Thursday 28 August 2008

Technical FAQ's

Q. Can you plaster onto Knauf Aquapanel?
  Yes, with Aquapanel Q4 Finish. This is a specialist finish designed specifically for wet areas over Knauf Aquapanel. You cannot use a normal gypsum plaster. Consult Knauf Technical department for more information if necessary.
Q. Can you stick Knauf Aquapanel to a wall?
  No, Aquapanel must be fixed to a framework - consult Knauf Technical department or the Aquapanel brochure for more information.
Q. Do I need to strengthen the studs around door and window openings?
 

Yes!

The studs need to be stronger to cope with the weight of the door and forces caused by slamming etc. Typically this would involve either boxing the studs or sleeving them with channel, as well as including a timber insert. The Knauf Manual provides standard details for forming door jambs, although suitable timber framing assemblies may be required to adequately support heavier doors. For large openings, or if there is a large area of partition above the opening then a stronger lintel may be required. It is also important to make sure openings are accurately formed to prevent gaps or cracking caused by movement.

Q. Do I need to use Wallboard Primer prior to decoration?
  Unless the plasterboards are going to be finished with a skim coat of plaster, then the answer is yes. Knauf Wallboard Primer should be used over the jointed surface. It seals the board and creates an even texture ready to receive decoration – without it, you may be able to see the board joints. Wallboard Primer also facilitates the future removal of wallpaper without damaging the board’s surface. Two coats of Knauf Wallboard Primer will create an effective vapour check.
Q. Do we always need to seal the perimeter of a partition, even when it is to a flat surface?
 

Yes!

It is essential that Knauf Acoustic Sealant is used to seal the entire partition perimeter to adjoining surfaces if the partition is to provide the specified level of sound reduction - a tiny hole can destroy a partition’s acoustic performance. The sealant should be applied in continuous unbroken beads to the underside of all tracks (and to studs abutting walls). Ensure that all the surfaces being abutted to are clean and free from dust. Any gaps in excess of 6mm should be filled with Knauf Jointing Compound.

Q. Does it really matter if I'm not careful when I fix the plasterboards?
 

Yes!

The correct use of the correct type of fixings is vital to both the strength of the whole partition and to prevent future problems, such as cracking of the joints. Plasterboards should be fixed securely to all supports, using approved Drywall Screws, working from the centre of each board. Screws should be positioned not less than 10mm from the board edge, at 300mm centres - reducing to 200mm centres at external corners. Screw heads should be set in a ‘depression’, and the screw gun torque set so that neither the board paper or core are broken.

Q. How close can the Knauf Wall Liner system be fitted to the background?
  The Knauf Wall Liner system can be fitted down to the depth of the Knauf C-Channel – 17mm. This will however also depend on how flat and true the background is.
Q. How do I repair damage to plasterboards?
  Minor Damage
A. For slight damage to plasterboard, in which the paper surface has been scratched or dented, but there is no damage to the plaster core, the damage to the paper should be rubbed down lightly with fine sandpaper and, where necessary, the area filled with Knauf Joint Filler to bring the surface flush.

Impact Dents
A. In cases where the paper has been deeply dented but not broken through, the board should be inspected for core damage. If there is none, then the procedure above should be followed. In some cases the core itself may have been damaged to the point at which it disintegrates, rather than just dented. In such cases the advice of Knauf Technical Services should be sought.

Wet Boards
A. Plasterboards are not designed to be used in damp or wet areas (with the exception of specialist moisture resistant boards, such as Knauf Moistureshield, which may be used in damp – but not wet – areas) and irreversible damage to the board’s core may occur if the board is allowed to get wet. Also, fungi may grow on damp paper surfaces. Generally, replacement is the best option if boards are allowed to become wet – advice should be sought from Knauf Technical Services.
Q. How many boards can I put up with a single bag of bonding compound?
  A 25kg bag of Knauf Bonding Compound has a coverage of 4.6m² when dot and dabbed. This equates to roughly 1½ boards per bag (8' x 4').
Q. If my setting out isn't perfect, can I make up the difference by increasing the size of the board joints?
 

No!

As a rule, the wider the board joints the more chance there will be of cracking. Tapered edge plasterboards should be lightly butted together when fixing prior to jointing. A 3mm gap between boards should be left where cut or unbound edges occur.

Q. Is any pre-treatment required prior to tiling onto Knauf Aquapanel?
  No, any dust should be wiped off and then Aquapanel can be tiled onto directly.
Q. The partition I want to build is taller than the longest stud you manufacture. How do I get around this?
 

Splicing Studs

If the partition you are building requires longer studs than those manufactured or supplied, then you will need to join two studs together to make one of the correct length. In all cases the following rules apply: The overlap for the join should be 20% of the partition height or 1.2m, whichever is the greater. Two Knauf Wafer Head Screws should be used each side of the joint. The joints should be staggered vertically along the partition to avoid a continuous weak line. The following paragraphs detail how to splice each type of stud:

C-Studs – Knauf C-Studs have one flange longer than the other, allowing them to be “boxed” together.

I-Studs – Two C Studs are used back to back, nesting each side of the web. The largest C-Studs that will fit should be used, arranged so that the entire joint is touching the studs.

CT-Studs – Two C Studs are used back to back, nesting each side of the web of the ‘C’ part of the stud. The largest C-Studs that will fit should be used, arranged so that the entire joint is touching the studs.
Q. What is a resilient bar and how do I use it?
 

Knauf Resilient Bar

Knauf Resilient Bar works by reducing the level of direct sound transmission through a structure. The bar has one flange that is screwed to the supporting framework and a separate, corrugated, flange that receives the plasterboard drylining – thus partially isolating the drylining from the supporting structure. Installation – The resilient bars should be mounted perpendicular to the line of the supporting framework, in parallel rows, at the correct centres given for each application. Where more than one bar is used for a continuous run, the bars should be butted together, directly over a support, and both base flanges screwed to the support. The resilient bars should be fixed at a maximum 600mm centres using Knauf Drywall Screws of the following lengths: Into timber: 36mm Into metal: 25mm The cut ends of boards must be supported on resilient bars. The fixing centres for the boarding are as they would be if resilient bars had not been used for the application.

Q. What is the fire rating of a plasterboard?
  Plasterboards are not in themselves fire rated, although they are designated a Class O material under the Building Regulations 1991. It is the entire system that is tested and rated, but the boards used will have the biggest influence on the result. The ratings vary due to what boards are used, what system is used, and in what application. It is important to refer to Knauf’s literature – or to call Knauf Technical Service – to find the correct system to achieve the fire rating required.
Q. What is the U-Value of a Knauf Thermal insulating plasterboard?
  The U-Value is a measure of the thermal insulation given by the whole structure, and the insulating board required will depend upon the existing structure e.g. airspaces, brickwork etc. By referring to the Knauf Manual or Knauf Technical services a suitable Knauf Thermal Laminate Board can be specified to give the required U-Value.
Q. Which side of Aquapanel should I tile onto?
 

Normally the 'smooth' side.

In most situations, the 'smooth' face of the Aquapanel is the side we would recommend tiling onto. Aquapanel is suitable for supporting tiles up to 50kg/m2.

Q. Which side of the plasterboard should I skim plaster finish?
  The face of plasterboard suitable for skim plastering is the front face ( the face with no printing on, and no paper joins ). When plastering onto Knauf Moistureshield (moisture-resistant plasterboard), a coat of Knauf Betokontakt – a bonding agent – should be applied and allowed to dry prior to skimming.