Pergola beam span

tc20

Hi folks,

I'm looking for a bit of help from the knowledgeable folk here - myself & FIL have been planning a pergola for his garden.
It will be built over an existing patio area, free standing. He would prefer minimal uprights, (4no) for a cleaner look.
We're looking at a 14' x 10' area, using 6" uprights. Simple design, with 1' overhangs beyond the uprights, so max length of beams is 16'.
My concern is around the length of the support beams, (they will be braced using 6x6")
Is 14' too much of a span between 2 uprights?
I would be planning on using 2x8" beams on the shorter side, and topping these with 2x10" on the longer span.
Top slats would be (notched) 2x4" (or possibly 2x6")


He's not keen on a 6 post design - from an aesthetic point of view.
Plan B would be to use 8 uprights, but with a wider middle opening of say 8'.
Can't post pics at the moment of what we have in mind but will do tomorrow.

cheers

Lumen

IMO 2x10" will be absolutely fine over 14ft.

A pergola only has to hold itself up.

tc20

Would it be more correct, from a structural point of view, to use the bigger (2x10") on the longer span rather than on the shorter side?

Lumen

I would just copy an existing design, like this.

It's less efficient than what you're proposing but more attractive.

listermint

Lumen wrote: »

IMO 2x10" will be absolutely fine over 14ft.

A pergola only has to hold itself up.

Not true. It has to hold up the weight of expectations of what it will turn out like when finished

tc20

@ Lumen - the photo you posted is pretty close to what we have in mind (simple pergola designs don't differ all that much imo)
The only real difference is that I had planned on double support beams (ie 2 per upright) on the long span.
My main concern is the possibility of beam sag across a 14' span.

Lumen

A pergola is similar in structure to a suspended timber floor, so just consult the standard joist span tables if in doubt. And that would be way over engineered for a pergola, since there's no finished floor, furniture or people dancing around on top. Unless your parties are way more fun than mine.

gctest50

Lumen wrote: »

IMO 2x10" will be absolutely fine over 14ft.

A pergola only has to hold itself up.

Snow load

...Ghost...

gctest50 wrote: »

Snow load

Minimal unless you close off the roof. The snow cant build up on a few narrow beams in the way it would on a closed roof.

mloc123

gctest50 wrote: »

Snow load

People always mentions snow load here.... as if we live in Illinois.

In the past 20 years we had one major snow event.

3DataModem

Sorry for hijacking the thread, but if you were looking for someone to do a similar job like this (in my case, the "pergola" will be connected to two walls over a patio) what sort of handyperson / carpenter / builder would you look for?

tc20

Thanks for the replies folks, much appreciated.

Location is 100m from the east coast, so I would wager that any snow load will be minimal, and as referred to above, its an open structure, so no roof.

I've drawn up a list of sawmills to contact with my shopping list, as based on availability, we plan to use cedar, larch or possibly douglas fir (FIL in easy on choice of wood)
A little knowledge is dangerous as they say, so I defer to the knowledegable posters here - the more I read up on timber, the more questions I have - timber grades for a start -
C16 seems to be the basic standard used here, are the woods I mention above likely to be a higher grade, or would C16 be suitable for me?
If i'm reading too much into this, stop me now

Lumen

gctest50 wrote: »

Snow load

On a pergola? What? It has an open roof.

Lumen

To demonstrate how incredibly badly you can build a pergola and still have it stay up, here's one I threw together in a few minutes whilst quite drunk one Sunday afternoon a couple of summers ago.

It was screwed together from bits of rotting scrap, and despite looking absolutely lethal, stayed up for a good couple of weeks before a mild storm wrecked it.

It was even strong enough to hold some painting sheets and thus become a gazebo.

WINNING

karlitob

tc20 wrote: »

Thanks for the replies folks, much appreciated.

Location is 100m from the east coast, so I would wager that any snow load will be minimal, and as referred to above, its an open structure, so no roof.

I've drawn up a list of sawmills to contact with my shopping list, as based on availability, we plan to use cedar, larch or possibly douglas fir (FIL in easy on choice of wood)
A little knowledge is dangerous as they say, so I defer to the knowledegable posters here - the more I read up on timber, the more questions I have - timber grades for a start -
C16 seems to be the basic standard used here, are the woods I mention above likely to be a higher grade, or would C16 be suitable for me?
If i'm reading too much into this, stop me now

If you could that list of sawmills that would be great. Thanks.

tc20

@ karlitob - here ya go -
I think I just searched for cedar suppliers Ireland and took these from what I found. Haven't contacted any yet.

Lumen

Wood Industries in Rathdrum are excellent and very responsive by email, in my experience.

I think Cedar is significantly more expensive and less durable than Siberian Larch, although looks prettier if you treat it regularly.

tc20

Lumen wrote: »

Wood Industries in Rathdrum are excellent and very responsive by email, in my experience.

thanks Lumen, i'll add them to my list - more local to me too.

gctest50

Lumen wrote: »

On a pergola? What? It has an open roof.

Until you winterise it

Lumen

gctest50 wrote: »

Until you winterise it

Then it ceases to become a pergola.