Choosing the Right Sound Insulation to Reduce Roof Noise

Roof noise is a common issue in buildings with thin or uninsulated coverings - if you've ever heard rain hammering on metal sheeted roofs, then you know what we mean.

But, help is at hand! The right sound insulation can cut noise significantly and make spaces like workshops, farm buildings and garden offices feel more usable - read on to find the best options based on your roof material/building type plus important things to know before you buy.

In this article:

Does Thermal Insulation Reduce Sound?

Best sound insulation options by building & roof material:

• Metal Sheets (Workshops, Industrial & Farm Buildings)
• Felt or Bitumen (Garden Buildings)
• Flat Roofs (Garages & Extensions)
• Internal Walls & Floors (Conversions & Flats)

Before you buy:

Will Sound Insulation Block All Noise?

Can you Retrofit Sound Insulation?

Understanding STC and dB Ratings

Is Insulation Easy to Install?

Does Thermal Insulation Reduce Sound?

We see this question a lot - some types of roof insulation designed for heat may help reduce noise - but shouldn’t be relied on for this. If noise reduction is your main goal, look for products sold as acoustic insulation.

In most cases, you can still use both insulation types together - one to keep the heat in, the other to help with sound. But in tight roof spaces or buildings with poor airflow, you might need to be careful how you layer them to avoid damp or ventilation problems.

Choose Your Sound Insulation Based on Roof Material

The roof material and type will often dictate the best acoustic insulation options – below are some of the most common examples we come across.

Corrugated or Box Profile Metal Roofs (Workshops, Industrial, Agricultural Buildings)

Metal is by far the loudest roofing material - especially in large, open buildings. If you're working inside a barn, warehouse, or industrial shed with a corrugated metal roof, noise from rainfall or machinery can be overwhelming.

Common insulation choices:

• PIR/rigid insulation boards installed below the roof deck
• High-density acoustic slabs in ceilings or internal partitions
• Optional: anti-condensation fleece (useful for moisture but not effective for sound on its own)

If retrofitting into an already-built structure, consider installing sound-absorbent ceiling linings or suspended panels where roof-level access is limited.

Felt or Bitumen Roofs (Summerhouses, Garden Rooms)

If your shed is just for storage then you’re not going to be worried about sound insulation. But if you’ve turned it into something more - like a home office, studio or garden room - then noise can quickly become a problem.

Many sheds and garden buildings use felt or bitumen sheet roofing - both of which are lightweight and cost-effective, but offer very little acoustic protection.

These structures are often uninsulated, making them more prone to echo and external noise - especially from rain or nearby activity.

Common insulation choices:

• Rigid insulation boards between roof battens or wall studs
• Natural or acoustic insulation slabs behind internal cladding

Even without a full lining, adding insulation behind OSB or tongue-and-groove panels can noticeably improve noise control and comfort.

Flat Roofs (Garages, Studios, Extensions)

Flat roofs are typically made from bitumen, GRP, or EPDM. They often lack roof voids and can transmit significant rain noise into the room below.

Common insulation choices:

• Rigid insulation boards in a warm roof build-up
• Acoustic wool or slabs between ceiling joists in a cold roof system

If you’re refurbishing an internal ceiling, this is a great opportunity to add sound-reducing materials while improving thermal performance too.

Internal Walls & Floors (Loft Conversions, Flats, Shared Spaces)

Although not part of the roof, unwanted sound between rooms or floors is a common concern in converted lofts, flats, or shared properties.

Common insulation choices:

• Acoustic slabs in stud walls
• Mineral wool or natural batts between joists
• Optional: acoustic underlay or resilient bars under floorboards

Before You Buy: What Else You Need to Know

Sound Insulation Doesn't Mean Soundproof

Even high-performance insulation won’t block all noise. And you may get even worse results if:

• There are gaps, vents or poor joins
• There’s no ceiling layer or interior lining

If you need near-total isolation (e.g. in a music room or sensitive workspace), you’ll need to combine insulation with airtight sealing, dense linings and sometimes suspended acoustic barriers.

Can You Retrofit Sound Insulation?

Often, yes - especially in buildings with exposed roof structures, like barns, workshops, or industrial units.

If your roof has open joists or purlins on the inside (a typical cold roof setup), you can usually fit insulation internally by adding acoustic slabs or rolls between the structural elements, then boarding over if needed.

Warm roofs (where insulation sits on top of a solid deck) are harder to retrofit without removing the roof layers - more common in flat roofs or metal-clad units. These may need a full re-roof to add proper insulation.

Be Careful with Ventilation

In any roof - especially pitched or cold roofs - maintaining airflow is crucial. Poorly fitted insulation can block essential ventilation routes, leading to moisture build-up, condensation, and long-term damage.

To avoid problems:

• Never block eaves or ridge vents (where air flows in and out)
• Maintain a clear air gap between insulation and the underside of the roof
• Use breathable materials if the roof requires vapour movement
• Follow correct build-up advice based on your roof type

Even if full retrofitting isn’t possible, adding internal linings with acoustic slabs or boards can still reduce noise - especially in timber garden rooms, workshops or converted spaces.

Understanding STC and dB Ratings

If noise is your main concern, pay attention to acoustic performance figures in product specs.

• STC (Sound Transmission Class): how well a material blocks airborne noise like voices or traffic
   → Higher STC = better sound isolation
• dB Reduction: overall sound dampening across frequency ranges
   → Higher dB = more noticeable noise reduction

These numbers aren’t always listed, but where they are, they’re a useful comparison point between similar products.

Is it Easy to Install?

This will depend on the material and the roof structure but typically many insulation types - especially wool - are DIY-friendly with basic tools.

General Tips:

• Always wear PPE when handling fibrous materials
• Cut neatly to avoid gaps - air leaks reduce performance
• For flat roofs or large ceilings, a second pair of hands is useful
• Some builds (like warm roofs) may require professional fitting

Where to next?

There’s no one-size-fits-all solution - and no single product can completely silence a noisy roof. But with the right approach, you can significantly reduce noise in any structure, from a garden shed to a commercial warehouse.

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