Rods and Mortar

A. Reasons To Use	E. General Data Sheets
B. Golden Rules	F. Fitting Instructions
C. Accessories	G. Curved Walls
D. Calculating Opening Sizes

A - Reasons To Use Rods & Mortar System

Internal and external panels

Straight or curved walls

Rods and Mortar forms the basis of fire rated construction

Click here to return to contents

B - Golden Rules of glass block installation using Rods & Mortar

1) Glass block walls are self supporting, but not load bearing.
This external stair tower was constructed using steel box sections. The whole structure was infilled with glass block panels that could expand and contract freely. The steel box section supports the roof independently and no downward pressure is placed on the glass blocks.

2) For best integral strength, glass blocks should be installed into a four sided pre-prepared opening. This opening can be timber, brick, steel, concrete or blockwork.

2a) The vertical box section creates the jambs of the opening.

2b) The horizontal beams provide a head and cill for the glass block panels to be anchored to.

3. Glass blocks expand and contract with temperature change. Glass blocks should not be installed when the surrounding temperature is 5°C and falling or 30°C and rising.

4. Openings must be square and perpendicular and designed to suit glass block modules. Glass blocks cannot be cut like masonry bricks or tiles. Click here for more information on calculating opening sizes.

5) Maximum panel size without intermediate slip joint is 25m2 with no single dimension exceeding 6m in any direction.

6) Accessories for Rods and Mortar construction:

Spacer Pegs
10mm spacer pegs are available to assist with accuracy of construction and prvent mortar squeeze.

Glass Block Technology also has a 6mm horizontal and vertical spacer peg in the product range, this can be used only in conjunction with 80mm thick glass blocks. It is primarily used in conjunction with smaler glass blocks for example - 115x115x80, 190x190x80 or for curved glass block screens where it is subject to a tighter than recommended radius.

When the spacer peg is fitted and the wall is finished, the tabs at the end twist off and this is then grouted over.

When detailing opening sizes, the minimum opening can be calculated using this simple formula:
The dimension of the block + the width of the joint x the number of glass blocks + one more joint = minimum opening size.

These working formulae will vary if you are using U channels, different size blocks or different size joints or the panel is curved. For assistance contact Glass Block Technology.

Joint Sizes
When constructing glass block walls using 190x190x80 or larger dimension glass blocks, Glass Block Technology recommend the use of 10mm horizontal and vertical joints.

Perimeter Expansion Joints
Expansion and contraction is one of the most critical aspects of any glass block construction. Expansion joints must be incorporated to the perimeter of all glass block panels (as detailed on GBT data sheets).

For the head and jambs of any specification a 10mm thick foam should be used. It is extremely important not to bridge this expansion joint in mortar, it should be caulked over using silicone.
If the joint is bridged, it may cause blocks to crack (see Diagram 1 above left).

Cills should be prepared by using either a bitumen strip or two coats of bitumen emulsion, to allow for compression caused by the weight of the panel yet ensuring that the base course of glass block mortar does not adhere to the substrate.

When the height or width of the panel exceeds 6m, either a vertical or horizontal support should be incorporated, or a horizontal or vertical slip joint. (See data sheets GBT 0009 and GBT/0010).

For curved glass block walls, expansion joints must be inserted around the perimeter and where the curve changes plane. (See datasheets GBT 0017).

Reinforcement
Stainless steel ribbed reinforcement rods are used to anchor glass block panels in place and increase integral strength. The rods should be at least 5.5mm diameter and a minimum of one stainless steel rod should be used within each horizontal and vertical course.

Where reinforcement rods are joined, allow a minimum overlap of 150mm and loosely tie using tie wire.

Reinforcement rods should be anchored into all substratas to a minimum depth of 25mm. An oversized hole should be drilled, then filled with silicon to allow the reinforcement bars to move with expansion and contraction.
For reinforcement with U channels refer to data sheet GBT-0003.

Reinforcement rods should never rest on or be in direct contact with any of the glass blocks. Spacer pegs have a cross section where the rods can be positioned onto.

Reinforcement Rods in construction (left) - Spacer pegs and reinforcement rods (right)

Panel Anchors

As an alternative to drilling oversized holes, panel anchors can be used especially when constructing into steel sided frames. Isolation pads are required to separate the stainless steel panel anchor from steel surround.

Using U Channels
U channels are often used to assist in applications where an opening has to meet a specific dimension.

It can also be considered if
an opening has been prepared incorrectly and the dimension is too large. The figure can
be reduced by incorporating
an individually fabricated
U channel.

It is crucial that the U channel is lined correctly with expansion fibre and when the channel is filled with glass block mortar at least two number stainless steel ribbed bars are inserted.

Glass Block Mortar
Glass Block Technology recommend the use of Colmef Vetromix glass block mortar when constructing brick by brick. Colmef Vetromix is used as a bedding mortar and then by slightly diluting the mix it can be used as a grout for finishing.

Suitability
Colmef Vetromix can be used internally or externally for straight and curved glass
block panels

Mixing instructions for Colmef Vetromix can be found on the reverse of each bag.
Colmef Vetromix requires mixing with clean water only to make it workable,
the powder already contains hydraulic binders, inert and synthetic resins.

When constructing glass block walls with Colmef Vetromix always ensure that the surrounding temperature is not 5°C and falling or 30°C and rising.

Technical characteristics of Colmef Vetromix glass block mortar
Figures stated were taken at 23°C at 50% RH and in lack of ventilation

STEP 1

Calculate the correct opening size. Make sure the opening is square and perpendicular. Lay bitumen expansion material along base of 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 out of masonry, brick, stud wall, steelwork.

STEP 2

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 between 25 – 35mm. Fill holes with silicon and fit vertical bars in place (fig.2). 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.

STEP 3

Mix Colmef Vetromix glass block mortar following instructions on reverse of bag (fig.3). The mix should be a semi dry consistency (Slump 1 or less). Lay down a bed of mortar.

STEP 4

Fit first block and tamp 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. (fig.4) 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 at shape.

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 to much, dependent 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.

STEP 5

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. (fig.5).

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, not forgetting to put silicon in the holes, and then cover over the rod with remainder of mortar (fig.6). 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.

STEP 6

Fit next row, checking vertical and horizontal alignment.

STEP 7 - FINISHING THE GLASS BLOCK PANEL

When the wall has set, snap off spacer tabs and grout all joints with diluted Colmef mortar.

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.

CAUTION: Restriction can result in block cracking.

Initial Clean and After Care Maintenance
Do not clean with any acidic products, the best product for cleaning is water. Polish each block with a soft cloth using good old elbow grease .Note : Clean face of block as work proceeds.The glass block installer should have left the glass block wall in a clean, unblemished condition. Requiring only periodical cleaning to maintain an excellent appearance. However, there may be a residue of cement on the glass surface left from mortar/tiling grout identified by whiteish bloom when dry. This may be removed by use of proprietary cement stain remover. (BAL HD Tar Cleaner)

Click here to return to contents

G - Rods and Mortar - Curved Glass Block Walls

Curved glass block walls can only be constructed using Rods & Mortar installation system.

The principle of a curved panel follows the same guidelines as straight glass block walls, except the front vertical joint is opened to form a curve.

Expansion Joints
Perimeter expansion should be allowed for around all four sides of the panel, ensure this joint is weatherproofed by caulking with silicon and not grouted over with mortar.

1. Denotes the positioning of the bitumen expansion fibre at the base of the panels.

2. Denotes the positioning of the expansion fibre at the head and jambs of the glass block curved panel.

Slip Joint
Where a curve changes plane, a vertical slip joint must be inserted.

The mortar joint is replaced by the same bitumen expansion foam that
is used at the cill of a panel. The reinforcement rods can be carried through the expansion foam by piercing a hole in the foam and the joint should be caulked with a white silicone, this will visually look similar a standard mortar joint.

Note : Ensure the slip joint is not grouted over in glass block mortar, as by bridging the expansion joint will not allow the panel to expand or contract effectively and may
cause blocks to crack.

Openings
Curved panels should ideally be fixed into four sides : floor/cill, ceiling/head, vertical walls/jambs or an end post.

If the curved wall is secured at the base and only one jamb, an end post should be used as a vertical restraint. (Diagram 1). If the panel can also be fixed at the top, secured into the ceiling, this will offer greater support.

If end glass blocks are used at one end of a curved panel, the reinforcement rods within the panel should be drilled into the top, base and one jamb. (Diagram 2). Introducing double rods will increase the integral strength.

Joint Sizes and Minimum Radii
When constructing curved glass block panels, Glass Block Technology recommend the use of a 10mm internal vertical joint. Using 190x190x80mm glass blocks, the minimum internal radius of 1650mm will result in the external vertical joint being 18-19mm.
For other block sizes see GBT-0017 data sheet.

An example of curved screen in Weck 190x90 half blocks:
Radius = 900mm
Internal vertical joint = 10mm
External vertical joint = 18-19mm
Horizontal joint = 10mm

Click here to download the curved walls Datasheet

Typical example of curved glass block wall - reinforcement
Two pictures below illustrate a curved glass block wall used in a restaurant to divide the main kitchen area from the seating area. The panel was open at the top and not tied into the ceiling. Each horizontal course was double rodded
to assist with strengthening the restraint of the panel and each vertical course was tied into the base.
1. Denotes position of where double rods are drilled into the side jambs at at depths of 25mm minimum.
2. Denotes position of where vertical reinforcement rods are tied into the base at depths of 25mm minimum.
Note : Alternative to drilling holes - use panel anchors.

Click here to return to contents