Category Archives: Sound Proofing

Plaster Board Finish

Wall Finishing and Fire Compartmentalisation

Sanding

The golden rule is-avoid sanding as much as possible by ensuring that the knife finish is smooth at the edges and as close to a final finish as possible.  If one had to do this manually with a sanding block and pole it would be a tough job.

Thankfully over the years people have been improving the tools. I was lucky enough that the builder loaned me his sanding machine.  I just needed a hoover to manage the dust which was picked up free on the free cycle web site. The sanding machine looks like the following:

Sanding Machine
Flex WS 702VEA

Even though the above Flex machine makes the job easier and faster it still is a physical job especially when working overhead.  The hoover was not designed for the above but it worked out OK once the bag and filters were cleaned regularly.

I would suggest safety glasses when working overhead and a face mask at all times.

Technique for Sanding Used

The joints had a second coat of plaster and then a touch up coat was used to remove any edges and at the same time look for and fix any imperfections on the butt finishes (where two boards are joined with no taper edge) or tapered edges. USG 3 Sheetrock (see previous blog) was used for the second and third touch up coat.   I would not recommend the Gyproc joint filler for the second and third coat as it is primarily used for the first coat and it does a great job. When dry the finish is very hard and it would be difficult to sand. There is a Gyproc pro finisher but I found the Sheetrock product very economical and easy to work with for the second and third coat compared to other options.

I used a 150 grit sand paper on the Flex machine and left it at speed 4.   I was expecting that the sand paper would get blocked up but this did not happen. I was advised and found it very important to sand the edges of the joints and ensure that one does not stay too long on the edges as the paper on the plaster board could be damaged.  A light sand in the centre of the joint is how I finished each joint.

Sanding Joint Filler
Edge Sanding of Plasterboard

 

 

 

 

 

 

 

 

 

 

 

I also found it necessary to manually inspect the wall after the electric sander as one is too far away from the wall with the sander to spot imperfections. I made up a hand sanding block for this with a wood fibre board angled to get into corners.

Home Made Sanding Block

 

 

 

 

 

 

 

 

 

 

 

The angled  wood fibre board worked out better for me than dedicated sanding blocks and I used a pre-used sanding disc from the electric sander.

Self Build
Wood Fibre Board as a sanding block.

 

 

 

 

 

 

 

 

 

 

 

Plasterboard Corners

I experimented with the wall corner finishes on whether a sharp edge or rounded corners worked out better. The sharp edges looked like that shown in the top image below and the rounded corner is the image below that. If I was doing it all again I would use the rounded corners as I feel it looks better.

Plasterboard corner finish straight edge. Note dust still on one wall.

 

 

Rounded Corner

Fire Compartmentalisation

Typically with internal wooden stud walls there may be gaps between rooms at floor level or vertically. For this reason one may want to ensure that fire compartmentalisation is addressed (a previous blog covered this in detail). In order to do this I have chosen a B1 rated fire foam for the floor gaps. It also has a secondary benefit of reducing sound travel between rooms at these gaps. The foam I used was Olive PU-476.  The price varies and the best value I found in Ireland was at National Seal Systems in Dublin. I also bought intumescent water based fire sealer for small gaps around the edges of the distribution board and vertical uprights where one partition  meets another.

Self Build

 

 

 

 

 

 

 

 

 

 

Acoustic and Fire Design

Fire and Acoustic Isolation

Having recently come across a best practice guide for Electrical installations and their effect on the fire performance of buildings I have decided to change  the approach to the fire/acoustic isolation between rooms. I will now install Rockwool flexi 50mm in the 100mm partition walls and Rockwool flexi 100mm in the 140mm partition walls .

Electrics before insulation
Partition before Insulation with Wiring
Rockwool
Partition wall with Rockwool installed

From an acoustic perspective I was advised that it is better to install the Rockwool in the centre of the partitions rather than touching one or other side of the plasterboard as this limits the sound transfer.

The Electrical Safety Council best practice guide deals with Electrical installations and their impact on the fire performance of Domestic premises at this link when one is building a home. A summary is as follows but the full document is worth reading for any self builder.

  • Fire containment in the event of a fire
  • The need to prevent fire from passing through holes in all elements whether solid or lightweight is addressed.
  • Electrical Equipment is identified that has a direct and significant influence on the fire performance of an element.
  • Partial Penetrations –those that reduce the fire performance of part of the wall/ceiling or floor.
    Full Penetrations-such as ducts and fans that go through both elements of a wall/ceiling/floor.

 

Internal Partitions and Soundproofing

Partitions

The internal partitions were recently installed.

Passsive House
Passive House Build

Solutions now need to be planned to minimise noise between some of the rooms. The effort one puts into this needs to be balanced with the fact that there will be a 10mm gap under the doors for the air to circulate when using heat recovery.  I might install a supply and extract outlet in the important rooms in order to minimise noise. How much noise will travel in these ducts is for another day.

Proposed Method

All the air gaps (wall to floor gaps, sockets, switches and service cavity) around the partitions need to be filled.

I will fill the ceiling and wall gaps of the service cavity with rockwool (see below).Perimiter Insulation

The method to reduce the noise I am considering for the walls is a product that uses a dampening material between two sheets of plasterboard. One of these products is Green glue and the other is Quietglue pro.  The solution appears to perform very well and I feel it is the simplest method. I plan to take  extra measures between the study and living room such as including rigid insulation (Rockwool RWA45 but I note the insulation costs €37 in Ireland and £13 in England (more research required) .

The performance values used to measure the sound proofing in America is called STC (Sound Transmission Class) and is measured in decibels (dB) against 16 different frequencies. If the sound level was 80dB in one room and the measured sound level in the other room had a  STC of 37dB the sound reduction would have a figure of STC 43.

STC only calculates the dB levels down to a frequency of 125 Hz. One needs to be aware that low frequency sound can exist from drums , traffic and an additional solution may be required.

The performance test data of the Green Glue can be found here

If one was to use one layer of green glue with an extra sheet of plasterboard one would achieve a STC value of 43 for a 4 inch wooden stud wall with 24 inch centres.

If one was to use 4 inch block this would achieve a STC of 44.

Filling a standard 4 inch wooden stud wall (with 16 inch stud spacings) with fibreglass and using plasterboard on each side achieves a STC of around 39. If one increased the stud spacing to 24 inches and filled it with insulation then the STC value would be 46.

If one was to leave out the insulation on a standard wooden stud wall one would achieve a STC value of 34.

A good source of information on sound proofing is at USG (Gypsum)

Robust Airtightness

In locations where the partitions meet the airtight membrane I am using Solitex Plus (see below -blue material). If one used only the airtight membrane it can easily be damaged.

Passive house
Solitex Plus