GLAZING

BY CHAKAMBA J.

This presentation consists the following: Definition of glazing By laws governing ventilation requirements By laws governing daylight admittance Tools and materials Types of glass and uses Preparation and procedure (steel windows

only)

Introduction

DEFINITION

Glazing is the process of fitting glass part of the window to the frame which is essential to let in daylight and exclude rain and elements of weather (Walton 1995).

Glazing is the act or process of fixing glass into a frame or surround in domestic work. This is usually achieved by locating or placing the glass in a rebate and securing it with putty or beading in accordance with the recommendations contained in BS 6262: Glazing for buildings (Chudley and Greeno, 2005).

 The fitting of glass into openings in doors and windows

(Fleming, 2004).

Definition continuedThe working definition for glazing is that it is

the process of fitting glass panes into door and window frames using putty or beads.

Model Building By-Laws 1977 state the minimum ventilation requirements for a habitable room as being 5% of the floor area of the room.

This means that the area for all the openings in room that are capable of being open for ventilation purposes should amount to 5% of floor area of that particular room.

These include windows which can be opened, air vents, permavents and or service openings

BY-LAWS ON VENTILATION

Circular No 6 of 1991 of the MPC&NH (Ministry of Public Works and National Housing in Zimbabwe) recommends that for all windows used on residential construction, 50% of the area of the window should be capable of being open to the external air for the ventilation of the room.

While glazing can be done, some windows may have some glazing panel that is slightly smaller than the rebate into which they are fixed to allow for the fitting of a permavent.

The area of the ventilation openings can be calculated as; 5% x Area of the Floor=area of ventilation

BY-LAWS ON VENTILATION -Continued

BY-LAWS ON DAYLIGHT ADMITTANCE:

Daylight admittance tableThe Model Building By-

Laws specify the daylight areas in accordance with the following;

Type of Habitable Room

Minimum daylight area as% of floor area

Any Habitable room

10%

kitchen 12%

Workshop 15%

Daylight bye laws -continuedThe glazing used on the windows should be

clear enough to permit daylight or natural light into the building.

Barry specifies that such material should be transparent or translucent so as to promote daylight admittance.

Calculation of the Daylight Admittance is also done on the formula;

Area of Windows ÷ Area of the Floor x 100%

MATERIALS USED FOR GLAZING

For a steel sash window frame, these normally include;

Glazing PanelsGlazing PuttyTurpentine and Paint.

Glazing panels-types of glass

Types of glass-continuedDrawn Sheet Glass/Clear Glass: This type of glass is normally 3.13mm or 4mm thick

and is used for general purpose work on a building.Obscured Glass:A type of glass that has patterns rolled on its surface

although obscured plain is also available. Thickness range from 3.13mm to 6.25mm depending on where they should be used. It is used where aesthetics is of the glass architectural work is important such as on churches, halls and auditoriums where a minimum amount of daylight shall be permitted as a design.

They can also be used on bathrooms

Glass types-continuedTempered Glass is glass that is reheated and rapidly cooled, which causes it to break into pea-sized pellets.

GLASS TYPES-CONTINUEDWired Glass: Used where fire resistance is required such as

in factories, kitchens and other places where fire is always used,

contains some thin mesh reinforcement wires in them.

They are normally available in thicknesses ranging from 4.69mm to 9.37mm depending on where they are needed.

 

WIRED GLASS

GLASS TYPES-CONTINUED

Toughened/Armored Glass This type of glass is normally used for

Aluminum sliding doors, French doors and Wooden and Glass Paneled doors on public places.

Thickness includes dimensions from 4.69mm to 9.37mm depending on where they shall be used.

Glass types-Heat absorbing or rejecting glassTinted blue glass Tinted grey glass

Is tinted to absorb a high degree of solar radiation and thus it transmits less solar heat and glare into building.

transmits most of the visible daylight required in a building

It is usually bronze, grey or blue green in color

Heat-absorbing glass

MATERIALS OF GLAZING-TYPES OF GLASS- CONTINUED

Opaque Coloured Glass: A type of glass that is normally used for

interior and shop decorations. The thickness is usually more than 4mm (Ezeji 1989).

There are various other types of glass whose list is exhaustive

GLASS TYPES-LAMINATED GLASS is made by sandwiching a transparent

polyvinyl butyric (PVB) interlayer between sheets of glass bonding the three layers together under heat and pressure.

When laminated glass breaks, the plastic sheet holds the broken glass in place, thus reducing the risk of injury in case of breakage

LAMINATED GLASS

Glazing Materials continued- PuttyTypes of putty Linseed Oil PuttyThis is traditional putty which contains a

mixture of linseed oil and inorganic fillers (BS 544: 1969). It sets by a combination of aerial oxidation of the oil and some absorption into the timber.

A hardening skin is initially, produced but the mass ultimately sets to a semi-rigid material later on. The putty hardens faster in cold seasons than in hot.

Linseed putty-continuedApplication is done with a putty knife onto

primed timber or frame rebate. For application to steel window frames, non absorbent hardwoods and water-repellent preservative treated softwoods, non-linseed oil putty is the most appropriate sealant compound.

Linseed oil putty should be painted within two weeks, whereas metal casement putty may be left for three months before painting (Lyons 2007).

Types of putty- continued Metal Casement Putty: A compound sealant suitable mostly for

glazing on steel casement window frames. It is made from refined vegetable drying oils

and finely ground chalk. It takes time about three months to harden

but just like the linseed oil putty, the hardening process is faster in cold seasons than in hot seasons.

TURPENTINE:  A solvent that thins and makes the putty workable. PAINTS:  Paints consist of a blend of components, each with their

specific function. Commonly these include the binder (or medium), solvent, base, extenders, pigments and driers, although other additives may be incorporated into specialist paints to improve their properties (Lyons 2007).

 

Glazing materials-continued

  When the putty is hardened to a certain degree, it may

need to be painted. From the various types of paints that can be used in building construction, gloss enamel paints are recommended for painting both the steel window frames and their putty.

While the steel frames normally have their body painted with a red metal alky or red metal oxide priming coat on manufacture, the metal casement putty will need to be painted with all the three coats of gloss enamel paint namely the priming coat, the undercoat and the finishing coat of the required colour.

Glazing materials-paints

TOOLS FOR GLAZING

Glass Cutter:  A handy tool consisting of a handle with some

teeth and a cutting wheel. It is used for cutting glass to the required size (Fig 1). The teeth are used for breaking the glass in strips as it is cut.

Glass cutter

Fig 1: The Glass Cutter and Putty Knife.Source: Mugari and Pekoyo (2008; 91)

Glazing tools

Cutting procedure

Mark on the glass the required size. Place the pane on a flat surface and make a

groove along the line marked. Use the teeth on the glass cutter for

breaking

Tools of glazing-continued

Tee square Putty knifeA tee shaped tool

consisting of a long straight edge and a stock. It is used for describing a straight line with a glass cutter during the process of cutting a glass. A metal tee square or straight-edge is more preferred than a plastic or wooden straight-edge.

Another handy tool consisting of a steel blade and a handle. It is used for compacting and cutting putty when fixing it to a slope. See Fig 1.

PRE-GLAZING PREPARATION

Estimate your usage of putty for the glazing job but do not prepare more than you can use in 40 minutes.

Set sufficient putty aside for the backing putty (no drying compound added).

Place any unused putty back in the liner and fold to seal. Shake the drying compound well before use. Split the putty required into four segments. Add an

equal portion of drying compound to each quarter. Sufficient drying compound is provided for the whole bag of putty.

Pre-glazing preparation continuedReplace the cap on the unused portion of

drying agent. Mix each quarter and then the four segments

together to ensure that the drying compound is mixed into the putty.

Knead the putty and drying compound for ten minutes.

For optimum performance ensure that unused putty (with drying compound added) is not kept for more than 40 minutes.

PREPARATION AND PROCEDURE FOR GLAZING

Clean the steel frame rebate to receive the glass pane to remove dust oils and grit.

The cleaning process should be done with a damp rag dipped in turpentine or paraffin.

 Take a ball of putty and knead until soft until soft and pliable.

PROCEDURE OF GLAZING-CONTINUED

Press the glass pane firmly and lightly into the frame rebate while cutting off excess putty from the inside. Take care not to break the glass as you fit it into the rebate.

The glass may be secured by springs or clips if required.

Apply front putty on the outside edge of the glazing pane recently fit onto the rebate using

 a putty knife

Apply some back putty around the rebate of the frame. This will act as a shock absorber when the glass is fit and when the window is closed with a bang.

Ensure that the glass pane to be fit is 2mm or 3mm smaller than the rebate right round to allow easy fixing.

GLAZING PROCEDURE-CONTINUED Press the glass pane firmly and lightly

into the frame rebate while cutting off excess putty from the inside. Take care not to break the glass as you fit it into the rebate as shown below

GLAZING PROCEDURE CONTINUED Apply second layer of putty around the

glass as shown by the diagram below

GLAZING PROCEDURE-CONTINUED Hold the putty at an angle of about 60

degrees and cut excess putty as shown below.

Smooth the putty using putty knife as shown by the diagram below

IMPORTANT GUIDELINES

Ensure that the frames (new and existing) are free from dust, rust, oil and dirt. Old putty should also be removed. Metal frames should be painted with a primer (allow the primer to dry for at least 16 hours). Wooden frames must be sealed with a suitable wood sealer.

Backing putty (the putty applied to the frame behind the glass) should be 3mm to 4mm thick. Do not add drying compound to the backing putty, as you need to allow for applying the putty by hand using your thumb. This will ensure sufficient adhesion to the frame.

Upon placing the glass pane, apply a firm pressure at the edges of the pane. Do not press in the centre of the pane.

The holding putty (the putty applied to secure the glass in place) must be finished off with a putty knife. A 60 degree angle is standard.

GUIDELINES-CONTINUED Application is done with a putty knife onto

primed timber or frame rebate. For application to steel window frames, non absorbent hardwoods and water-repellent preservative treated softwoods, non-linseed oil putty is the most appropriate sealant compound.

Linseed oil putty should be painted within two weeks, whereas metal casement putty may be left for three months before painting (Lyons 2007).

THIS WHOLE PROCESS OF FIXING THE GLAZING PANE IS ILLUSTRATED IN THE DIAGRAM BELOW

Post glazing procedures As stated by Lyons (2007), allow the metal

casement putty at least three months to harden without tampering with it or pressing it with your to feel its state of hardening.

Paint the putty as required in three days time applying the priming coat on day one, the undercoat on day two and the finishing coat of the required colour on day three.

Post glazing procedures-continued As you paint, take care not to smudge or to

mess up the glazing pane with the paint brushes. Thin brushes should be used in a firm and controlled movement of the hand. Apply a universal undercoat to the frame and putty.

As specified apply the final layers of the paint 

ConclusionThis presentation was about glazing which is

done in buildings to improve its aesthetic value.

The need for skilled glazier is highly called for, to produce good workmanship and quality work.

REFERENCES:

Barry R. (1999) The Construction of Buildings, Volume 2 Fifth Edition, Blackwell Publishing (Pvt) Ltd, Oxford.

Choga, F.,V. Mukova& B. Mushowo(2006) Focus on ‘O’ level Building Studies. Harare: College Press

Chudley R. and Greeno R. (2006) Building Construction Handbook, Third Edition, Heinemann Butterworths Publishing, Oxford.

Ezeji S. C. O. A. (1989) Building Construction, Longman, London. Fleming E. (2005) Construction Technology, Blackwell Publishing (Pvt)

Ltd, Oxford. 

Fleming E. (2005) Construction Technology, Blackwell Publishing (Pvt) Ltd, Oxford.

  Lyons A. (2007) Materials for Architects and Builders,

Third Edition, Elsevier Heinemann Butterworths Publishing, Oxford

MPC&NH (1997) New Minimum Revised Standards on Low Cost Housing Designs, Ministry of Public Construction and National Housing, Harare.

  Mugari K. and Pekoyo I. (2007) O-Level Building Today,

Zimbabwe Publishing House (Pvt) Ltd, Harare. 

Reference continued

Lyons A. (2007) Materials for Architects and Builders, Third Edition, Elsevier Heinemann Butterworths Publishing, Oxford.

 Mugari K. and Pekoyo I. (2008) ZJC Building Today, Zimbabwe Publishing House (Pvt) Ltd, Harare.

   Walton D. (1995) Building Construction: Principles

and Practices, Macmillan Education Ltd, London.   Zimbabwe Government, Model Building By-Laws

1977, Government Printers, Harare

Reference continued