Window Boards after plaster
In some scenarios, fitting the window boards during the second fix stage can be more beneficial to the overall finish of the job. Standard timber or MDF window boards are typically installed as a first fix process, before the walls are dry-lined and plastered, with the plaster finish coming down encapsulate the board. For primed MDF window boards, this operation is practical and acceptable in terms of finish. In scenarios where higher end window boards are being installed, it can be safer to install them during the second fix stage once the plastering has been completed. This minimises the risk of damage caused by moisture, as well as decreasing the total amount of time that other trades spend in proximity to them. This follows the general premise of waiting until as late as possible within a job to install fine finished components, in an attempt to spare them from harm. In terms of the schedule and material deliveries, we may also not have the window boards on site at this point, with them arriving with the other finished components such as stairs and mouldings. By talking to the plasterers, we can end up with window openings that are dry-lined and plastered on all 4 sides, leaving us with a smooth and clean finish at the correct height for the window board to be cut neatly into.
What are the criteria for the installation of window boards after plaster?
Once finished, the visual criteria for window boards installed before and after plaster remain unchanged. The same overhang and horn length are to be created, though the layout differs slightly. Whereas the standard window board is cut oversized, with the thickness of dry-lining accounted for, the finished window boards must be cut to the exact profile of the opening, with perfect tolerances around the window reveals. The finished window boards are likely to be caulked in, but the tolerances are still relatively tight, in comparison to a standard window board.
How are window boards installed during the second fix?
Installing window boards after the plastering has been completed is an easy process, and with a little care can result in a clean and tidy finish. The process for both hardwood, plastic, and MDF window boards installed after plaster is as follows. The first step is to ensure that the surface of the plaster level to a comfortable tolerance of around 3mm. Packing underneath the window board may be required if the plastered reveal is not level/flat, though this might result in the front edge of the board possibly being caulked. As such, this process needs to be carried on from a decent plastering job. We also need to begin with an appropriate width of window board in relation to the depth of the reveal.
To measure and cut the board, a measurement must be taken between the two outside corners of the reveals. A very small tolerance of 1mm should be allowed here to ensure the board will slide into place unobstructed. The length of the horns then need to be determined, with 2” being common in most scenarios. From the end of the board, the 2” horn can be marked, then the measured distance between the reveals, then another 2” for the horn on the other end of the window board. Faint square lines can be made across the whole width of board to mark where both of the horns are. In and ideal world, all of the reveals would be perfectly square to the window frame, though this is rarely the case.
A measurement of the depth of the the two reveals must be then taken from the corner of the wall to the face of the window. A very small tolerance of 1mm should be allowed here to ensure the horns do not prevent the back edge of the window board from meeting the frame of the window. These two measurements are unlikely to be exactly the same. These two measurements can be marked on the board, measured from the back edge of the board in line with the square reveal lines. The remaining distance of the overhang can be extended from each reveal line towards the end of the board to mark the depth of the horns.
The final step involved taking an exact angle from each side of the reveal off of the window frame. Using a suitable length bevel, the body of the tool is registered against the window frame, with the bevel angle kissing the face of the reveal. By registering the body of the bevel off of the back edge of the board, the tool can be slid until the bevel angle touches the inner corner of the horn layout. his angle should be marked and cut. The process should be repeated for the other reveal, once again the angle is unlikely to be the same on both sides. After cutting out the waste and shaping the horns, if we were accurate enough, the board should fit snugly into place with no gaps along any edge. This operation is relatively delicate, as there is not much room for error. That being said, the layout and cutting is not difficult, and these basic skills are necessary for installing finished components.
Once the board is cut, it can be fixed to the plaster sill using some form of construction adhesives, to avoid putting nail or screw holes in the finished piece.