Professional spacer blocking
For a window element to work properly in the long term, the glass also has to be installed correctly – and durable products of tested quality must be used between the glass and frame. The Roto Glas-Tec product range offers long-lasting glazing blocks for any application.
Correct spacer blocking ensures that glazing is mounted safely, correctly and stably in the frame. What’s more, it has the important task of enabling ventilation of the rebate area and vapour pressure compensation. High-quality blocks protect the glass edges and edge composite.
No small matter
Incorrect spacer blocking can have serious consequences: cracks in the glass, glass breakage, condensation in window panes and discolouration, delamination, leaking elements or elements with limited functionality annoy customers and jeopardise the good reputation of a window manufacturer. But how can you reliably avoid customer complaints and damage?
Choice of a suitable glazing block variant
Premium suppliers like Roto offer a wide range of glazing blocks for different requirements.
- GL-NM – the basic block
- GL-SV – the block with ventilation channel
- GL-B – the block with brake membrane for vertical block positioning
- GL-IB – the block for triple glazing
- GL-UK – the block for high-quality insulating glass such as bulletproof glass, laminated safety glass, sound insulation and sun protection glass
- GL-UKS – the block for facades and protruding substructures
Choosing the ideal block for the element and the glazing is a good starting point for quality assurance in the fenestration industry. But other factors also need to be considered
Correct dimensioning
The glazing block chosen should always exceed the width of the glass by 2 mm. This ensures that the glass unit rests fully on the glazing block. This achieves even load transfer. The block should be at least 5 mm tall or take up 1/3 of the glass rebate if possible, so as not to impede the vapour pressure compensation or drainage. Blocks are usually 100 mm long.
Correct positioning
The distance between a glazing block and the inside corner of the profile must be at least 100 mm, i.e. the length of a single block. The exact positions of blocks depend on an element’s opening type and are explained in the Roto Glazing Guide. This is available to download on the website. For maximum load-bearing capacity, each block should be inserted all the way into the glass rebate. Positioning the block as far as it will go into the glass rebate ensures that it will not slip or move to a different rebate depth.
Spotlight on the glass rebate
If the glass rebate is not completely level – which is often the case with PVC profiles – we recommend using compensating blocks. This is because the pane should always be level and straight in the rebate. Unevenness and the resultant compressive load can cause the glass to crack or break. There are two possible scenarios: either the glass rebate is level, and the glazing blocks can be inserted directly, or the glass rebate is not level. In this case, a compensating block should be used beneath each block to make the glass rebate level.
Vapour pressure compensation, ventilation and drainage
Functional openings for ventilation and drainage are required throughout the whole window system. This is because potentially damaging moisture formation can only be prevented if moisture can escape to the outside. Moisture can attack the glass rebate and cause timber windows to swell, for example. However, it can also damage the edge composite of the insulating glass pane and get into the space between the panes. The result? The panes fog up from the inside and become clouded.
Correctly positioned glazing blocks make ventilation and drainage more effective because they do not impede water drainage or vapour pressure compensation. If a profile with a smooth glass rebate is used, block variants with a ventilation channel must be selected, such as GL-SV, GL-IB or GL-UK. Roto compensating blocks also help with vapour pressure compensation and drainage.
Contact barrier
Glazing blocks prevent the glass edges and edge composite from coming into contact with the profile to prevent damage to the glass edge. So far, so clear. But a lack of material compatibility between the edge composite of the insulating glass pane and the glazing block can be just as damaging to the glazing. Do you want to find out more? Then we recommend reading this article. Or get in touch with us – Roto Sales would be happy to help, especially if you need to urgently clarify important questions about optimum glazing methods.
So small, yet so important
Glazing blocks quite literally play a supporting role in the fenestration industry. Glazing blocks
- ensure a constant distance between the glass unit and the glass rebate
- therefore, support optimum stress distribution and constant ventilation of the glass rebate
- distribute the weight of the glass unit evenly over the sash and frame so that these reliably support the weight of the glass unit in the long term
- transfer forces to the profile, hardware and building structure
- ensure that glazing works correctly and that windows and doors are convenient to operate
- keep the sash and frame stably in position due to the pressure diagonal created during spacer blocking
- therefore, ensure fault-free functioning in the long term
Only an expert should select a block variant and carry out spacer blocking. Technical Guideline No. 3 “Packing of Glazing Units” issued by the Glazier Trades must be complied with. Roto would be happy to help you with any questions which may crop up regarding your window system.