Building an arbour

Summary: Learn how to build an arbour, make the frame, anchor the frame, clad the frame and fit the roof.

Constructing an arbour in your garden can provide both a shaded area to sit and relax, as well as a decorative garden feature. It is important, however, that the garden is big enough to accommodate a structure of this type, as an arbour can take up quite a lot of space and be too dominant a feature in smaller gardens.

Arbours can be concreted in position or, if constructed on a concrete or paved area, secured with post bases, which can be bolted down onto the hard surface.

Materials

Arbour kits are available to buy from most garden centres. To construct your own arbour with the dimensions 2.4m (8ft) high, 1.5m (5ft) wide and 600mm (2ft) deep, you will need treated softwood timber in the following dimensions:

  • 4 corner posts A: 1.8m (6ft) x 75mm (3in) x 75mm (3in) L x W x D (If concreting the posts in the ground they will need to be 450mm (18in) longer).
  • 4 sheets of exterior plywood for the roof and fascia B: 1.5m (5ft) x 600mm (2ft) x 12mm (1/2 in).
  • 2 lengths of timber for roof battens C: 1.8m (6ft) x 50mm (2in) x 25mm (1in).
  • 15 tongue-and-groove cladding boards D: 1.8m (6ft) x 100mm (4in) x 19mm (3/4 in).
  • 3 cladding support bars E: 1.5m (5ft) x 75mm (3in) x 25mm (1in).
  • Timber for cross bars of the seat frame F: 1.8m (6ft) x 75mm (3in) x 38mm (1 ½ in).
  • 9 lengths of timber for seat frame and slats G: 1.5m (5ft) x 75mm (3in) x 25mm (1in).
  • 2 trellis panels H: 1800mm (6ft) high x 600mm (2ft) wide

The different components have been given a letter to help you follow the instructions.

Making the frame

The first part of the arbour to build is the seat frame.

  • Cut the length of timber F into three equal parts 600mm (2ft) long.
  • Construct the seat frame by screwing 2 of the of the timber lengths G to the ends of the 3 cross bars.
  • The next step is to attach the seat frame to the 4 main uprights A. The seat frame should be fixed onto the inside of the posts about 450mm (18in) above ground level. It is a good idea to get a helper to assist you with this task.
  • Use a try square to make sure that the frame is completely square to the posts. Then nail off-cuts to link the top of the posts to keep the frame square as you continue the work.
  • Screw the 3 cladding support bars E to the rear of the back posts. The first should be fixed at the top, the second 300mm (12in) above ground level and the third in between.

Anchoring the frame

With the basic structure of the arbour now complete it needs to be anchored in position.

Fixing to concrete:

  • Manoeuvre the structure into position and mark with pegs where the holes need to be dug.
  • Remove the pegs one at a time and dig the holes, which should be about 450mm (1 ½ ft) deep and 300mm (1ft) square.
  • Fill the bottom of each hole with a layer of gravel about 100mm (4in) deep to prevent the bottom of the posts rotting and improve the drainage.
  • With a helper position the posts of the structure into the holes and use a spirit level to check that it is standing vertical and level. To make adjustments lift the structure out of the holes and add to or remove some of the gravel.
  • Mix the concrete: 1 part cement: 2 parts sand: 3 parts aggregate. The mix should be fairly dry, as it will support the post better than a wet mix.
  • Shovel the concrete into the holes. Frequently check the structure is still vertical and level with a spirit level. Use a wooden stake to compact the concrete around the base of the posts and remove any air bubbles.
  • Leave the structure for 2 or 3 days to allow the concrete to set hard.

Using bolt-down post bases:

  • Put the foot of each corner post into the metal sleeves of the post bases.
  • With the structure in place on the concrete or paved surface, mark the positions of the fixing holes and remove the structure.
  • Drill and plug the holes. Then screw the metal post bases in position.
  • Lift the frame into the sleeves of the post bases and check that it is vertical and level.
  • Tighten the bolts on the sides of each of the post bases to secure the posts.
After sliding the grooved edge over the tongue of the first board. Gently knock it down protecting the end of the board with an off cut.

Cladding the frame

  • Use panel pins to fix the cladding to the support bars. Fix the first plank to the support rails through its face. Use a nail punch to punch the head of the panel pin beneath the surface of the timber.
  • The grooved edge of the next board should slide over the tongue of the first board. Gently knock it down from the top protecting the end of the board with an off cut.
  • Pin the second board through its tongue so the fixings will be concealed punching the heads beneath the surface. Fix the rest of tongue and groove cladding across the back of the frame in this fashion.
  • Fix the remaining 7 seat slats G. Fix the front and rear slats first, tight against the corner posts. Fix the remaining slats in position using an off-cut as a spacer to set them evenly apart. Use two countersunk screws to fix each of the slats to the seat rails.
  • To finish off the arbour frame, lattice trellis H can be fixed to the sides of the frame. This will enable the plants to grow up the side of the arbour. The trellis panels should be fitted at the top of the frame, so there is a gap between the bottom edge of the trellis and the ground.
Protect the plywood by covering the roof with roofing felt. Cut a piece of roofing felt to cover the whole roof and nail it onto the roof with clout nails.

The roof

With the arbour structure now firmly fixed in position it is time to fit the roof.

  • Use two of the exterior plywood sheets B to make 2 gable ends. Sand the sawn edges smooth.
  • Draw a curve 1200mm (4ft) wide and 280mm (11in) high on the front gable. Measure from the mid-point of the gable’s base 280mm (11in) up towards the gable’s apex. Mark this point X. (see diagram below)
  • From point X mark two points 600 mm (2ft) either side of the mid-point on the base. Mark these Y and Z.
  • Knock a small nail into the gable at points Y, Z and X. Tie one end of a length of string to the nail at Y. Run the string up the nail at X and back down to Z. The string forming a triangle with the base must be taut.
  • Remove the nail at X and position a pencil in its place with the point at X keeping the string taut.
  • With the string taut describe an arc in both directions on to the gable to create the outline of the curve.
  • Remove the two remaining nails and use a jigsaw to cut out the curve.
  • Cut the lengths of timber C each into 2 equal lengths to make 4 roof battens. Fix the roof battens to the top edges of the inner side of each gable using wood glue and screws. Drive the screws through the outside face of the gable into the roof battens.
  • Fix the remaining two plywood exterior sheets B to the top edges of the gables. This will complete the roof structure.
  • Position the roof squarely on top of the posts and fix it in place with screws driven vertically down through the roof into each post.
  • Covering the roof with roofing felt will help to protect the plywood from the weather. Cut a piece of roofing felt to cover the whole roof and nail it onto the roof with clout nails.
  • The heads of the clout nails on the gable can be concealed with bargeboards. This can enhance the overall appearance of the arbour.
  • Stain the arbour with a preservative wood stain.

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