Eco-friendly and pocket-friendly frames

Raj Kumar Aggarwal

The frames of doors and windows are generally made from wood as it is easily available and can be prepared in any shape, size with decent appearance. After the ban by the government in 1993 on the use of wood or timber in the construction of buildings to check the ruthless cutting of trees and to save environment, civil engineers recommended Pressed Steel, Cement concrete, Aluminum and PVC for the frames (chowkats) of doors and windows. Since then Pressed Steel Frames are being used successfully in  buildings.

The use of Pressed Steel Sheet frames is recommended in place of wooden chowkats where the threat of termite infestation is high. Pressed steel chowkats look like wooden chowkats and can be used in all types of buildings. All types of wooden shutters old or new, flush shutters of particle board and wire gauge shutters can be used conveniently in these frames.

The pressed steel door and window frames are made by machine pressing the 1.25 mm thick cold rolled low carbon steel (CRC) sheets to give the shape of a frame (chowkats). These chowkats are made with single rebate (pattam) to hold panel shutter only and with double rebate to hold both panel and wire gauge shutters. 151x60x40mm to 165x60x40 mm section is used for double rebate frames, where as 90x60x40mm to 125x60x40mm section is used for single rebate frames. The pressed sheet profiles are welded together to make door and window frames. 

Inside of the frame is coated with anti-corrosive paint to protect it from corrosion and outer surface is painted with metal primer for protection from weathering agencies. Properly painted steel frames provide rust -proof long life.

The steel frames are provided with  necessary accessories like recessed hinges to receive wooden shutter, hinges for chowkats to keep shutters in open position, stops to prevent the shutter from damaging the wall plaster when fully open. The provision for  receiving tower bolts, locking arrangement and fixing door springs are also made on these frames. Temporary ties of MS angle 20x20x1.25 mm are also provided at the bottom to maintain the shape of the door frames. Three holdfasts (lugs) 40mm wide 200mm long are also welded on each side of the frame to keep the frames in position while fixing at site.

These hollow steel frames are filled with ( 1:3:6 ) cement concrete mix before  fixing at site to maintain the shape of the frame  and to provide strength to the chowkats. Rigid Polyurethane Foam having high strength to weight ratio is also used to fill the steel frames. Cement concrete (1:2:4) mix is used for fixing holdfasts during construction.

Pressed steel frames are economical in comparison to all other types of wooden chowkats. These frames are more hygenic and durable. These are free from the effects of warping, twisting, shrinkage and splitting. 

Most pressed steel frames are made as per IS.:4351 specification and are easily available in the market. These can also be customised as per individual or architect's requirements. Single rebate 115x60x35mm size chowkats are available @ Rs 70/per running ft whereas double rebate frames having size 151x60x35mm are available @ Rs 80 per running ft. (The cost of cement concrete and fixing is not included in this rate.) Centre Mullion (Internal member) of doors and windows frame is charged 1.5 times of these rates.

However pressed steel door frames, if not protected properly by paint, are a bit less suitable for bathrooms and toilets, where water contact is unavoidable. 

The Aluminum or Poly Vinyal Chloride (PVC) door frames, which provide total protection against corrosion, moisture and termites can also be used in such  situations. 

Pressed steel frames are very suitable for  areas having termites. 

Substituting pressed steel frames or any other frames in place of wooden frames (chowkats) is a cost effective and eco-friendly option.