Soundproofing A Semi Detached House: The Complete Guide

Living in a semi-detached house comes with its share of challenges, especially when it comes to noise from neighbors. Sharing a wall means you’re bound to hear some level of noise transmission between units. This guide will teach you everything you need to know about soundproofing a semi-detached house, from identifying noise issues to DIY and professional solutions.

What Is a Semi-Detached House?

A semi-detached house, also known as a duplex, is a dwelling that shares one common wall with the neighboring property. Unlike detached houses, semi-detached units are built side-by-side and adjoined by a party wall in between.

Semi-detached houses became popular in the late 19th century as a more affordable option than detached homes. They continue to provide a compromise between cost and privacy today.

Sharing a wall does mean some noise transfer is inevitable in a semi-detached house. But with the right soundproofing techniques, you can block unwanted noises from next door.

Want to know if your landlord is responsible for soundproofing your rental? I’ve written an article on Are Landlords Responsible For Soundproofing that explains the laws and your rights as a tenant

Common Noise Problems in Semi-Detached Houses

Several issues can lead to excessive noise transmission between semi-detached homes:

  • Thin walls – Older units may have single brick walls or poorly insulated drywall. This allows voices, music, footsteps, etc. to be clearly audible.
  • Shared floor joists – Most noise complaints in semi-detached houses are due to floor vibrations traveling through attached joists.
  • No wall cavity – Pre-1920s buildings often lack an insulated cavity in the party wall, allowing noise to pass directly through.
  • Plasterboarding – Dot and dab plasterboards severely reduce sound insulation between units.
  • Air gaps – Gaps around wiring, pipes, joists, and outlets allow noise to leak through openings.
  • Flanking – Sound travels via ceilings, floors, and flanking walls, bypassing your soundproofing efforts.

Dealing with noisy neighbors is never fun. The good news is there are solutions available to substantially reduce noise in a semi-detached house, which we’ll explore next.

Got squeaky floors driving you and the downstairs neighbors crazy? Read my article on Are Landlords Responsible For Fixing Squeaky Floors? to find out if your landlord must fix them.

How To Soundproof a Semi-Detached House

You essentially need to block noise transfer paths between the units. This involves a two pronged approach:

1. Soundproof the party wall – Add mass and stiffness to stop noise radiating through the shared wall.

2. Address flanking paths – Treat the floors, ceilings, and other connected surfaces noise can travel through.

Completely eliminating noise from neighbors isn’t realistic. But you can reduce disturbances to comfortable levels with proper soundproofing techniques.

Soundproofing Products and Materials

Various soundproofing materials are available to reduce noise transmitting through walls, floors, and ceilings:

  • Green glue – Constrained layer damping compound applied between drywall layers.
  • Mass loaded vinyl (MLV) – Heavy, limp vinyl sheets containing barium salts.
  • Acoustic caulk – Sealant for filling gaps and blocking sound leaks.
  • Acoustic putty pads – Pliable pads placed under wall plates, electrical outlets, etc.
  • Soundproof drywall – Multi-layer drywall with viscoelastic glue.
  • Insulation – Absorbs noise and dampens vibrations when installed in cavities.
  • Resilient channels – Metal furring strips that clip walls/ceilings away from studs.
  • Sound clips – Isolate finish surfaces from structure using neoprene.

DIY Soundproofing Tips

Here are some simple DIY steps you can take to reduce noise in a semi-detached home:

  • Caulk and seal all cracks, crevices, and openings with acoustic sealant.
  • Apply acoustic putty pads around outlets and switches on party walls.
  • Install solid core doors with perimeter seals to bedrooms and bathrooms.
  • Lay down carpets and rugs to help absorb airborne noises.
  • Use soundproof curtains over windows to block outside noise.
  • Fill wall cavities with insulation like rock wool or fiberglass.
  • Hang acoustic panels and bass traps to absorb sound reverberation.

These quick fixes provide noise relief by sealing and damping sound leaks. But more intensive solutions are required to substantially reduce loud neighbors and footfall noise.

Fed up with loud stomping from upstairs neighbors? My article Upstairs neighbor Stomping covers ways to muffle impact noise from above.

Advanced Soundproofing Solutions

The following steps will effectively minimize noise transfer between semi-detached units:

1. Disconnect Shared Floor Joists

Impact noises like footsteps can travel through connected joists. Decoupling the floor framing from the party wall is the best way to prevent this flanking issue.

There are several options:

  • Cut the joists so they no longer embed into the adjoining wall. Refasten them independently to the perimeter walls using joist hangers.
  • Install a resilient sound clip system that suspends the joists away from the party wall using neoprene isolators.
  • Construct a floating floor on sleepers or a screed base that is detached from the existing floor.

Sealing any air gaps around joists in the party wall is also important for blocking sound leaks.

2. Soundproof the Party Wall

The party wall likely requires substantial upgrades to achieve meaningful noise reduction between units.

For masonry walls, applying a new isolated drywall layer is recommended:

  • Install resilient channels horizontally across wall studs.
  • Attach 2-3 layers of 5⁄8” drywall to the channels using acoustical sealant and staggered seams.
  • Fill the wall cavity with sound batt insulation.
  • Seal perimeter edges with acoustic caulk.

This achieves both mass and an air gap to damp noise through the brick wall.

For existing insulated drywall party walls, adding mass is the priority:

  • Apply 1-2 layers of soundproof drywall, such as QuietRock, glued with Green Glue.
  • Install a new staggered stud wall (double-stud wall) filled with insulation.
  • Consider a double-wall frame packed with insulation for severely noisy situations.

The more mass, the better. Just adding extra drywall can make a noticeable difference.

3. Upgrade Flanking Surfaces

It’s vital to address connected ceilings, walls, and floors to prevent flanking noise transmission.

For ceilings attached to the party wall:

  • Install resilient channels before re-hanging drywall.
  • Use double layers of drywall glued with Green Glue.
  • Blow in dense sound insulation.

For interior window walls:

  • Apply mass loaded vinyl (MLV) or limp soundproofing membrane.
  • Build a new decoupled stud wall with staggered studs.
  • Install a double-stud wall with insulation.

For floors, adding a soundproofing underlayment or floating floor will provide acoustic isolation.

By blocking all noise paths, your efforts on the party wall will be effective. Consult an acoustical professional to identify all flanking issues.

Can You Hear Your Neighbor in a Semi Attached House?

The short answer is yes, you will likely hear your neighbors in a semi-attached house to some degree. Voices, music, footsteps, doors slamming, and other noises can be audible through the adjoining wall.

Several factors contribute to noise transfer in semi-detached homes:

  • Thin walls with inadequate insulation allow sound to pass directly through. Older homes often have single brick walls.
  • Shared floor joists transmit impact noise like footsteps as vibrations travel through the connected framing.
  • Plasterboard walls, common in renovated homes, offer very little sound insulation.
  • Gaps around wiring, pipes, outlets, etc. let noise leak through openings in the wall.
  • Flanking transmission occurs when sound travels through ceilings, floors, and flanking walls.

The amount of noise also depends on your neighbor’s habits. Loud music or heavy foot traffic will be more noticeable. Bedrooms are often quieter as the upstairs wall tends to be thicker.

While some neighbor noise is inevitable, there are ways to substantially reduce sound transmission through walls, floors, and ceilings in a semi-detached home. With proper soundproofing, you can block noises like voices, TVs, and footsteps to comfortable levels. But complete silence between units is next to impossible.

So in summary, the shared wall does allow higher noise levels between neighbors. But smart soundproofing techniques can help minimize disturbances and improve privacy.

Want to prevent your neighbors from overhearing private conversations? I’ve written a helpful article on Can Your Neighbors Hear You Talking with solutions.

Also, read my article How To Soundproof Wall From Noisy Neighbor for DIY techniques to reduce noise transfer through walls.

Hiring a Soundproofing Contractor

Tackling an extensive soundproofing project in a semi-detached house is complex. You’ll get far superior results by hiring a professional contractor rather than DIYing it.

When to Consult a Professional

DIY soundproofing may help, but for extensive noise issues, it’s best to hire an expert:

  • For impact noises like heavy footsteps, consider decoupling shared floors which is complex.
  • If your DIY efforts fail to effectively reduce noise to satisfactory levels.
  • In older homes with no insulation, major renovations may be required.
  • To identify actual noise flanking paths, rather than guessing.
  • For major renovations like building new decoupled walls, disassembling surfaces, etc.
  • If you want acoustic testing done before and after soundproofing.
  • For a custom engineered solution tailored your property’s needs.
  • For better overall results since professionals are experienced in sound transmission.
  • To save time and effort with a contractor handling the entire project.

In many cases, soundproofing a semi-detached home requires extensive work best left to the experts. Their added expertise can make a difference in reaching your noise reduction goals.

Look for an experienced acoustical firm that provides the following services:

  • Site evaluation – Inspect your property to identify noise issues.
  • Acoustic testing – Measure sound transmission levels before and after.
  • Problem diagnosis – Pinpoint actual noise transfer paths, not guesses.
  • Custom plans – Tailor the soundproofing solution to your needs.
  • Skilled installation – Certified staff who know how to do it right.
  • Flanking control – Full encapsulation, not just the party wall.
  • Performance warranty – Guarantee on achieving noise reduction goals.

A proper soundproofing job in a semi-detached house costs $4,000 to $12,000 depending on the scope. This investment can improve living conditions and resale value.

Consult reputable firms and get quotes to find the best contractor for your project.


Living in a noisy semi-detached house can quickly become frustrating and stressful. Thankfully, applying soundproofing techniques can drastically reduce noise passing through shared walls and connected surfaces.

With the right combination of sound blocking products, noise flanking methods, and professional installation, you can transform even the loudest attached home into a peaceful sanctuary. Just be prepared for an intensive and costly process – soundproofing a semi is not easy. But the investment will be worthwhile.

Need to block annoying noise from your neighbor’s yard? Check out How To Block Noise From Neighbors Yard for ideas on reducing outdoor noises

Key Takeaways

  • Semi-detached houses inherently transmit more noise through shared walls and connected surfaces.
  • Blocking noise flanking paths is just as important as soundproofing the party wall itself.
  • Disconnecting floor joists and adding mass to walls provides the best noise reduction.
  • Hiring an acoustic contractor experienced in semi-detached buildings is recommended.
  • Effective soundproofing solutions are available to minimize noises from neighbors.

Frequently Asked Questions

Can You Completely Soundproof a Semi-Detached House?

Completely soundproofing a semi-detached house is impossible. Applying soundproofing to the party wall, floors, and other paths can reduce noise substantially, usually by 75-90%. This minimizes disturbances to reasonable levels.

Does Adding a Drywall Layer Help in a Semi-Detached House?

Adding an extra layer of drywall on the party wall provides a little noise relief. Greater benefits are achieved by using acoustical drywall, sealing surfaces, and decoupling walls. But an extra drywall layer is still better than nothing.

Should You Insulate the Party Wall Cavity?

If there is an air gap in the party wall, fill it with insulation like rock wool or Roxul. The insulation dampens noise vibration and absorption. Just don’t pack it too tightly. Leave 1-2″ for an air pocket.

How Thick Should the Party Wall Be?

Building standards require a 10-12 inch party wall, but thicker is better for soundproofing. Adding drywall layers can make the wall 15-25 inches thick, greatly improving noise blocking.

Can New Carpet Reduce Noise in a Semi-Detached House?

Carpet muffles airborne noise but isn’t very effective for impact noise through floors/walls. Proper sound insulation needs to be installed under the carpet too. Underpad also helps reduce noise.


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