Window Installation

Installation of Windows

Windows are largely installed to enable daylight into a room, but it is vitally important that they serve their purpose by keeping in heat and withstanding all weather conditions.


The most common types of windows are:


  • Casement windows
  • Boxed frame windows
  • Bay windows
  • Stormproof


Timber was once the most popular type of material used for windows, however windows are now most commonly made from PVC, aluminium and metal. It is imperative that windows are able to stand the extreme weather conditions that they can be exposed, as well as being secure and hard wearing. They must also be able to keep heat in and should be therefore appropriately insulated.


To ensure a window meets its requirements they are made up of a variety of parts that serve different purposes. The parts used can vary depending on the type of window used however the common types will have:

  • Frame- The main structure of the window that supports the entire window
  • Head- The main horizontal top of the window frame
  • Jambs- The horizontal frames that form the sides of the window
  • Sill- The bottom horizontal piece of the frame
  • Jambliner- A piece that sits on the side of the frame to offer a snug fit for the window sash
  • Mullion- A major structural piece either horizontal or vertical between the head and the sill
  • Top Rail- The upper horizontal piece of a window sash frame
  • Bottom Rail- The bottom horizontal piece of a window sash frame


Main window types

Casement Windows

Casement windows are the most traditional type and have a solid outer frame made of wood. Within it they have smaller frames called casements or sometimes sashes. The frame comprises of a head, two vertical jambs and a sill. The vertical parts are called mullions and the horizontal parts are called transoms. Casement windows usually open outwards and the hinges can be at either side (depending on which side you want them to open).

Casement windows are good for weather proofing. They are specially made to avoid water coming into the home. They are fitted with a groove around the outside edges of the head, jambs and sill which prevents water coming through. The sills are sloped which allows the water to run off.

The main benefits of casement windows are that they are easy to operate and open, which allows for good ventilation in the home. They are usually built in the brickwork and secured with frame cramps.


Box Frame sliding sash windows

The box frame window, sometimes known as the box sash window are not used as often in modern housing. They are mainly used in old or listed buildings. This is because casements windows are seen as much easier to make and maintain.

They are made up of the frame and two sashes. The sashes consist of a top sash which slides down and a bottom sash which slides up.

Usually the sashes operate by using pulleys, which counterbalances the weights attached. The weights have to be balanced to allow the sashes to slide into the correct position. The weights attached to a pulley, move and slide up and down within the frame. Most box frames sliding sash windows now use lead rather than iron weights and have hectical springs rather than the traditional pulley arrangement.

The different components of a box sash window are:

  • Head- The horizontal top part of the frame. The inner and outer linings attach to this.
  • Pulley stiles- The side part of the frame. The pulley siles are a guide for the sliding sashes. They are made from a mould called a sash stile. The inner and outer linings attach to this.
  • Inside Lining- The timber that forms the horizontal board. The staff bead is fixed to the inner edge of the lining.
  • Outside Lining- The timber that forms the vertical board.
  • Back lining- The timber board that attaches to the back of the inside and outside lining and encloses the weights.
  • Sill- The base of the window which the frame is built. It encloses the inside and outside linings and the pulley stiles. It is specially shaped to remove water.
  • Sash weights- Iron or lead weights that counterbalances the sashes.
  • Staff bead-  A piece of timber moulded that keeps the bottom sash in place. It is fixed to the inside lining.
  • Parting bead-  Separates the sliding sashes and secures them in place. Set into the groove in the pulley stiles and the head.
  • Pockets- An opening in the pulley stiles that allows access to sash cord.


Bay Windows

Bay windows protrude out from the front of the house/ building. There are a number of different types which can be built in three different ways. A pre-built bay is the easiest way of constructing a bay window as its built when the walls of the building are and is therefore part of the original design of the building. It forms part of the room inside the house and therefore gives further space to a room. Another way in which a bay can be constructed is called a built bay. This is where the bay is built onto the original design of the building. The wall is usually opened up and construct the bay into it. This will again give further space to the interior room. An alternative option would be to have a window board and leave the existing wall. This is a good way of gaining extra storage. Another method of constructing a bay window would be to have a supported bay. This doesn’t give any extra interior room as no wall is built, but will allow for a bigger window board section. It will therefore be a smaller bay.


Stormproof windows

Stormproof windows are similar to casement windows however they are made to be able to stand much harsher weather conditions. The outer frame is more or less identical to the tradition casement window however the sashes are recessed to cover over the gap between the frame and the sash. This protects the window even further from any water entering the property.



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Oliver Wild Ltd, Unit A4 Alison Business Centre, Sheffield, S2 1AS, Company Number: 7803633, VAT Number: 177-1194-93

0114 2486907 | [email protected]