doing plank flooring like in a deck. You want to then look at the end grain and put the cup up so the screws will pull it flat and it will then stay flat. Most people select the best looking side to go up and then have half the planks cup.

 

[bud16415]

I would likely be attaching the ledger into brick.

I don’t have a lot of experience hanging a ledger off brick work. old brick work is structural and with proper anchors I would think could support a great deal of weight. New brick work is mostly for looks and the wood structure is behind it holding the house up. I’m sure you can attach your ledger to it and be ok, but if it was to be load bearing I think you would have to study it carefully.