Category Archives: Partitions

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

 

 

 

 

 

 

 

 

 

 

Plaster Board Update

Plastering – Taping and Jointing. Tools and Lessons Learnt.

I finally completed installation of the plasterboard with the help of the mechanical plasterboard lifter and I have now just started taping and jointing. I decided on the international method of finishing the plasterboard rather than the Irish method ( see previous blog https://selfbuild.blog/2016/07/10/plaster-board-plan/) . If one is determined to use the traditional Irish method of wet plastering the whole wall I would still tape the joints with paper tape rather than the nylon/plastic mesh. The paper tape ensures the fire proof rating and from my research it is a stronger joint.

Below is an image of what it looks like when one applies the first joint filler tape coat. There are two to three more coats of plaster filler/compound required to hide the joints completely and some sanding.

Joint Taping
taping joints

I tried different methods and tools such as using a hawk instead of a mud pan to hold the plaster. For me the 12 inch mud pan worked out the best .

 

 

 

 

 

 

The tape dispenser is more important than I thought. The unit I purchased was a good design on paper but not very practical. If I was purchasing a unit again I would go for the steel design . The current model I am using is as shown below.

 

 

 

 

 

 

For ones own safety one must be able to roll the paper up  after taping the joint as the hanging paper can  become a trip hazard when moving around.  I would try this steel one instead if I was starting again (see below).

 

 

 

Another item is a glove for the knife hand. If one is working with the filler for a few days I have found it to be very rough on the hands. Over time the skin will toughen up I suppose.

Beads

There are two main types for corner beads used for edge finishing . The steel micro edging (first image below) or the paper tape reinforced with steel (second image). I found it easier to use the steel micro edging rather than the  reinforced tape edging. I tried a few methods of attaching the mesh and I settled for first applying the compound and using a few stainless steel staples(the standard ones are not stainless steel) to fix it securely while applying a finishing coat to fully bed it in. Note-ensure that one fully cleans the stapler after doing this.

 

 

 

 

The steel micro edging I feel is a better method to finish an edge and it is easier to sand and clean when applying wet filler.

Another idea that I did not get to try but it looks interesting is the use of pre-formed corner / edges  using plasterboard. This avoids the use of beads and it is called the ZaapSystem from Prodar.

The reinforced tape comes into its own when one needs to tape two walls that meet with slight angles. The price of this varies from €15 to €30 for the same length.

 

 

 

 

 

 

 

Fillers

I tried different fillers/joint compounds . Gyproc dry wall filler (it comes in a bag and is quick setting ). One mixes it with water and it requires the use an electric mixer to prepare it. This bag works out fairly economical but the time spent mixing, the dust, washing out the bucket every hour or so is very time consuming. Another disadvantage is that it sets very fast and is very hard to sand afterwards. The colour is also a disadvantage as it does not blend well with the plasterboard. An advantage is that it works out well when fixing the steel micro mesh.

The next product I tried is the Gyproc bucket version (pre-mixed) 15 litre. This is easy to work with but again it is a white finish which will make it harder to blend into the wall and will require more painting. It is also very expensive.

The best product I found and the most economical for the joint is supplied by Greenspan called USG plus 3 (it is an American product) and it comes in a 17 litre tub. It has the best colour blend for the board, it gives a finer finish, and is easy to sand. It does require a small amount of water to be added to make it extra easy to work with (this makes it go a bit further).

 

 

 

 

Tips

  • When applying filler near floor level increase the width of the filler to ensure that any skirting board lies flush against the plasterboard.

 

 

 

    • Use paper rather than plastic mesh for a stronger and fire safe joint.
    • Practise filing joints in a non critical area such as behind future wardrobes, en-suite or storage room etc.
    • Have a rag /clothe clipped to your belt to wipe away any dried plaster pieces before they get caught in the fresh new compound and leave streaks.
    • Use the 4 inch knife to remove any dried plaster compound or for checking  screw heights. The other knives need to be protected from any edge damage or you will get streaking.
    • If the corner is less than 90 degrees I found it difficult to get a clean edge as there was limited space. In this case I made a finishing tool cut to the angle of the wall and ceiling with a rigid plastic cover to give a smooth surface.
Plastering
Corner Plaster finishing
  • I found it helpful to have the 4 inch knife stuck to the pan with a magnet. It saves some time bending down or climbing down the ladder to get it when using  two other knifes. I typically would have the 6 inch knife for finishing edges and either the 10 inch or 12 inch for finishing butt or tapered joints. The 10 inch stayed in the back pocket .
4 inch Knife stuck to pan
Magnet on pan

 

 

 

 

 

 

 

 

 

 

 

 

  • Fully clean the knifes and dry them at the end of the day.
  • You will notice the difference between good quality knives and low cost knives.
  • If a knife should get damaged by a screw head I used a sharpening stone to repair it.

plastering repair

 

 

 

 

 

  • In order to minimise sanding sometimes it is better to re-apply another filler coat to get a perfect finish.
  • For corners I found it easier to use a corner knife (90 degree angle) and feather the edges with the 10 inch knife.
  • Use the 4 inch knife to clean away any small hardened plaster bumps before starting  the second coat.

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.

 

Plaster Board Plan

Plaster Board Installation

I plan to install as much of the plaster board by myself. There are different techniques for completing the finish. I note that one must use paper between the joints in order to maintain the fire proof rating and the paper jointing material provides superior resistance to cracking. (see www. Gyproc.ie Jointing document)

It appears that the plastic mesh is not to be used even though it is popular.

When the boards are in place there is a special plaster joint coating for the first two coats and a different jointing plaster is used for finishing the joint.

It appears that we will not be able to plaster finish the complete boards as the humidity level in too low and there is a risk that a coat of plaster may crack during the drying process.

For the bathrooms areas around the shower I plan to use magnesium board or cement board as it offers superior water proofing.

Applying the plaster to the joints.

Below are a few videos I located in order to watch and learn from the professionals.

More details that may help

Tools

An important tool if one is doing the plaster board oneself is a plaster board lifter .

Some of these have height restrictions . Some are very professional and expensive and some are low cost. They vary between €150 and €1000.

Some plaster board web sites that I located to date are

http://shop.wiltec.info/product_info.php/info/p4801_XXL-Drywall-Lift—Sheetrock-Lifter-Panel-Hoist.html

One that I will be not using

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