Small Timber Frame Porch

[Scott Holloway]

Hi All. I am going to build a little 9' x 18' shed roof porch and deck. I was going to build it out of pressure treated 6x6 posts but when I went and looked at my existing deck it seems all of those posts have twisted somewhat. I'm assuming that would completely ruin the look of some basic timber frame joints. Is there a way I could dry out these PT posts, if so would that stop them from twisting, or does anyone know of a sawmill near Alpharetta, GA (just north of Atlanta). I searched in Google and found nothing quickly. Thanx for any help.

[Stephen Edwards]

Are you planning on using the pressure treated 6x6 posts for the vertical uprights only? What are you planning on using to do the other framing, such as the floor system, and the roof?

[Scott Holloway]

I was going to use the 6x6's for the posts, bottom and top plates, and rafters. The longest span would be about 8'. 4x4's for purlins and knee braces. These would span about 6'. Trex decking and regular floor joists.

I just found a sawmill near here: http://www.timberridgefence.com/anderson.html
I think it is owned by the guy that put in my fence!

Do you think I can use the PT or should I get dried timbers.

[Gary Falls]

try to get your hands on some fir or hemlock. Pressure treated is so saturated with water and chemical that it twists, checks, and shrinks lots. I would only use the PT for the decking. Timber frame companys should be able to mill lumber to whatever size you want and even cut your joints if you want to take all the fun out of it.

[Stephen Edwards]

I was going to use the 6x6's for the posts, bottom and top plates, and rafters. The longest span would be about 8'. 4x4's for purlins and knee braces. These would span about 6'. Trex decking and regular floor joists.

I just found a sawmill near here: http://www.timberridgefence.com/anderson.html
I think it is owned by the guy that put in my fence!

Do you think I can use the PT or should I get dried timbers.

I have built many decks and porches using pressure treated lumber with very few problems. Of course, there will be the ocassional piece that warps or twists. You're gonna find that to be the case even with sawmill lumber, if not more so.

Personally, in my opinion, using the 6x6 posts for the floor band, roof support beam and rafters is overkill. That is, unless you specifically want the look of huge timbers. You can do this project much cheaper and plenty strong by using the 6x6 posts for the verticals and a double band of 2x8 around the perimeter with 2x8 joists on 16" centers. For the rafter support beam you could use a double beam of 2x6 with 2x6 rafters on 16" centers. I don't know what you plan on using for roofing material. If you're gonna use metal you could then put 1x4 PT stripping every 2 feet perpendicular to the rafters, to which you would screw the metal.

As Gary said, hemlock is an excellent lumber for outdoor projects, if it's available in your area. I don't think that there's much fir in north Georgia.

Good luck with your project and have fun!

[Scott Holloway]

Thanx Stephen. You're right, I'm going for the "look" of big timbers (although 5 1/2" isn't all that big. Turns out this sawmill is within 10 miles of here. So I'll certainly check their prices. Maybe a 7 x 7 post and then 6 x 6 cross members and 4 x 4 purlins. It will be a standing seam metal roof.

So you think the hemlock will twist more than PT? I'm just concerned that I would spend some decent time putting together some joinery only to see it twist and pull out. I looked at the 6 posts under my deck and by 9' tall they've all turned a little.

[Stephen Edwards]

Thanx Stephen. You're right, I'm going for the "look" of big timbers (although 5 1/2" isn't all that big. Turns out this sawmill is within 10 miles of here. So I'll certainly check their prices. Maybe a 7 x 7 post and then 6 x 6 cross members and 4 x 4 purlins. It will be a standing seam metal roof.

So you think the hemlock will twist more than PT? I'm just concerned that I would spend some decent time putting together some joinery only to see it twist and pull out. I looked at the 6 posts under my deck and by 9' tall they've all turned a little.

Hey Scott,

I haven't used any hemlock myself. However, I know of a 15 year old barn near here that's covered with hemlock and I've noticed very little warping on that. I don't know how it would hold up (warping) as a framing timber. All the oldtimers around here say that it's a stable wood. Another species that I know holds up well outdoors and inground is the heart of eastern red cedar, if that's available at the mill near you. In my experience it moves very little as it dries, unlike many other species.

Another consideration for your timber framing that I think looks nice, and still gives you the "look" that you want, is to possibly use timbers that aren't square in dimension. For example, for the rafters perhaps you could use full 3x6 or 4x6. That gives you the heavy feel of a timber framed structure and is usually more pleasing to the eye than using equal sided dimensions such as 4x4 or 6x6......except for the posts of course.

I'd suggest that you go see the guy at the mill near you and ask to see different sizes of timbers that he has in stock. Also, tell him what you want to do and ask for his opinion. If he's established for a long time and has a good reputation he's not apt to steer you in the wrong direction. Seeing the different sized timbers with your own eyes will take a lot of the guess work out of it, too!

One more thing......if you build this out of green lumber the kind of joints that you're talking about making are going to move as the wood dries and shrinks. Others may know of tricks that I'm not aware of to deal with this. Your best bet to avoid that problem, in my experience, is to use kiln dried timbers and pick good straight timbers to begin with.

Best Wishes,

[Scott Banbury]

Yer in Georgia--use Cypress.

Call some lumber yards and ask them who supplies them with dimensional cypress and then get that mill to cut your order to spec.

When you get to the building part, get in touch with me and I'll share my techniques.

[Scott Holloway]

I spoke with the local sawmill and he only has pine and agreed that cypress would be best. He recommended another lumber company and I called them and they don't have any large beams either. He mentioned he could order 8x8 cedar beams for about $16/ft. He then suggested I just use pressure treated posts. SO, since a 12' is only like $25 or so it looks like I am back to 6 x 6 posts from Lowes. Oh well, it was worth a few phone calls.

[Josiah Bartlett]

Another option is to use 4x4 for the posts and then wrap them with 1x stock to create larger posts. This creates better stability, since the box section you made should have the grains of each piece preventing the others from warping.

[Scott Banbury]

Scott, $16/ft is ridiculous. When I price my jobs I figure my cost for green cypress cut to size will be $1.25/bdft--$6/lineal ft for 8x8.

Keep looking, maybe closer to the coast.