Fig. 1: Seals first. Every other step on this page depends on the gaps being closed.
The quick answer
Seal the gaps before you do anything else. Sound crosses an air path almost unimpeded, so a 10mm undercut behaves like a permanent open window and will out-leak the door itself. Fit a bottom seal and EPDM perimeter tape, then add mass to the leaf with MLV and a finish panel. Replacing the door only makes sense once both of those are done.
A door is the weakest element in almost every room. It is thinner than the wall around it, usually hollow, and deliberately fitted with a gap at the bottom for airflow. That combination means the door frequently lets through more sound than the entire wall it sits in, which is also why it is the cheapest place to get a real improvement.
01 /Why the gap matters more than the door
Blocking sound depends on mass, and air has almost none. Wherever there is a continuous air path from one side to the other, sound crosses it essentially unchanged. Upgrading to a heavy solid-core door while leaving the perimeter unsealed is spending a lot of money to fix the smaller half of the problem.
02 /Fitting the seals
- Clean the frame rebate. Remove dust, old adhesive and any previous sealant so the tape bonds properly.
- Fit EPDM perimeter tape. Along the head and both jambs, in the rebate. EPDM keeps its compression through years of opening and closing, where cheap foam strip flattens permanently and stops sealing.
- Fit the bottom seal. Measure the door width, trim to length, and fix to the base of the leaf so it makes contact with the floor when closed.
- Check with a torch. At night, have someone shine a light around the closed door from the other side. Anywhere light passes, sound passes.
03 /Adding mass to the leaf
With the gaps closed, the next constraint is the door itself. A hollow-core leaf has very little mass, so it needs some added.
- SoundBlanket MLV. Bonded to the face of the leaf. Use 2.5mm at STC 30 for bedrooms and offices, 4mm at STC 34 for studios and theatres.
- BassBloc over the MLV. Damps the leaf so it does not resonate once you have made it heavier.
- A finish panel over both. Felt panels, a slat panel or thin HDHMR. MLV and BassBloc are never left exposed on a door any more than on a wall.
04 /Curtains over the doorway
A soundproof curtain hung over the opening adds mass across the whole doorway including the frame, which suits rented properties and internal doorways without a door. Ours is rated STC 29 and reduces up to 80 per cent of outside noise. It works because of the mass loaded vinyl core, not because the fabric is heavy, and it needs to overlap the opening generously to be worth fitting.
05 /When to replace the door
Replacing a hollow-core door with a solid-core one is worth doing when the room is a studio, a home theatre or a bedroom in a shared flat, and when the seals are already in place. As a first step it is poor value, because the gaps will undo most of the benefit. Doing it in the wrong order is the most common reason people spend heavily on a door and hear little change.
Related reading: how door seals reduce sound and heat, and how to soundproof a wall.
06 /Frequently asked questions
What is the first thing to do when soundproofing a door?
Seal the gaps. Fit EPDM perimeter tape around the frame and a bottom seal at the threshold. Sound crosses an air path almost unimpeded, so until the perimeter is closed, nothing else you do to the door will deliver much. It is also the cheapest step by a wide margin.
Is a solid core door worth the money?
Once the seals are fitted, yes, particularly for a studio, theatre or shared flat. As a first step it is poor value, because an unsealed perimeter will undo most of the benefit. A properly sealed hollow door often outperforms an unsealed solid one.
Can I add mass to an existing door instead?
Yes, and it is usually cheaper than replacing it. Bond SoundBlanket MLV to the leaf, add BassBloc over it, and finish with a panel. Check the hinges are rated for the extra weight and consider adding a third, or the door will drop and break the seal.
Do soundproof curtains work over a door?
A curtain with a mass loaded vinyl core does, because it adds mass across the whole opening including the frame. Ours is rated STC 29 and cuts up to 80 per cent of outside noise. A curtain that is merely thick fabric will not, since blocking depends on mass rather than thickness.
Sonit writes about practical soundproofing for Indian homes and workplaces, with a focus on what delivers measurable results at sensible cost.
