Below you will find a detailed guide on how to make a glass roof pergola on a budget. In total it adds up to around £300 for all the materials. Why transparent roof? Well, in Scotland sunlight is scarce and rain plentiful - hence a perfect solution if you like your BBQ.
I hope you will find it useful!
Step 1: What Will You Need?
- 6 Acrylic Sheets (4mm thick, 200cm long and 60cm wide) the link is for a different size, but just ask the seller for a quote on the size you require. He`s really good and the cheapest I could find online.
- 6 Timber Battens 3x2 (63mm x 38mm), these come cut to standard 2.4m length, hence need to be cut down to 2m
- Wood Glue make sure to get one suitable for outdoor use
- Table Saw - I use the Evolution FURY6 Multipurpose Table/Mitre Saw and I've got to say it has been brilliant. Also, extremely good value for money, especially considering you are actually getting 2 different tools for the price of one.
- Angle Grinder - perhaps the most versatile tool in any workshop, definitely worth getting a decent one straight away. I went through several cheap-ish ones before I got the Bosch blue series. Never look back, great machine.
- Clamps - Again, the tool you will be using for most of the project, avoid buying the plastic ones as they break easily.
Step 2: Sanding the Timber
To keep the budget low I used fence posts for the main structure. These are way cheaper than construction timber but they are rough sawn hence need sanding.
You could either use an orbital sander or if you want to save time, use the angle grinder with hook and loop backing pad. Please remember to use your health and safety gear when using the grinder!
Using the 60 grit sandpaper, sand all the post on all sides. This will not only improve the appearance but also it will reduce the amount of stain you have to apply later on.
Step 3: Staining the Timber
It is far easier to stain your timber before you put the construction together.
I used decking stain for this particular project but any weatherproof stain will do just fine.
When applying the stain, follow the wood grain. Apply minimum 2 coats.
Step 4: Cutting the Posts.
You will need 4 posts cut to around 211cm (these will make the foundation of the pergola) and 2 posts cut to 195cm (these will be the horizontal posts, at the top of the pergola, on both sides) - as the standard posts are 2.4m long you will have 2 pieces -around 45cm each- leftover, keep these on the side for now.
Using the tape measure, mark the desired length on the post. Take the set square and draw a straight line on all the sides of the post. These lines will work as a guide for your saw. Using the handsaw, cut the timber, making sure you follow the lines. You want to end up with a nice square cut. Repeat the process with all the 2.4m posts (4)
Top tip: clamp a spirit level to the post and use it as a fence for the hand saw.
Step 5: Cutting Out the Joints
For this step, you will need two 195cm posts and one 3m post.
Measure the exact width of your posts. In this case, they were 9.5cm wide. Now take one of the 195cm long posts and mark a line, exactly 9.5cm away from the end. Place your set square on the line and mark the middle of the post with a line. Using the handsaw make a cut following the lines. Make sure to make the cut on one end of the post only. Repeat the process for the second 195cm post.
Now take the 3m post and make the same joint cut on both sides.
Step 6: Making the Struts (diagonal Braces)
Take the two 45cm pieces left over from cutting the posts.
Measure 9.5cm (posts` width) from the end and mark it with the line creating a square. Now draw a line from the outside right corner to the bottom left corner of the square. This will mark a 45-degree cut guideline. Clamp the piece to the table and make the cut making sure you follow the line. Its crucial that the cut is exactly at 45-degrees. Repeat the process on both sides for both pieces.
Using the countersink drill bit, predrill two holes on each side, right in the middle of the 45-degree cut as shown in the picture.
Step 7: Putting Up the Front Frame
For this step, you will need 2 fence posts cut to 211cm, one 3m posts with joint cuts at both ends and 2 struts.
Predrill the ends of the 3m posts, right in the middle of the joint cut as shown in the picture. Now, apply a generous amount of wood glue to the end of the 211cm post. Place the 3m post at the top, making sure the connection is square and secure it with 15cm construction screw.
Next, take the strut and apply wood glue on both sides. Connect the 2 posts and secure the strut with 4 construction screws. Wipe off all the excess glue. Repeat the process on the other side.
Step 8: Securing Foundation Posts to the Wall.
For extra stability, you should attach the remaining two foundation posts to the wall.
Firstly place the remaining two 211cm posts, upright 3 meters apart from each other (outside end to outside end). Next, using a knife or a nail mark the position of the post on the wall. Predrill at least 3 holes in the wall, right between the lines (bottom, middle and top) and insert wall plugs. Take one of the construction screws and using the angle grinder cut the head off, in the way that you end up with a sharp end. Insert the screw in the wall, leaving around 5mm sticking out. Place the foundation post in the position, make sure its leveled and press it against the wall. You should end up with a clear mark left by the screw. Now, turn the post around and predrill holes in the marked places. Attach the post to the wall and to the base using the construction screws.
Step 9: Putting the Construction Together
You will most likely need one more person for this step.
Firstly put the front support upright, 195cm away from the wall and in line with the foundation posts attached to the wall earlier. Now place one of the 195cm posts at the top of the foundation post and slot the other end into the front frame joint. Secure the construction with screws, making sure you predrill holes to avoid splits or cracks.
Now, take the remaining 3m post and place it at the top of the 195cm posts, against the wall. Secure it to the wall in the same way as the foundation posts.
Step 10: Trimming the Battens Part 1
Take one of the battens and clamp it to the side of the construction, in the way that its` bottom side is just below the horizontal posts as shown in picture 1 & 2. Mark the place where the posts overlap the batten and cut it out. Now you can simply copy the same cut for remaining 5 battens. Do not attach the battens yet.
Step 11: Trimming the Battens Part 2
Set your table saw to around 1cm and cut off the top of each batten. Keep the tops on the side for now. Stain the battens with weatherproof stain.
Step 12: Weatherproofing the Battens
Take the tops you cut off the battens and sand them down.
Bear in mind these boards will be constantly exposed to the elements hence you need to make them as weatherproof as possible. First, apply 2 coats of PVA, letting it dry between the coats. This will seal off the wood, preventing any water soaking in. Next, apply 3 coats of rainproof wood stain, again letting it dry between the coats. Once dried, these boards should feel plastic like when touched.
Step 13: Roof: Part 1
Place the first batten at the very edge of the construction, making sure the sides are flush. Clamp it down for stability. Now, pre-drill 2 holes on each end using the countersink bit. The screws have to be flush or below the batten surface. Secure the batten with 2 screws on each side.
Once the first batten is in place, measure out 60cm from the end of the first batten to the middle of the second batten. Clamp the batten in place and secure it with 2 screws on each side. Next, measure out 60cm from the middle of the second batten to the middle of the third batten. Carry on until all the battens are put in place.
For this particular project, the acrylic sheets are 60cm wide, you might have to adjust the spacing between battens accordingly to your project.
Step 14: Preparing the Acrylic Sheets
Pre-drilling in wood might be important but optional. When it comes to acrylic its a must.
Stack all the sheets on a flat surface making sure all the sides are flush. Now, draw a line alongside, 2 cm away from the edge. Starting from 2 cm away from the end mark points right between the line and the edge. Make a note of the spacing between the points in order to avoid drilling into a screw when putting down the finishing battens. In this case, it was around 20cm.
Now using a metal drill bit, drill and countersink screw holes for mounting screws. Acrylic will crack if you don't!
Step 15: Roof: Part 2
It's time to fit the acrylic!
Firstly apply some silicone to the first two battens. Don't put much as it will float out on the acrylic once you put the mounting screws in. Take the protective film of the acrylic and place it at the top of the battens. Secure the acrylic sheet with the mounting screws. Make sure not to put too much pressure on the acrylic as it will crack!
Next, take one of the tops, cut off from the battens and apply the silicone to its flat side. Place it at the end of the acrylic sheet, covering all the mounting screws. Secure it with the screws in at least 3 places.
TOP TIP: apply some silicone at the top of every screw for extra weather protection.
Follow the same steps to place the second acrylic sheet, the only difference here will be adding extra silicone to fill the gap between the sheets as shown in picture 11. Also when mounting the finishing batten, make sure to place the screws away from the middle. You want to `catch` the top batten, acrylic and the bottom batten with every screw.
Well, that`s it!