I'm gathering materials to add mass to the room 1 door. The door is an FD30 rated fire door with a solid ceramic core. It has a gasket round the perimeter, and I've already installed a drop down seal at the bottom. I estimate the weight is about 40kg, to be verified on scales next time I remove it.
Since the wall has already been improved, the current attenuation is represented by the red line on the following graph. The door is currently a weak link in sound transmission chain, offering less attenuation than the wall, particularly between 100Hz and 2000Hz By improving the door, my goal is to move the theoretical attenuation of the combined wall and door from the red line to the green one.
So far I've acquired the following;
- 18mm plywood @ 11.5 kg/m2
- 5 kg/m2 MLV, enough for several layers
- Overhead door closer rated at 100kg with "fully adjustable variable power with latching action, backcheck & delayed action"
- Heavy duty ball bearing hinges rated up to 120kg
I have ordered some better weatherstripping to evaluate. As detailed earlier in this thread, I've already strengthened the stud work around the door frame.
In an ideal world I'd build the door like Rod Gervais super door, with sufficient MLV sandwiched between the door and the 18mm ply. This is applied to the push side of the door. Unfortunately this option is not available to me as the door has this lovely paneled finish I'd like to retain on the push side. It's the side that opens into our landing area, so has to look matched and proper with the other doors in the house.
The door pull side faces into the studio, and will be almost 100% covered with absorption anyway, so it's not essential to retain the door panels there. So that's the side I'll add the mass to. Fortunately the door frame & architrave will permit a "bank vault" style seal to be applied by making the added plywood a little larger than the door. This will work on the top and latch side of the door, but not on the hinge side as the overhang would foul on the hinges. I figure this isn't such a big deal though, as the compression on the gaskets along that side of the door will give an excellent seal anyway.
The door is thinner where the face panels are recessed, so I'll fill those in with thin strips of MLV and insulation padding to make the mass even across the door.
So, it will go from the current door profile that looks like this;
- current door profile.png (25.04 KiB) Viewed 6190 times
- current door profile.png (25.04 KiB) Viewed 6190 times
to this. This has two layers of MLV with a depth of 4mm between the door and 18mm plywood.
I'll install appropriate gaskets wherever possible, and perhaps another drop seal on the push side face. Two layers of MLV should bring the door to about 80kg total mass, around 49 kg/m2.
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Does this plan seem sane?
There are currently three fire door hinges, one near the top, one near the bottom, and another in the middle. I'll replace these with the 120kg rated ones I've bought. Will it be necessary to fit another one between the top and middle as I've seen on some other heavy doors?
Cheers!
Jennifer