
How to joint GIB plasterboard
Many people simply remove wallpaper, apply a thin layer of plaster to the wall (this is known as skim coating) and then re-paint the wall. Often the wall cracks and the surface is compromised within a short time.
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Many people simply remove wallpaper, apply a thin layer of plaster to the wall (this is known as skim coating) and then re-paint the wall. Often the wall cracks and the surface is compromised within a short time.
Many people simply remove wallpaper, apply a thin layer of plaster to the wall (this is known as skim coating) and then re-paint the wall. Often the wall cracks and the surface is compromised within a short time. To help prevent this we recommend that old linings be removed and new plasterboard is used.
There are many good reasons for doing this:
All tools should be clean and free of any old and set plaster. It is recommended that stainless steel tools be purchased if possible as these are less likely to corrode. Remember that these tools are being used to create a smooth finish, any kinks or scratches in the edge of the tool will cause rough areas in the plaster. Do not use broad knives for scraping, opening paint cans, etc.
Paper jointing tape offers superior crack resistance and is the only jointing tape recommended by most plasterboard and joint compound manufacturers. It achieves this because the paper tape absorbs compound, melding with it to form a solid joint. Non absorbent fibrous tapes are unable to do this. Paper tape comes pre-creased and has two distinct sides. The rougher side, facing out on the roll, is always bedded face down into the compound.
Below is a summary of the compounds suitable for use by DIYer’s when jointing plasterboard.
First Coat | Second Coat | Top Coat |
---|---|---|
Gib Plus 4® | Gib Plus 4® | Gib Plus 4® |
Gib Plus 4® | Gib Plus 4® | Gib ProMix® All Purpose or GIB ProMix® Lite |
Gib Tradeset® | Gib Tradeset® | Gib Plus 4® |
Gib Tradeset® | Gib Tradeset® | Gib ProMix® All Purpose or GIB ProMix® Lite |
At external corners, and for holes or gaps deeper than 3mm, the plaster is applied in thicker coats. Because of this, pre-mixed compounds are only recommended for the final coat in these situations. Below is a summary of the compounds suitable for use in these instances.
First Coat | Second Coat | |
---|---|---|
Gib Tradeset® | Gib Tradeset® | Gib Plus 4® |
Gib Tradeset® | Gib Tradeset® | Gib ProMix® All Purpose or GIB ProMix® Lite |
It is recommended that joint compounds from the same manufacturer as the plasterboard be used. In this way you can ensure that the materials are compatible and have been tested as a system.
These are the joins where two edges of plasterboard meet side by side. The plasterboard will have a slight recess (taper) in the edge of the plasterboard, making for easier stopping.
Ensure that all fixings, screws or nails are seated below the surface of the plasterboard. Fill any areas greater than 2mm deep with a setting compound such as Gib Tradeset® and leave to dry. Remove any dust or loose material from the plasterboard. Mixing instructions can be found on the back of the bag or pail.
When jointing sheet ends which are not recessed, care needs to be taken to ensure the surface build up of compound is minimised. The same basic procedure as for tapered edges should be followed, except that each of the stages should be doubled in width, resulting in a 600mm finished joint width.
The same process and compounds should be used as for stopping longitudinal joints.
External corners can be finished with metal trims or Gib® Goldline® profiled plasterboard trims. Gib® Goldline® trims are available in a range of different profiles including rounded corners that are great in high impact areas. Trims are attached over the corner and then covered with compound. Because of the thickness of plaster involved in covering these trims, pre-mixed compounds must not be used for the first two coats. Use the compound selector in Table 2 when selecting compounds for this application.
Skim coating involves covering the entire plasterboard surface with a thin layer of finishing material to give a smooth, consistent texture across both joints and the paper surface of the plasterboard.
If skim coating is the only option for you, or you have a special requirement for a very smooth finish such as in a critical light area, then it is recommended that a tradesman is used. Walls must be prepared in different ways depending on whether it is new plasterboard, has been painted, has had wallpaper or even if the plasterboard is old. A tradesman will be aware of the correct way of preparing the wall to reduce the risk of problems in the future.
The quality of the final decoration is dependent on the quality of the jointing. Using Table 4, inspect the quality of the jointing prior to decoration. TIP: Imperfections will be easier to see by shining a light, such as a torch, along the wall. This will show up any imperfections as shadows.
What | How | Remedy |
---|---|---|
Overfilled (Crowned) Joints | Look for excessive shadowing | Sand back |
Underfilled (Starved) Joints | Look for excessive shadowing | Fill with a pre- mixed compound and finish as per Edge (Longitudinal) Joints - Top Coat |
Over Sanding of Joints | Look for scuffed paper and scratch marks | Repair with a pre-mixed compound and lightly sand |
Tool Marks | Look for ridges, gauges and holes in the joint area | Repair with a pre-mixed compound and lightly sand |
There is plenty of information available on painting plasterboard, however, the following guidelines give a summary of best practises.
Use flat paints rather than semi-gloss or gloss where possible. Gloss paints will reflect light to varying degrees, exaggerating surface imperfections.
Light colours tend to diffuse light helping to disguise any surface imperfections. If it is intended that dark colours will be used then it is recommended that the services of an experienced tradesman be sought.
Avoid the use of harsh lighting such as wall washers or creating situations that give harsh light, such as windows extending to a wall or ceiling line. Where ‘harsh’ or ‘critical’ lighting conditions occur, i.e. where the dominant light sourceshines across the surface, imperfections will be easily seen. Consider skim coating the wall or applying a wallboard prep coat. Use water-based paints, except in wet areas, as these will make it easy to create an ‘orange peel’ effect which helps to disguise any imperfections.
‘Cut in’ around edges and doors with a paint brush and then apply the remainder of the paint system using a medium to long nap roller (7-20mm). This will aid in creating a soft ‘orange peel’ effect. Always maintain a ‘wet edge’ with the roller and apply the last coat with the roller marks in the same directions and parallel to the dominant light source.
Paint systems should always be applied in accordance with the manufacturer instructions.
It is important that an oil-based sealer is applied to the surface prior to wallpapering. Some wallpapers are quite thin and the joint may “telegraph through” due to differences in porosity between the joint and the plasterboard surface. Applying a sealer also aids in the removal of the wallpaper at a later date if redecoration is required.
NOTE: Whilst the advice and recommendations contained in this brochure have been produced with proper care, they are offered only with the object of assisting those interested in or involved with the jointing of plasterboard. Winstone Wallboards Ltd and BRANZ do not accept responsibility for the advice, recommendations, etc., contained herein.