Measuring:

Units should be measured to allow approximately 1mm clearance all round where the rebate depth is 7mm. Allowance should be made where the opening is not perfectly rectangular. Where the rebate depth is in excess of 7mm, additional clearance can be allowed, but always ensuring that the sight line of the perimeter seal is below the sight line of the back rebate.

Glazing Timber Fore putty

All rebates should be clean and clear of minor obstructions and brushed cleaned and primed. The rebate should be bedded with a non hardening compound (butyl) to provide a bed between the back rebate and glass of approximately 2mm. The unit should be placed into bedded opening and pressed equally around the perimeter until the 2mm back bed is obtained.

However whilst the back bedding should be a non hardening compound such as butyl commonly used, silicon is sometimes used but mainly on metal windows.

 The unit should be held in position by sprigs, which are thin metal shaped diamonds which are fixed into the rebate with a sprigging gun.

The use of a sprigging gun ensures that the diamond sprig is less than 1mm from glass, and prevents any scratches to glass surface. The sprig should be set at 150mm centres or as necessary for small panes.

The fore putty should be carried out with Linseed Oil Putty or Steel Sash Putty, as BS6262 to the rebate depth sight line or just below to allow for paint finish line on putty. Putty should not be painted for at least seven days. The minimum fore putty on rebate width should not be less than 6mm. The function of fore putty is to protect the frame by shedding the water from the frame.

It is important that the fore putty should be brushed with a fine duster brush to ensure that there is a good seal on the putty against the glass.

Glazing Timber Beads

All rebates should be clean and clear of obstructions, brushed clean and primed. The rebate should be bedded with non hardening compound (Butyl) to provide a bed of approximately 2mm between the glass and back rebate. The unit should be placed against the bedded back rebate. The unit should be placed against the bedded back rebate and pressed equally around the perimeter until the 2mm back bed is obtained and only trimmed flush when glazing has been completed.

The rebate width should then be bedded with non hardening compound to obtain a very thin bedding not exceeding 2mm or gun grade which has a much thinner consistency. The timber bead which should be angled to provide a water shed and should be bedded against the glass by applying the compound to the front edge of the bead in sufficient quantity to prevent voids when fitted against the glass and excess trimmed, matching the water shed angle of the bead.

The finished height of the bead should be 2mm below the back rebate height to allow the painter to paint over the trimmed water shed angle of the compound to match the angled bead. The paint finish is important to provide protection against the rain and sun and the compound should be allowed to cure for at least 7 days before painting.

Note

Where timber beads are to be pinned into the rebate width is particularly narrow the beads should be pre-drilled with a very fine drill.

Metal Windows

Glazing Slimlite Double Glazed Units to existing metal windows, after removing single glazing, and primed with metal primer. The existing single glazing was held in place by metal clips fitted into metal holes in the rebate. As the holes are not re-usable, the best method of glazing is to bed the back rebate or rebate height with approximately a 2mm bed of silicone and the unit pressed back against the silicone which when cured in approximately a day or two will hold the glass permanently in place. The rebate width can now be foreputted with a steel sash putty to finish approximately 2mm below sight line to allow painting to finish to sight line. It is important that the fore putty should be brushed with a fine duster brush to ensure there is a good seal on the putty against the glass.

Note

Sprigs, Sprigging Guns and Duster Brushes

Can be obtained from any company selling miscellaneous glazing tools.