Pergola From 4x2s and 4x4s

This pergola is made from easily obtainable construction wood and various fasteners and can be constructed using basic tools. The overall size of this particular one is 4.8m x 3.6m (ca. 15¼" x 12") coverage. Lengthen or shorten the 4x2s accordingly to fit your required size.

The pergola is constructed from 4x4 and 4x2 timber that translates to 10cm x 10cm and 10cm x 2.5cm respectively after shrinkage and conversion to sensible measuring units. In my neck of the woods (Cumbria, NW England), pressure-treated construction-grade pine is the best bang for your buck. For a size of 4.8m x 3.6m (ca. 15¼" x 12"), you will need:

1. 4 x 4x4s, 2.4m length
2. 4 x 4x2s, 4.8m length for the two sets of joists.
3. 13 x 4x2s, 3.6m length for the cross members that fit over the joists. This amounts to a spacing of ca. 41cm. Use more is you like a tighter spacing between the cross members.
4. 8 x 15cm coach bolts, nuts and washers or pieces of threaded rod
5. A box of 60mm screws
6. Outdoor/shed/fence paint
7. 4 off 4x4 metal postbases
8. A selection of offcuts for the braces, collars and finials

The minimum tools required are a jigsaw, a straight-cut saw, a drill with various drill bits, measuring tape and a spirit level. And a hammer, of course. A router is also useful to relieve some edges and put fluting on the posts. You will need a lathe for turning the finials, which are optional, but add a nice touch.

Cut the decorative ends of the cross members using a jigsaw. Use any design, but keep it consistent by using a template. I used a template from plywood since a cardboard one would get knackered over time.

In my design, I only recessed the inner 9 (if you like the spacing I used) cross members to fit over the 4.8m joists by a depth of the wood thickness, i.e. 2.5cm plus a few additional millimetres to compensate for the vagaries of rough-sawn lumber. I used lots of cuts with a circular saw and a chisel to make these recesses. The outer two sets of cross members were not recessed and end up standing proud over the inner cross members, which was a good look.

The last pic skips ahead and shows how the recesses of the cross members would fit over the 4.8m joists.

I used a 6mm radius router bit and cut 3 grooves on all 4 sides of each post, and relieved the edges with 45° chamfer using a router. This took some time and you should plan this work to minimize the number of router sled adjustments and cutting-tool changes that are required.

The collars on the posts are useful for supporting and aligning the joists and also serve as a stop guide for the router when cutting the flutes. For this, I used some 2x2 (45mm x 45mm) offcuts and also chamfered the edges that face towards the middle of the post. The top collar was attached at 250mm from the top, the lower collar was attached 600mm from the bottom.

I already had a solid base to stand the pergola on, so I did not need to dig post holes. I used steel postbases and placed these on concrete blocks. This allows me to move the whole structure while still developing the rest of the garden.

The last pic shows what the posts look like after they have been decorated with the flutes and chamfers, and then painted.

You can use diagonal braces, but I went and made fancy braces by glueing two spare 4x2 pieces together to make up a 8x2 piece of wood and then transferring my cardboard design onto it. Using the cardboard cutout approach, I was able to get a best-fit on the available wood surface for cutting the shape of the braces. I used a jigsaw for most of this work, and also relieved the exposed edges with a 45° chamfer using a router. Note that there are two brace designs, since one design supports the 4.8m joists and the other supports the higher-situated cross members.

These braces will eventually be attached to the joists and cross members with 10cm 4x2 blocks, so have some of these ready too, for the next step: painting!

If you plan to paint or otherwise treat your wood with a preservative, it is a good idea to paint each piece before putting the structure together. It will save you much time and ensure that every surface is adequately protected from the elements. You will also not have to fiddle about with your paintbrush in all the nooks and crannies.

I used a cheap gell-based fence paint (7.5 litres) and I had to put two coats of paint on most of the pieces. It only took a few minutes to paint each piece of wood.

You can either make or buy finials or simply choose to not have any. I wanted to "tart" my pergola up, so here is how I made them on a lathe: Start with a 4x4 offcut, centre it and mount it on a lathe. Use a roughing-out gouge to make a 10cm diameter shaft. Mark the cutting lines and shape the finial using your preferred gouge technique. Making a sphere that does not turn out egg-shaped is not easy! Leave a stubby bit that will fit into a recess on a mounting plate. I glued the finial to the mounting plate, and then later screwed the mounting plate assemblies into the top of each post.

Start the construction with the two sets of 4.8m joists on the floor and use clamps to hold them in place against the posts and collar supports. See how useful the collars around the posts are? Drill recesses for the bolt heads and nuts, then follow through with a long drill for the bolt shaft and run your coach bolt or threaded rod through to attach the joists to each post. Do this for each post. Once the two halves are complete, raise the two halves of the construction and get a few helpers to hold them propped up while you do the next step: Attach the two sets of non-recessed cross members using the same method. You will need a ladder or step here.

Measure the spacing between the cross members (ca. 41cm in my case) and fit them so that the recesses drop over the joists, and secure them with screws. Use outdoor-proof wood glue like Titebond III (that's a Roman 3!) or construction glue between the contact surfaces for extra strength.

Attach the braces and finals as a final flourish. You should now be the proud owner of a pergola!

I did the "Arts and Crafts" thing and plugged all the holes with raised wooden plugs which were then painted.

Now for the rest of my garden...