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First things first: calculate the wall opening
Before anything, you will need to calculate the wall opening for your Rods & Mortar kit. To calculate the wall opening area, take the following steps:
- Take the width of the block (190mm) and mutliply by the number of blocks you need (in this example we use 6 blocks): 190mm x 6 = 1140mm
- Multiply the width of the spacer joint (10mm) by the number of blocks (6), and add it to the above number: 10mm x 6 = 60mm
- Add one more end joint (10mm) to close off the wall.
- The total comes to: (190mm x 6) + (10mm x 6) + 10mm = 1210mm
Note: The Rods & Mortar Kit page will automatically calculate the correct opening size for you based on your selections.
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Step 1. Preparation of opening
Calculate the correct opening size (explained above). Make sure the opening is square and perpendicular. Lay bitumen expansion material along the base opening. Secure expansion foam to jambs and head. All four sides of the opening should now be covered in expansion material. Bitumen is necessary on the base to take the weight of the glass block wall.
Timber frame on images represents a perimeter opening; this can be constructed alternatively our of masonry, brick, stud wall or steelwork.
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Step 2. Continue preparation of opening
Set out dry your first row of glass blocks to ensure opening size is correct. Mark accurately and drill oversized holes in between the blocks, vertically and horizontally where rods will be positioned. The holes need to be a depth of 25mm (min). Fill holes with silicon and fit vertical bars in place. When a horizontal or vertical joint dimension exceeds the length of a stainless steel re bar, overlap two by 150mm & tie loosely using stainless tie wire.
Panel anchors can be used as an alternative to drilling oversized holes and are an ideal alternative to drilling holes if the opening is a metal box section or steel I & H beam etc.
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Step 3. Laying first course
Mix Colmef Vetromix glass block mortar following instructions on reverse of bag. The mix should be a semi dry consistency. Lay down on a bed of mortar.
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Step 4. Continue laying first course
Fit first block and tap down gently, fit second block and repeat. Ensure there is enough mortar between the blocks and the base to create sufficient adhesion, compact the vertical mortar joint using a wooden instrument.
Note: Spacer pegs are not necessarily required between base and first row of blocks. When using spacers at the base or up the side jambs cut the legs of the cross spacer pegs to form the correct shape.
Tips
- It is advised to construct the first course and allow this to initially cure so that on returning to build consecutive courses it becomes easier building a firm bed. In ideal circumstances around 6-8 courses before the panel will wobble too much, dependant on the panel width. Spacer pegs assist with stability, but back shuttering could be considered for additional support. At this point it is advised to stop building and allow the panel to set prior to completing construction.
- For loose build of glass blocks ensure enough time is set aside to fully build.
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Step 5. Building the panel
Repeat Step 4 until you have completed the first row. Insert spacer pegs in between blocks, this prevents steel rods from touching glass, assists with accuracy of vertical & horizontal joints whilst preventing mortar squeeze, enabling more courses to be constructed.
After the first course is complete, if left & allowed to set it will make building subsequent rows easier due to building off a firm bed. Lay half the quantity of mortar and fix the horizontal rod in position, remembering to put silicone in the holes, and then cover over the rod with the remainder of mortar. Rods have to be positioned every row vertically and horizontally.
If using a 'U' channel, two stainless steel reinforcement rods are required around the perimeter.
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Step 6. Continue building the panel
Fit next row, checking vertical and horizontal alignment.
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Step 7. Finishing the Glass Block panel
When the wall has set, snap off spacer tabs and grout all joints with diluted Colmef mortar.
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Step 8. Sealing and weatherproofing the panel
Rake back and mastic around perimeter of expansion foam to create weatherproof seal and prevent bridging which can restrict expansion and contraction of overall panel.
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