Choosing the Best Door for Soundproofing
Now that the skeleton of the inner room had been built, it was time to think of the inner room door. Although I actually spread out this process over several weeks, I will discuss all here for compactness, so you may notice the rest of the build progressing in the background of the pictures. To get the maximum acoustic isolation from the studio, I opted for a fire door, specifically FD30 (i.e. fire rated to 30 minutes). I chose the cheapest solid core wooden fire door I could find, from a company appropriately named DoorDeals.co.uk, and went with the biggest size they had i.e. 36" by 78". The idea here was to not limit the size of gear we would bring into the studio, and I was thinking specifically of kick drums and bass amps.
Here's a picture of the door kit being assembled on the floor to test the measurements:
Required Door Parts
If you have never hung a door before (like I hadn't), there are several key points to understand that make the whole process a lot clearer. I will also say that hanging a door is actually an extremely tricky process (especially without a router!) - don't expect this to work first time. I had a lot of assistance from our friend Doug, and even so it took us a long time to get the door fitted. Anyway, the first point to note is that there are standard sizes of door that most manufacturers will carry , and specifically there are standard heights (i.e. 1981mm, 2040mm etc). This means that you should check what door size you will be installing before building the surrounding framework (i.e. by this point in the build I had already designed my door framework as discussed under Assembling the Stud Walls). You can find custom sizes, but they are inevitably more expensive, and will have a longer lead time.
The next point is that you need to buy several components: the "door leaf" itself is literally just a blank piece of wood. You also need the following components:
- Door handle - clearly, to open the door
- Sash lock - the lock mechanism that has to be recessed inside the door leaf
- Escutcheons - these cover the exposed part of the lock tumbler and hide any screws
- Threshold - this gives an airtight seal on the bottom of the door, using a flexible rubber strip. Here's the one I used - it's crucial to allow for the height of the threshold when planning the door installation.
- Hinges - ball bearing, three or four depending on the weight of the door (three in my case)
- Intumescent strip - this will normally come as part of a fire door kit, and is made up of tiny brushes that seal the gap between the door leaf and door lining. They expand due to heat in the case of fire and slow down the passage of smoke.
- Seals - these are additional extras that can be added later, but they make a huge difference in the door's soundproofing. I used two Stormguard "Around door" Kits: one on each side of the door and these made an incredible difference.
- Most crucially: the door lining/casing - see below
The door lining is made of soft wood and is what the hinges are recessed into - but this is not what actually bares the weight of the door. The door lining itself is fixed onto the studs in the wall that will actually bare the weight - often a double stud to prevent any bending or flexing. Just as a reminder, here's my existing double stud aperture that was ready to accept the door lining:
It's important to note that there is actually a stud running along the door threshold (the bottom of the door). This would get built up even higher eventually, and the reason for this is that the inner door has to swing open inside, meaning that it needs to clear whatever floor is going to be laid inside the room. Therefore, you must ensure that the bottom of the door is definitely going to be higher up than the top of the floor!
Calculating the Door Aperture Size
Although, as I have mentioned, by this point I had already built my aperture, I'll quickly go through this process as it can be quite confusing. I used the following diagram to work out what size my aperture should be (the spacings here are exaggerated for clarity). The darkened part is the door lining, the single hatching is the door itself (the door leaf), and the cross-hatching is the door threshold.
One crucial point not shown on the diagram is that, because it is impossible to position the outermost double studs exactly in the correct position, you need to allow a tolerance of 4mm each side, and position them purposefully 4mm too wide. You will then pack in between the double stud and the door lining using shims to close this gap. This also means that you can get the door lining to be as perfectly straight (millimetre precision is required to prevent the door from catching) and plumb as possible, because you have some wiggle room to play with. This doesn't mean that the double studs shouldn't be as plumb and straight as possible - more time spent getting these perfect will mean much less hassle when installing the door lining.
Installing the Door Lining
The first part of the physical installation was to assemble the door lining, and cut it down to size. When you receive a door kit, the lining is made of three parts: the two sides and the top. All of these parts need to be trimmed to the correct size for your door, making allowances for the gaps and tolerances described in the diagram above. Once this has been achieved, you need to install your door lining into the aperture, packing the gaps to make it perfectly square and plumb. The standard practice to achieve this, is to construct the lining on the floor first, screwing it together. Once the top is screwed to the sides, you then use a tape measure to align the two sides exactly parallel, and use a scrap piece of wood to fix them together. Finally, you use another scrap piece of wood as a corner brace between one of the sides and the top of the lining. These two braces together should hold the door lining perfectly in position. You can see this below: the corner brace is in purple, and the "parallel sides" brace in red
Next, you can lift the whole assembly into the aperture, and pack between the double stud and the lining with
plastic shims as necessary. Once packed, you then screw the lining into the double stud, being careful to have the correct amount of shims at the screw location so as to not distort the lining. Use pairs of screws, and at least pairs of screws per side. These screws need to be as long as possible (I used 120mm) to make sure that the door lining is fixed strongly enough to the stud frame. When doing this, ensure that the hinge side of the door lining is completely plumb at all times - if not you can tighten/loosen the fixing screws as necessary. Here is the white door lining positioned into the aperture:
And here you can see how I actually had to use shims made from plywood one one of my double studs as I had clearly neglected to make it anywhere near plumb enough - be sure to check for plumbness.
Looking at the bottom, you can see that the wooden threshold has been built up, as mentioned before, to ensure that the door will clear the future raised floor. In my case I used three widths of 2by4 stacked on top of each other - here is a closeup for emphasis:
Recessing the Hinges
Next, we had to prepare the door leaf and the door lining ready for hanging. This involved firstly painting the door (I used three coats of gloss white paint), and then recessing the hinges into the side of the door leaf, as well as making recesses in the door lining. Recessing for the hinges involves a lot of precise chisel-work and is extremely time consuming. Here is where a professional would just use a
router and have the job done very quickly, but not wanting to spend the money, we used chisels. I won't describe the chiselling process as there are plenty of guides already out there, but one tip is to actually spend the time sharpening your chisel using a
wetstone - this will make it significantly easier.
I positioned my hinges as follows: one 6" from the top of the door leaf, one in the centre, and one 9" from the bottom of the door leaf. Another tip throughout this process is to mark the hinge side and also the inside and outside (relative to the room) faces of the door leaf: this will prevent any confusion.
Here's the door being prepped, with the hinges fixed in place. Once recessed in, the hinges should be flush with the surface of the door, and not protrude at all.
A top tip for getting the hinge positions to match up exactly on the door lining is to use a wooden baton that is slightly shorter than the door lining height. You can use this to transfer the hinge positions onto from the door itself, ensuring to leave the required gap from the top of the door by making the baton protrude 4cm from the end of the door when transferring the markings to it. You can then transfer these from the baton to the door lining, and they will hopefully line up. Be sure to take one of the hinges off the door and check all three recessed positions on the door lining to be certain that the hinge is flush with the lining.
Hanging the Door
Now we come to actually hanging the door. For this process you will definitely require at least two, if not three people. Essentially, you need to hold the door in position so that the other ends of the hinges line up in the correct places against the door lining. You then need to screw it into position (at least 2/4 screws on each hinge before letting go of the door). I found the best way to do this was to prop up the door on scrap pieces of wood, and one person hold the door while the other person screwed it in. You could also use a product called a
winbag which I purchased later on in the project and is very useful for achieving exact alignment - you can use two to get a door in exactly the right position.
Once the door is on, you may find (like in our case) that it doesn't close - this means taking it down and planing down the offending edges using a
wood plane. After several planing sessions, we finally got it into position as you can see below (note the screw used as a temporary handle - don't close the door without one as you may get stuck!)
You can see all the shavings from the planing on the floor. Next up was cutting the hole for the sash lock (more drilling and chiselling), and attaching the hardware. Again, this is something that is easily googleable so I won't go into detail. To fit the Stormguard threshold under the door I actually had to take the door down again and cut an 8 degree strip off the bottom of the door to make sure that it closed correctly - see the angle in the diagram below (courtesy of Stormguard):
Eventually, after I had installed both sets of
"Around Door" seals, the door was finished. Here is the final product as seen from outside the studio:
