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How not to soundproof your garage roof

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As a soundproofing company we are often contacted by clients looking to soundproof a garage.  Whether for a music room, home office or a man cave many clients are looking to make noise without disturbing others.


Unfortunately, we also see a number of poor clients who had a builder attempt to soundproof their garage. Resulting in a failed soundproofing attempt or even worse black toxic mould lurking in their garage.

builders attempt at soundproofing garden room

The roof

Most garages have a flat roof.  A flat roof needs to be either a warm roof with rigid celotex, Kingspan type insulation or a cold roof which has open rafters and is breathable with airflow. Either of these approaches are to prevent mould and keep the room below warm. But both are terrible for sound transmission.

A flat roof on any outbuilding needs to be airtight without the use of celotex or Kingspan or any other polyurethane type insulation that does nothing for noise.

When soundproofing a garage with the intension to use it throughout the day, the flat roof needs to take into account condensation.

The warm air will keep rising through most insulation products and when it hits that cold spot, it will turn into water to form condensation. This condensation is likely to gather on the underside of the plywood beneath your rubber or felt roof. When you have condensation you have mould, which turns into toxic mould.

What not to do

The picture above is a builders attempt at soundproofing a practice room with acoustic insulation and 12.5mm blue sound bloc board. This is how not to soundproof your garage roof. The plywood we exposed behind the acoustic insulation was covered in toxic mould.

The solution

When designing and building soundproof practice rooms and garages, the roof is one of the most important parts.  The picture below is a garden studio, designed by Jim Prior the founder of Quietco. The NFRC (National Federation of Roofing Contractors) approved and praised the design and it has three 0% condensation risk assessments approved by two major insulation companies.  It is made up of 10-inch rafters and our TPS80C trademark ceiling system with a beautiful meadow grass sedum roof on the top.  Read our blog soundproofed studio in your garden to see more.


If you are looking to soundproof your garage make sure you treat the roof correctly and do not inadvertently end up with black toxic mould.

Read our blog on soundproofing a garage to see how we transformed our clients garage into a music room for his drums.

Give us a call on 01926 658 638 and we would be happy to help you with your project.

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