Arbor / pergola advice please

[bkmfred]

Hi
Please can you give your expert advice on timber choice for a garden arbor.
Will be 3m wide 0.6 deep.
Would like a chunky type arbor.
For the 4 posts was going to use 4" x 4" planed and treated fence post 10ft length. But they look bit too thin. Can get 5 x 5 but they're unplaned and was planning on painting the posts white and might look fairly rough.
Found a supplier who has 5 x 4 planed playground posts in 10ft so thinking about these.
For the 3m crossbeams should I get treated timber?, thinking 2" x 8". But I cannot get these planed and again may look bit rough.
Was planning on painting/staining these beams brown and also the boards to go on top of these. Would it be pointless getting untreated timber and putting some preservative on it and staining? Want this arbor to last a long time. Don't want to spend a fortune, 5 x 4 posts will cost approx £60 and happy enough with that and whatever the cost for the rest
Also any advice on best exterior wood paint for posts and stain for beams etc. Thanks for any help

 

[MMUK]

If you think 4" x 4" is not enough, bond together four 3" x 3" posts to make a 6" x 6" post. Costly maybe but you could stand an elephant on it.

Another alternative is to use 4" x 4" tanalised sawn and then clad it with 4" x 1" PAR on two sides and 6" x 1" on the other two sides to end up with something around 5 1/2" square.

 

[Chrispy]

Depends on what kind of paint you end up using too, I think the water based garden/shed paints actually work and look better on sawn timber as you get a better colour density.

 

[John15]

Welcome.
I would use all treated timber. It looks good and is long lasting - apply preservative to the cut surfaces. I think 4" x 4" is fine for the uprights. I'm not sure if treated planed timber is available in Derry, it is on the mainland and it's easier than paint to recoat after a few years. For the top cross timbers 4" x 2" or 6" x 2" will be fine, again treated. The bracing timbers can be 2" x 2".
I hope this helps.
Cheers,
John

 

[bkmfred]

Apparently the treated 5x4 playground posts will not split or crack. And the other posts will eventually?
Thanks for other ideas, tempted by the 5x4. Thought 2" x 8" crossbeams might beef it up a bit, sounds like treated is the best option then.cheers

 

[bkmfred]

Back again.
Project ongoing
Went with 5x4 playgrade posts x 4, painted with sadolin superdec white satin
2 main crossbeams 3m, 8x2
7 upper beams 1.1m 6x2
3 2x2 slats at top (All above beams Sadolin Exterior Translucent Woodstain dark oak)

but stuck on final assembly
7 upper beams will be notched maybe 2" and slot down on main beams.
What is the best option to secure these.
1. Screw straight down with big deck screws? Whats best to fill hole then to stop water entry? and allow removal way in future if needed for restaining.
2. Toescrew in from underneath, dont like this as never done it and will be visible and prob make a mess
3.Buy Kreg HD Pocket hole jig and 2-1/2 exterior screws, but this'll cost £40, already gone overbudget,
4. Small angle brackets, would small be OK, thinking 30mmx30mm x 20wide. Any bigger would be visible

Any advice appreciated, keen to get this finished, posts planted last week and ready to attach beams now.
(tried to upload pic of posts, but no joy)
note there is only 0.6m total width between posts. Worried about stability when the wind picks up. Would 4 angle brackets and the above notched beams with top slats keep this thing secure? Posts concreted in 2ft on gravel bed.
Trellis to get added inside posts, stained dark oak . White picket fence at both sides to follow at some stage.
rgds

 

[John15]

Hi,

I would screw your short notched upper members to your main cross-beams with some fairly hefty screws. After drilling your pilot holes and countersinking, brush in plenty of preservative to protect the timber around the screws.

You have chosen very hefty posts and beams but if you are still concerned about twisting in high winds then fix diagonal bracing between the posts and I would say definitely fix bracings between the posts and the beams.

Galvanized angle brackets should be OK for fixing the beams to the posts.

Hope this helps.

John

 

[bkmfred]

thanks John, I have SS carraige bolts for beam to posts, 2 per post. and there is a 2" check taken of the top of the post for the main beam to rest also.
OK, so to screw down I'd
Countersink ~ 3"
pilot hole thru both timbers
5" screw ? are deck screws too light duty?

 

[bkmfred]

excuse my stupidity
Do you mean the screw on upper beams will just be countersunk and flush and need to be at least 6"?
or
do I drill (wider than screw width) maybe 3" into upper beam, then pilot hole, then insert screw, (this was why I mentioned filling the hole to prevent water)
I'm not often around wood u can tell!

 

[John15]

I am assuming you will be cutting a 3" notch from the top members to locate over the cross beams. You will then screw through the 3" notched timber into the cross beam using at least 6" screws or preferably a slightly longer coach screws. You will need to predrill for these fixings, a hole size about half the diameter of the screw. The countersinking operation is only to accommodate the head of the screw or if using coach screws and washers then no countersinking in necessary.
I hope that makes sense?
John

 

[bkmfred]

crystal clear, thanks again

will try post a completed pic.

 

[bkmfred]

Sorry 1 final question

In your opinion would u choose
Timber fix screw or
M8 SSteel coach screw (3 times the price!)
thanks