Temporarily soundproofing doorway

[Theo Markettos]

We have a disused doorway, on one side of which is a bed and the other side of which is the food preparation surface in the kitchen. The door remains in place, but is hemmed in by the kitchen units. It's a single skin plywood panel door, so the panels are only a few millimetres thick.

All kinds of kitchen noises can be heard perfectly clearly through the door, which is annoying. Blocking up the doorway permanently sadly isn't an option. Without changing the door or modifying the fabric (so in a way that can be installed and removed without marks) how might the soundproofing of this doorway be increased?

There's plenty of space thickness available on the kitchen side, so I thought about placing a second skin in front, perhaps another old door, and then filling the gap with something. Thermal insulation (mineral) wool is a possibility, but how good is this for sound rather than heat insulation? As the noise is primarily low frequencies I imagine I want something that's layered but denser than fluffy foam (like books rather than candyfloss). (And, as I can't seal it, loose fibreglass floating round the kitchen isn't so great)

Any ideas?

Thanks Theo

[sm_jamieson]

You can get high density mineral wool designed for acoustic insulation. Simon.

[Dave H.]

You can get high density mineral wool designed for acoustic insulation. Simon.

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Hi Theo, Another factor in good soundproofing is mass, particularly for low frequencies, so it's worth making the second skin from something fairly heavy, e.g. 12 or 18mm ply/OSB/MDF with a couple of layers of plasterboard screwed on one or both sides.

If you can make the skin isolated from the existing door (with as big an air-gap as possible between the door and the new skin) it will help, so perhaps a frame of 2x1 timber that fits the door aperture with a slight gap and foam rubber or similar making up the difference, the ply and plasterboard fixed to the 2x1 frame? If you're *serious* about noise reduction, Google for the BBC's "soundproof door", but be prepared to strengthen the hinges... and the doorframe!

Sealing the cracks around the door is a very important step, the foam rubber / weatherstripping should run around all four edges, good advice I heard once was "think of it as a submarine and stop up all the cracks"!

HTH, Dave H.

[Bren]

Agree about the plasterboard - 3 or 4 layers preferably. The link below makes interesting reading -

[Theo Markettos]

prefilled with plasterboard: saves me having to construct the layering myself, though whether it's feasible for me to cut one down to fit the inner doorframe dimensions I'm not sure. (The fire-door-ness is also useful too, in case there's a kitchen fire)

If I screw things into the door (eg hooks) is that likely to damage the soundproofing a lot?

Theo

[RobertL]

Could you unscrew the door and store it, so you can put it back later? You could then fix two double plasterboard planels inside the frame with rockwool in between. As others have said, you need mass to stop the low frequencies and fibre filling to stop the highs. You need good caulking around the edges and you must have no mechanical link between the two heavy panels other than along the edges.

Perhaps you could bolt the two panels together along the edges so as to grip the doorframe but without damaging it.

Robert

[Bren]

I don't think it would make much difference to the soundproofing unless you completely bridge the space between the front and back of the door.

[js.b1]

Double layers of cement board?

One issue is the architrave and door frame. You need to pull an architrave off and fill it with expanding foam (acoustic foam?) because otherwise you have a very easy path for sound to "slip around" whatever you do. Architrave wood of 2x 19mm, then an air gap pretty much.

Likewise I assume the door is not a stud wall - no point creating a "super door" if the rest of the wall lets it down.

[Theo Markettos]

That's possible. I also notice that the access to the kitchen side of the door is constricted (units in the way) so getting in panels could be tricky. I'll have to grab a bit of wood and test the angles.

As I can't damage the fabric, pulling the architrave off isn't an option :( I think I'm going to have to live with leakage around the sides. Apart from conduction through the architrave wood, is there typically an air gap between it and the end of the wall?

It's loadbearing, so I'm pretty sure it isn't stud. There's also a chimney in it (opening only into the bedroom), so I'm not sure what that's doing for the acoustics (other than piping down sounds of pigeons sitting on the chimney pot).

Theo

[js.b1]

Hole in brick wall. Fit door frame loosely in hole. Fit wooden wedges between wall & frame and align. Screw through frame into brick wall with frame anchors.

Thus there tends to be a gap between the door frame & wall, on older houses it can be quite large (0.75") whereas on modern it is most likely somewhat smaller.

A more direct noise route is of course around the door - draught excluder can help considerably.