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Making a tree house

Every tree is unique, so the shape and dimensions of what you build will be quite different to ours, but the general process will be the same. Before you start, have an arborist or tree surgeon check the tree for safety. Be wary of rotten wood and the potential of falling limbs.

1. Kids can reach the tree by walking up the ramp or by climbing the rope ladder.

2. There’s plenty of room for everyone when the gang gathers for a bit of fun in your backyard.

3. The ramp provides easy access to the broad low fork, which is the main feature of the tree.

Tree house
GATHER YOUR SUPPLIES
Timber for entrance deck

  • Back/front (2) 190 x 45 x 800mm LOSP pine

  • Joists (3) 190 x 45 x 710mm LOSP pine

  • Long posts (2) 90 x 90 x 1200mm LOSP pine

  • Short posts (2) 90 x 90 x 600mm LOSP pine

  • Decking (11) 70 x 19 x 820mm merbau decking

Timber for ramp

  • Ramp (2) 190 x 45 x 2200mm LOSP pine

  • Battens (2) 70 x 19 x 360mm merbau decking

  • Rungs (12) 70 x 19 x 450mm merbau decking

Timber for platform

  • Posts (4) 90 x 90 x 1600-2700mm LOSP pine

  • Bearers (2) 90 x 45 x 1600-1900mm LOSP pine

  • Joists (4-5) 90 x 45 x 550-950mm LOSP pine

  • Diagonal braces (2) 90 x 45 x 1660-2230mm LOSP pine

  • Flooring 2400 x 1200 x 15mm exterior ply

  • Cross rails (3) 90 x 45 x 1200mm LOSP pine

  • Side slats 70 x 19mm x 25m merbau decking

  • Ladder rungs (3) 70 x 19 x 450mm merbau decking

YOU’LL ALSO NEED

  • 75mm batten screws; 690mm ground screws (7); luggage straps (2); 12mm rope (20-30m); plastic garden edging (50m roll); weed-mat; hardwood pegs for edging and rope ladder; playground mulch; hired turf cutter (optional)

Notes:

  • Before starting, check whether you need council approval to build a tree house.

  • Adapt timber sizes to suit tree.

  • As it’s a play area for kids, avoid using CCA treated timber.

HERE’S HOW
To make deck
STEP 1 Cut the deck frame to size. Predrill the ends of the back and front, then screw to the joists of the deck using galvanised batten screws. Add the central joist.

STEP 2 Cut long and short posts to length, predrill and screw them into each corner of the deck frame so tall posts face the tree and central joist runs out from the tree. Use batten screws in both directions.

STEP 3 Cut decking to length, but do not fix in place. Screw four 90mm-long offcuts of decking to posts, parallel to central joist and flush with the top of the back and front.

STEP 4 Measure out for the ground screws. These are ideal for working around tree roots. If you hit a root, just relocate the screw. There are 2 on the back of the frame and 1 at the front, on the central joist. As the deck is to be located about 1600mm from the base of the tree, position the
2 back screws 1645mm from the tree, with their centres 400mm apart. The front screw is centred between the back 2 and a further 665mm away from the tree. Use a timber offcut for leverage to wind screws in well, making sure they finish at the same level.

STEP 5 Lift the deck frame onto the ground screws and use offcuts of the 90 x 45mm timber to pack out the gaps between framing timbers and the 90mm shoe openings
of the screws. Screw on from both sides.

STEP 6 Screw the decking to the landing, leaving equal overhangs at each side and 3-6mm gaps between boards. Cut around posts and use the decking offcuts you screwed on in Step 3 to support decking where it butts up against the post.

To make ramp
STEP 7 Screw 2 planks for ramp side by side with a pair of battens on the underside. The ramp should lead to a large fork in the tree. Hold in place between tree and deck to check length and mark in the tree shape at top. Try to keep the ramp slope under 25º.

STEP 8 Use a power saw set to cut at an angle, then chisel ends of the boards to fit the profile of the tree trunk. This will involve trial and error until the fit is acceptable.

STEP 9 Use a power planer to bevel bottom edge of planks so they sit flat on the deck. Once the fit is right, make sure the ramp sits tightly against the tree, then screw the ramp to the surface of the deck.

STEP 10 Cut rungs for the ramp – they are slightly wider than ramp. Screw bottom rung 50mm from base of ramp, with equal overhangs at each side. Add remaining rungs using 105mm spacer blocks made from decking offcuts for consistent spacing.

STEP 11 To avoid ring-barking tree branches, tie a pair of luggage straps around suitable tree branches above the ramp. Facing the ramp, drill a 16mm hole in each post, 100mm down from the middle of the top. Feed rope through holes from front posts to straps and knot off securely at each end.

STEP 12 Tie more rope to handrail and pass back and forth under ramp to each side to provide webbing between ramp and handrail.

To prepare ground
STEP 13 If there is a drop of more than 500mm, you should provide playground mulch to ensure a soft landing, extending it well beyond the climbing area and under the ramp. Mark out the area and remove the grass. A turf cutter is ideal for this task and can be hired by the half-day.

STEP 14 Unroll the plastic garden edging using the cut-grass edge as a guide. Drive in hardwood pegs at 800mm intervals and when below the level of the edging, screw the edging to the pegs.

To make platform
STEP 15 Mark out positions for platform posts. The platform fans out from the tree trunk following the main branches above. The platform’s long sides are 1600mm and 1900mm, with widths of about 650mm at the tree and 1100mm away from tree. Drive in ground screws at the 2 outer points and
2 inner points (avoiding tree roots). Cut posts to length (ours vary between 1600 and 2700mm in length) with inner posts angle-cut to fit under branches. Stand them in stirrups. Clamp and drive 1 screw into base of each post, to hold.
STEP 16 Use spare decking to prop outer posts so they’re plumb (vertical); drive pegs into ground away from posts in 2 directions, then clamp props to pegs and posts.

STEP 17 Measure about 780mm above the expected level of mulch on 1 outer post, and transfer this level to the other outer post. Clamp a side bearer to a pair of inner and outer posts. Adjust inner post until bearer is level and both posts are plumb, then predrill and screw in place using batten screws. Repeat for other pair of posts.

STEP 18 Starting with outer joist, hold it in place under bearers and inside posts. Check posts are vertical. As nothing is square, mark in angles at each end of joist and cut to suit. Screw between bearers using 2 batten screws at each joint and with top surfaces flush. Repeat for joist at tree, leaving a little clearance to the tree. Once 2 end joists are in place, measure between them to fit more joists spaced no more than 500mm apart, then cut and screw in place.

STEP 19 Carefully measure platform sides, including around tree, and cut to size plywood for flooring using a power saw, and a jigsaw for the curves. Cut outside the lines at first as you can always trim off more later, if needed. When it is a good fit, screw down to the bearers and joists.

STEP 20 To provide an upper frame for the side slats, install 2 diagonal braces that either follow the slope of a tree branch or run out from a branch. Screw to pairs of inner and outer posts, down to the floor where possible. Also install 2 cross-rails over end joist, spaced 1000mm and 1400mm above the top of the platform, as well as 1 just short of the top.

STEP 21 Sand and smooth all edges, then give frame 2 coats of paint, here Dulux Weathershield Low Sheen in Boyzone. Also paint ramp and posts of deck, but not the merbau decking and rungs, or the rope.

STEP 22 Cut to fit slats that surround the platform, starting on the front side. Each slat will be of a different length, depending on tree branches and the slope of the brace. The bottom of the slats begin at the base of the platform frame, and the top of the slats extend about 100mm higher than braces. In the large opening, screw 1 slat next to each post and 1 in the middle so kids can still jump off the platform. Enclose small triangle, leaving a gap about 20mm between slats. Gaps between the slats need to be wide or narrow enough so kids won’t get stuck.

STEP 23 Screw slats to enclose the back side, also leaving an opening. Finally, cover the ladder end by screwing on slats from floor level to top of the first cross-rail leaving a ‘chute’ about 350mm wide for the rope ladder. Then attach slats from bottom of second cross-rail to about 100mm above the top cross-rail, leaving a window in the centre.

STEP 24 Check and rake area inside garden edging for unwanted rubble, then roll out and fit weed-matting. Trim as necessary and hold in place with weed-mat pins.

STEP 25 To make the rope ladder, bore 16mm holes 50mm in from the middle of each end of the rungs. Feed through two 2m lengths of rope. Leaving an 800mm tail, loosely tie a knot in each rope above and below the top rung, as close to the rung as you can. Tie a second knot 250mm further down the rope and feed on second rung. Tie a knot underneath and repeat for bottom rung. Check the rungs are evenly spaced, adjust if necessary, then pull all knots tight.

STEP 26 Drill a 16mm hole 25-30mm above floor level through the 2 slats beside the opening at back of the platform. Drill another pair of holes through the floor about 60mm back from the edge behind the slats.

STEP 27 Feed rope through slats and tie knots 250mm above the rung. Pull back and check on the length so all rungs are level.

STEP 28 Feed ropes through holes in floor, pull tight, then tie knots 250mm down from floor level. Pull rope ladder back and check all knots are bearing on slats or floor. Double knotting makes the ladder extra safe.

STEP 29 Drive 2 pegs through weed-mat into ground about 250mm out from platform, in line with ladder. Drive at a slight backward angle until a short stub remains. Drill a hole through pegs with a 16mm bit, feed through rope and tie a knot so rope ladder is taut.

STEP 30 You’ll need enough playground mulch to fill to a depth of 250mm. This will mean a truck delivery rather than bags. Barrow mulch into place and rake till even.