They comprise usually of 4 inch sq. treated posts concreted into the ground or with metal inserts concreted in at 5 to 6 ft intervals.
The minimum height clearance under the top rails should be 7 ft – so trailing/hanging foliage clears head height.
Fixed to the post tops along the length/around the post construction should be the bearer rails 6 inches by 2 inches or 4 inches by 2 inches, these can be toothed-in to the post tops by cutting a rebate into the post top and fixing through with screws or nails.
It is important to have the post tops level with each other if it is an arbor or pergola, but if the plan is to follow a sloping path up or down a gradient (a rose walk) – then the post tops should reflect the path slope.
When all the post are in place, are upright and the concrete has made them firm – check that the tops are level/uniform height.
Fix the bearer rails in place along the post tops (as already stated).
Using 4 Inches .by 2 inches treated rails – cut the cross rails that fix across the bearers rails at right angles.
Cut these with an overhang of 4 to 6 inches each side – a chamfered end is preferred by some – scalloped or just a square end.
These should have a toothed joint taken from the underneath to fix onto the bearer rails, no more than 1.5 inches. on a 4 in rail, (third of thickness) and fixed down from the top with a screw or nail.
Put these top rails every 18 inches to 2 ft.
If making a pergola against the building then a bearer rail will need to be fixed onto the wall with the correct bolts.
Make sure all timber is of a good quality and of pressure treated type and if concreting the posts straight into the ground then make sure that you give an extra coat of preservative for good measure!
These are perfect for climbing roses, wisteria, clematis, grapevines!
You should now have a good idea on installing Arbors, Pergolas and Rose Walks in the style of an English Country Garden!
(c) Copyright 2013, Mark Cook, All Rights Reserved. Written For: gardenconstruction.net