Build a Timber Frame Style Garden Pavilion Gazebo

Part 1 – Build the Timber Frame Style Pavilion

Timber Frame Design

Here’s the 3D model I created in Sketchup.

Timber Frame Pavilion on 10′ by 10′ centres

The peak height of the pavilion is 11’3″. The large sloping shed roof faces the south with another smaller roof on the front facing north with a clerestory type opening above. The structure is built from red cedar and fir, and topped with a metal roof.

Peak height of 11’3″

I’ll add a rain gutter off the back to collect water for the garden. The rafters and beam ends have a quarter ellipse profile in the same fashion as the woodshed I built earlier in the summer. The head clearance is 7 feet and in the future I’ll add a wooden deck or concrete patio.

Four 6×6 red cedar posts on galvanized saddles

The posts will sit on galvanized metal saddles attached to an anchor bolt embedded in a 9×9 inch concrete pier. The footings are dug down below the frost line and sit on a hard clay layer.

Side girts of 2×8 red cedar extend past front posts

Connecting the posts are 2×8 side girts. These extend past the front posts.

Top beams are 6×6 and front roof beams are 2×8

And will allow me to build a small front roof section angled opposite to the main roof.

Front roof section cantilevers off side girts

Topping the posts are two 6×6 beams. A pair of 2×8 beams will support the front roof section.

Main roof rafters are 2×8 fir

14 curved corner braces will give rigidity to the frame. 2×8 rafters span the top beams with blocking added between them for lateral strength.

Main rafters have 2×6 fir support blocks between each

Over the front beams sit 2×6 rafters topped with 1×6 strapping.

Main roof strapping is 1×8 cedar

On the back I have 1×8 strapping over the main roof rafters.

Tin roof sheets

I’ll trim out both roofs with cedar 1×4’s before installing tar paper and metal roofing.

Laying out and Making the Concrete Pier Forms

Batter boards made from stakes and level ledgers

I laid out the post locations using string and batter boards then dug the footing holes. The batter boards are made by hammering in three stakes and connecting them with level ledger boards.

Ledgers attached to stakes to create a level plane

Weights hang from these mason lines and cross over the center of each pier form.

Strings drawn across center of each form

These lines are strung over the ledger boards 10 feet apart and are square and level. The tops of the ledger boards are all on a level plane.

Strings are level and square on 10′ centers

The pier forms are simple boxes made from half inch plywood and 2×2’s. I added a fillet strip to the corners to form a chamfer.

Pier chamfer is created with wooden fillet strip inside concrete form

I can remove the lines once all the forms are leveled and squared to these strings, and secured to small stakes in the ground. All the tops of the pier forms are now on the same level plane.

Forms have vegetable oil smeared on to keep cement from sticking

To keep the cement from sticking to the plywood I apply a good amount of vegetable oil to all inside surfaces.

I pound in some rebar to reinforce the piers. Pounding the rebar into the hard clay at the bottom of the hole keeps it in place roughly in the center of the form.

Fill Forms with Concrete

Holes and forms filled with cement

I mix concrete and fill the holes and forms. This is my second wheelbarrow load for this form. I use a short length of rebar to work the concrete and settle it. I overfill the form then lightly tap it to bring bubbles to the surface. I’ll then let it sit and settle for a few minutes.

A chamfer on the top edge is formed by hand with small trowel

Then I scrape off the excess and form a chamfer on the top edges with a flat margin trowel. I’ll use a flat trowel and marks on the form to find center, then work in an anchor bolt before the cement sets up.

Anchor bolt embedded in wet cement in center of form

I cover the forms with plastic and leave to cure for a few days.

Stripping Pier Forms

Piers are revealed when forms are disassembled (or stripped) after a few days

It was very hot and dry when I poured them so I didn’t want the concrete to dry too quickly. The plastic helps to prevented that.

When set, I stripped the forms. For me, it’s like unwrapping a present. It’s always cool to see how it works out. I’ll remove the screws from the small stakes, then the screws holding the four sides together. Then gently pry off the plywood panels.

The pier forms needed to be a bit taller where the ground sloped slightly away. These forms required 2×2’s to hold them together.

I label the form sides in case I need to reassemble them later

As the forms came apart I labeled them with a sharpie in case I wanted to reassemble them for another project.

Exposed piers are kept covered with plastic to properly cure

I cover the piers with plastic for a few more days to keep from drying too fast.

I scrape off any sharp edges or corners with a piece of wood while the concrete is still soft.

I’ll leave the batter board stakes and ledger boards as is for now. I might need them later for temporary bracing supports.

Selecting and Moving Lumber to Garden Site

We have lumber milled from our own trees stickered and drying in the back of the property. Now that my drawings are done, I can select the lumber I need and move it to the garden with the truck.

In this first pile I have two long 6×6’s for the top beams. These 6×6’s have a bit of a bow to them but its not too bad. I’ll orient them so the curve of the bow becomes the crown.

Selecting beams and posts from a drying pile

In another drying pile I have a stack of two by eight fir for the rafters. It was disappointing to see that many of these boards twisted while drying. Some turned out to be unusable for rafters but most I was able to salvage.

In yet another pile I’ll try to find the straightest stock for the posts. It took a while to sort through and find the best candidates. I also found some very straight two by eights for the girts and front roof beams.

It’s great to have a few extra sawhorses on hand to organize all this lumber and to have it all at a convenient working height.

Prepping the Posts

Cutting timbers with a circular saw

Having everything I need, I’ll start with the four posts. The rear posts are cut to length by marking all four sides with a large speed square, then making four cuts with a circular saw, and finishing it off with a hand saw. I’ll get two rear posts from this long 6×6.

Cutting posts to length

I then cut the two taller front posts to length in the same fashion.

Post ends trimmed to fit galvanized metal saddle

The post saddles I’m using are adjustable in case the anchor bolts are out of square. These particular saddles are made for a five and a half inch post. I need to trim the ends of each post with circular saw and chisel to fit these saddles. I believe the manufacturer does makes a similar saddle that fits a full dimension six by six.

Rear posts have half lap cut in them

The tops of the back posts have a two inch deep by six inch long lap cut to receive the side girts. I cut these by setting the depth of my circular saw to two inches and make a series of thin slices into the post. I use the speed square as a guide. Then I break these thin segments with a hammer. Then use a wooden mallet and sharp chisel to clean up the cut.

Front posts have a deep slot cut on the outside face to receive the side girt

I chamfer the edges of the rear posts with a power plane.

Chamfer edges with a power plane

The front posts have two slots cut in them. One on the side face to receive the two by eight girt, and another on the front face to receive the front roof beam. I’ll lay out these cuts on the posts with pencil and square, then set the depth of my saw to two inches and cut a series of parallel slices.

Front post deep slot cut with circular saw blade 2″ deep

One next face of front post a 1″ deep slot is cut to accept the upper side front roof beam

Then I’ll rotate the post a turn, set the depth of my blade to one inch, and cut the other slot. These slots overlap slightly so I’ll need to make a small notch in a front roof beam later to compensate.

And I’ll chamfer the front posts with the power plane.

Stand up and Secure the Four Gazebo Posts

Standing up a front post and securing with temporary braces

I’ll set the post saddles on the piers and snug the nut finger tight. Starting with a rear post, I stand it up, set it in the saddle and position it. I’ll drill pilot holes in the bottom of the post and run in a screw on either side.

Final post being erected

I have temporary bracing ready, and attached with a screw into a small stake pounded into the ground. I use some clamps to hold the post while I plumb it with a long level.

I’ll do the same for the other rear post. It’s good to have everything ready and tools and screws within arms reach if doing this by yourself.

The taller and heavier front posts were a bit more of a challenge. I had a sawhorse ready to stand on to help with plumbing and braces.

Attach the Side Girts to the Posts

Installing first side girt

Next, I cut the side girts to length and mark their crown for their upside orientation, then chamfer these with the power plane. On one end I’ll cut out a two inch by six inch notch. This will allow the beam to fit neatly over the top of the rear posts. I attach these to the posts with some construction adhesive and lag bolts. The heads of the bolts are countersunk with a forstner bit, then predrilled with quarter inch bit.

I have a board clamped to the rear post to catch the girt as I’m positioning it. A clamp holds the rear end in place as I drill and run in the lag bolts with an impact driver.

Side girt on other side being attached with glue and screws

The other girt didn’t go as well due to a slight warp, so I removed the rear clamp to get it to fit. I used a few clamps to pull it into the groove on the front post before running in the lag bolts.

See Part 2