Now we come to perhaps the most time-consuming task of the project: installing the acoustic plasterboard. Overall, (with lots of help from my dad) we installed 85 "Siniat GTEC dB" 4ft by 8ft sheets, each weighing 32.5kg - a total of around 2.8 Tonnes of plasterboard!
This would be done in two phases: initially I would install a double layer on the outer room ceiling framework that I have been discussing. This was Part 1; later on down the line in Part 2, I would build the entire inner room walls and ceilings - more on this later.
The General Process
The key to the plasterboard installation was the purchase of a plasterboard crane, pictured below:
This was absolutely invaluable - it meant that I was able to install ceiling sheets by myself as the crane would keep them in the exact position I wanted while I screwed them in. Even when there were two people doing the job, it would have been impossible without this crane.
The other crucial tool was my impact driver. I have mentioned this before, but the driver, combined with the correct screw head (PH2) meant that I was able to install the ~30 screws needed for each sheet fairly quickly.
(Something I learned during this project, but had previously considered overkill, is the importance of using the correct screwdriver tip. This really does make the difference between a job being easy or taking forever. If, like I wasn't, you aren't aware of the different types, go and find out!)
Cutting Plasterboard
After a lot of trial and error, I found the best way to cut the plasterboard was to use a combination of methods, depending on the size of the section being cut.
For large sections, where there is a strip of more than ~20cm being removed from the main piece:
- Measure up/down from both ends of the board to mark the height of the cut. Use a long (1800mm+) straight edge to join the marks, giving the straight line of the cut. For sections to cut longer than 1800mm, mark the midpoint of the cut and draw the line in two sections.
- Use a Stanley knife to score one side of the plasterboard all along the drawn line. This means running the knife along, cutting the paper face on one side, but not trying to actually slice the plasterboard.
- Simultaneously hit the board on the back of the cut line, while pulling the section to be removed towards the side you are hitting. This should "Snap" the board at the cut, leaving it hanging by the remaining paper face. Keep the cut piece supported at this stage so as not to let the remaining paper face rip.
- Score down the remaining paper "hinge", separating the two pieces.
- You will often be left with a jagged/imperfect edge from your cut that you can then file down using a surform.
For sections to be removed smaller than ~20cm, use a Jig Saw: this takes longer but means that you don't risk breaking the section while snapping it. This is especially true if you need to make a long thin strip: there is absolutely no chance of snapping this kind of piece without breaking it.
Hanging the 1st Skin
Here is a picture of the very first sheet of plasterboard going up:
After about 10 sheets, we worked out a pretty efficient installation process, that would serve us well for the entire build. This went as follows:
- Prepare the necessary tools: an impact driver with a PH2 tip, and plenty of drywall screws. Have both of these ready in a toolbelt - once the board is in position you need to be able to screw it in quickly. You will also need need a laser line, or a pencil and long spirit level.
- Cut the plasterboard to the correct size, measuring the area where it will go to determine this.
- Lower the crane to its lowest height and put the sheet of plasterboard on top, making sure to centre it so that it's balanced (the crane has quite a lot of play in it so that it can adjust to non-level surfaces)
- Move the crane base to roughly the correct position where the sheet needs to be installed
- Begin to wind up the crane to get the board into position. While doing this, walk around the crane to check the position from different angles and confirm the alignment as necessary.
- Continue winding up the crane until the board is pressing lightly against the ceiling: this should hold it still while still allowing for it to be moved slightly
- Make the final adjustments in the position by physically nudging the board (not the crane) into place, before winding up the crane further to secure the board.
- Begin screwing in a couple of the outer screws into the board to fix it in place. Continue doing this all around the perimeter, making a grid of 6 screws longways and 5 screws width ways. Use the centres of the adjacent rafters as the markers for where the perimeter screws should go.
- Position the laser line on the floor on its back so that it draws a line between the perimeter screws on opposing widths of the board. This will then give the line to put the middle 3 screws on - screw these in. (Alternatively, use a straight edge/spirit level and a pencil to draw the line - this is much more fiddly and time consuming because the crane gets in the way).
- Move the laser line to the next row of screws and repeat until the whole board is screwed in.
Here's a few more pictures of the process - this is the fourth board going up:
Slanted Ceiling Sections
As you can see from the image below, our roof had slanted sections at the edges, essentially creating a vaulted ceiling:
These sections were much more complex to install, requiring the following modifications to the process described above:
- This task is much easier as a two person job. Although it is just about possible to do it one-handed, it should be avoided if at all possible.
- You will need to "unlatch" the crane cradle to allow the crane to slope. Then, ensure that the hooks on the crane arms are in position, to stop the board from sliding off when you tilt the crane.
- You should position the board on the crane so that it is balanced, and then manually lift the crane to the required slope - do not try to balance it at a slant.
- One very useful tip we used was to attach a scrap block of 2by4 to the bottom edge of where the plasterboard will go - meaning that the board can sit on this block without sliding down as you manoeuvre it into position. This may seem like extra effort, but it actually saved us a lot of stress.
- Follow the procedure as per regular installation, but ensure you have enough screws in the board before letting go as the crane will want to revert to its balanced, flat position.
Green Glue and the 2nd Skin
Once I had installed the entire first layer of the ceiling plasterboard, it was time to fill all the seams between the boards, to ensure there were no air gaps. For this I used Green Glue Sealant, but this is actually pretty expensive, and in hindsight I think that something like AC50 Acoustic Sealant would have worked completely fine - I used this later on in the project.
Once sealed up, I then proceeded to start installing the second skin of plasterboard, not forgetting to use Green Glue Noise-proofing Compound in between the layers. Here there is no room for cheaper alternatives! I found the best way to do this was by first checking the board was the correct size by winding it up into place, then winding it down a bit to apply the Green Glue in a random pattern, achieving an even coverage. This prevents you from having to take the board down again while stuck with glue if you get it slightly the wrong size/shape.
Green Glue specify that you should use two tubes per 4ft by 8ft sheet, but that one tube has 70% the effectiveness of using two tubes. As I was ordering them in cases of 12, I decided to use just under two tubes per sheet in order to avoid using an extra case, while achieving near maximum performance.
Here's a picture of the green glue being applied:
One final point to note is that when cut-outs in the plasterboard are required for cables or other obstacles, I found it easiest to leave an additional 1cm clearance on all sides of the obstacle to allow for adjustments in the plasterboard without snapping the sides of the cut-out. This extra gap can then be filled with Acoustic Sealant afterwards. It's not worth trying to make the cut-out perfect as this is near impossible to achieve and will inevitably result in board breakages.
And that's it! As I mentioned earlier, plasterboarding in general was probably the most time-consuming phase of the project, so for anyone doing something similar I would definitely recommend working out a process that works for you, as it will save you a lot of time and effort in the long run.