I´m always smiling about people, considering that the best result for taping around windows is dependent to products of a certain brand. Their logic seems to go the way: "the more expensive- the better".
But the reality is slightly different. The best window tape in the world is useless when it´s applied in the wrong way.
By mentioning the "wrong way", I do not want to bring your attention to techniques, how to physically apply the tapes in the best way. This can be learned easily through online tutorials or training courses (prodomo Ireland will provide qualified air tightness training sessions from October 2020 onwards).
I´d like to use this air tightness blog post to bring your attention to the required preparation work, to ensure the best performance of the selected materials.
Sample of window taping, which could be improved
What to do with the DPC?
Is my window fitted correctly?
Is my blockwork sufficient for the selected window tape?
Do I need to tape the full reveal?
The way the window is taped does not look trustworthy.
You can be sure that the air tightness performance won´t be much better than the visual aspect.
Even in 2020, the most installed windows are fitted with inappropriate fixings. The very popular window strap is going from the frame directly towards the block in the most cases, no matter how wide the joint between the window frame and cavity wall closer is. That leads to a detail as seen on the photo, where the strap extends significantly over the cavity wall closer. This common practice leads to difficulties for further trades - namely window taping and cladding of the reveals with plasterboard. Appropriate window fixings should be adjustable and in line with the cavity wall closer. Also, they should be mechanically fixed with hammer fixings or concrete screws to the block but never with nails.
A detail as seen on the photo will definitely end in an unsuccessful window taping. The blockwork in the reveal needs to be levelled and should be as smooth as possible, to ensure a permanent bonding of the window tape, which leads to a good air tightness. No tape in the world can deal with irregularities on the long term. The window tape will just stick for a short moment, by having it overstretched.
When building a standard cavity wall structure, the complete depth of the reveal needs to be covered with an air tightness layer. Exposed blockwork with access to the cavity will lead to air infiltration due to the porous block structure. I highly recommend the use of air tight paint for backing the air tightness performance. When applied to the full inner leaf prior the window taping, it works even as a primer to increase the bonding performance of the self-adhesive window tape.