pergola - design and sizes questions

[miles_hot]

I have an unevenly curved path over which I want to construct a pergola.

At the moment I have in mind 3x3" uprights and 1x3" (arranged vertically) cross beams across the path and 1x3" (again vertically) members between the posts following the rough curve of the path (I'll call these length beams to differenciate these from teh cross members.

In a normal rectangular pergola the lenght means sit on top of the post (possibly with a 25% housing joint and the cross members sit on top of the length beams again with a housing joint. All beans stick out a little way with some decorative curve on the end.

My problem is that there will be few, if any right angles in the plan view of this pergola. Thus I can't easily follow the norm as each length member joining the posts will have to be jointed to the next and it will all look very messy.

With this in mind I am tending towards jointing the cross and length beams in the same plane - using halving joints and having this joint fully set into the top of the post. Thus the top of the cross beam, length beam and post will be level. I am also going to have some diagonal bracing on each of the angles. The beams will intercept the post along the centre line and thus there will be c. 0.5 - 1" of wood in the corners at the top of the post once the jointing is sorted out.

The questions are;
1) is this a sensible idea (I know it's a lot more work than the normal but it just feels that the normal will not look good).
2) are the dimensions OK?
3) Do I need to allow an overhand on the cross beams or given the more "oak frame" look and the design do you think that overhanging bits would look silly
4) i am thinking of running stainless steel wires between the cross and length beams to provide something for plants to follow - will 1" members be too thin to take the strain without bending to a silly degree

Many thanks, sorry for the huge post and I look forard to your answers / comments

Miles
PS the wood will either be pressure treated fending stuff or oak.

 

[EddieJ]

I guess that timber sizes will come down to personal preference, but I wouldn't consider post sizes of less than 100mm x 100mm and horizontal sections of 100mm x 47mm. Anything smaller could just look mean and weedy. Bigger is better!
I'm not very good at explaining how to set out, but if you imagine that you are removing the sections of say a tangerine and placing each segment tip against curve. Using this technique, you can quite easily make free flowing curves that intersect each broad section from the tip of the preceding one. (I'll try and draw it and paste it up on here)
In respect of oak or softwood, I work with green oak for a living, but wouldn't necessarily recommend it. It all depends on the age and style of your property and setting. If it was me, I would probably just use pressure treated softwood, as by te time it is planted up and weathered in, the expense of using oak would be wasted.

 

[miles_hot]

The house is a few hundred years old but has little or no period features (other than small windows). We both love Oak frames and would certainly build using that technique if we were ever mad enough to build a house.

Other other thought that was occurring to me was to use the same size timber or possible 1 inch smaller for the cross and length beams as for the posts.

I'm interested in your views on oak - what would put you off? Is it "just" the cost or are there other considerations?

I have to admit the fruit bit has me foxed

Miles

 

[big soft moose]

I'm watching this with interest as swimbo wants a pergola built against the house to shade part of the patio (further complicated by the fact that we're renting so it has to be dismantalable when we leave).

i'm looking at using oak framing too (at least for the main beams) not least because we oder huge loads of oak at work (from vasterns or venables normally) and I can tack my requirements on and thus get it cheaper.

 

[OPJ]

I'd go with EddieJ's advice, unless perhaps this is a fairly small or narrow structure, in which case, using 3"x3" posts may work? I'd still thicken the rails a bit though; 1½" would look good.

 

[miles_hot]

I'd go with EddieJ's advice, unless perhaps this is a fairly small or narrow structure, in which case, using 3"x3" posts may work? I'd still thicken the rails a bit though; 1½" would look good.

The path is about 1m wide so the structure will be at home 1.5 - 2m wide. I think I'll take the advice about thickening the rails - the only question is do I stop at 1.5" or should they be the same size as the posts...?

Miles

 

[gatesmr2]

Hi Miles

I am also intending (well swmbo came up with the idea :shock: ) to build one but i (she) wants an octagonal design.
Spoke to a friend who does a lot of landscaping for a living as i had thought about 3 x 3 and 2 x 4 for the top, the top is fine but he told me they never use anything less than 4 x 4 for the posts.

I am still in the design stage but he also gave me another tip that i doubt will be of much use to you as your going to a curvy style, set the uprights out then build the top on the ground and then lift it onto the posts. Saves a lot of working above your head.

Hope this helps and will be watching with interest how you do this.

Martin

 

[big soft moose]

Saves a lot of working above your head....

.... but means lifting an incredibly heavy piece , potentially on your own. each to his own but i would prefer working above head height (or maybe just using step ladder) to trying to lift a top section made out of 2x4 and 3x3 once its assembled.

 

[gatesmr2]

Big Soft Moose

I simply meant that with an octagonal design etc it would be easier to build on the floor and then get a few friends to lift it into place.
I can see doing it on your own would be very hard if not down right dangerous :shock:
Only going by what a friend who does this for a living has told me is the easiest way. He has other people who help him so again not doing it on his own.
I think setting in eight posts all at the right angle, height and make sure they are straight is going to be the tough bit but who am i to question my wonderful Mrs :?

Martin

 

[miles_hot]

I am going to use the metal post type fitting - initially I was going to build a little pad and use the bolt down type but the pads would have to be too big. Now I am going to use the spike type however I will be using the sort the tighten with a pair of bolts so that the post can be lifted in and out. I intend to set all the spikes in the ground, set all the posts in vertically (maybe with some arrangement to hold them so - outriggers etc...?). Offer everything up and mark out all the joints and then take it all down again (possibly in stages) to make all the joints. Put it back up with joints going in in situ unless components (like the arch sections) present themselves as easy to move and sensible to do bits.

Interesting to hear another vote for the 4x4 post...I have tended to 3x3 to reduce the visual weight, they're what are used for fence posts with a much bigger sail area, easier to handle and rather cheeper... Rats.

Miles