Astragal Glazing Bars
Done well they transform a window, however all too often companies fail to appreciate or inform their clients about the impact that internal canes will have on their installation.
Normal “double glazing” companies often provide the cheapest method to mimic glazing patterns, regardless of how real they look.
Cheap to produce, but flat, dull and extremely poor imitations of the real thing, they remain brilliant white and out of character against the weathered feel of the rest of the window.
We will happily make sash windows with plant on bars, to whatever design pattern you require. We use Georgi® clips to clamp the two bars (external and internal) onto the glass, we then interlock the bars where they cross over to ensure they never become detatched. The adhesive backing tape is just there to stop the bars rattling in the wind. The BBA have tested our method of bars and clips and confirmed that they expect them to stay attached for the life of the sealed unit.
Balance Retaining Clips
Exclusive balance retaining clips lock balances in place for life! Masterframe only use top quality Torso and Ultralift pre-tensioned balances. Even so, there is a possibility that if relying only on the fit of the linkage into the shoe, these could become detached during transport or installation. That is why the balances on every Masterframe sash window are held in place with an exclusive balance retaining clip, that once snapped into position secures the balance, preventing it from becoming detached.
Balance retaining clips are another small enhancement we incorporate to give you extra peace of mind when moving our windows and saving your customer from the inconvenience of a service visit.
Sash windows are generally comprised of two sliding sashes, each retaining a double-glazed, sealed unit. In most cases, the window will be "split" equally in the height so the visible glass will be the same height in each unit, although in Scotland, 1/3and 2/3 splits or 40/60 splits are commonplace.
However it’s important to have clean lines that run vertically through the upper and lower sashes, so that the plant on bars align and to ensure the Georgian squares will be of equal size.
Look closely at neighbouring houses and you’ll soon see the mishmash of glazing panes, because cheap mock sash or imitation sash windows tried to mimic these important fenestration details but failed.
On original sash windows, the sash was nothing more than a sliding pane, pegged open to stop it falling.
Later, ropes and then chains were used to make lifting the sash easier, as the weight of the glass was counterbalanced by lead or cast iron weights. This meant wooden windows were very easy to open, as they hung freely in the rebate (when not painted shut) and remained static when opened because the lead and glass were counterbalanced.
Today we use the same principal of counterbalancing the weight of the sash, but glass is at least three times heavier and there is insufficient room for three times more lead.
Sash window manufacturers make five basic types of balances to choose from. These vary in budget and effort required to raise or lower the sash:
Clock springs or constant force balances
Block and tackle or cord and pulley balances
Wind up balances (Alumatilt)
Pretensioned Spirals (Ultralift)
Pretensioned double sprung balances (Torso)
We don’t make spring balances; we have used Caldwell Hardware as our supplier since we started making sash windows 25 years ago. This is because they make each type of balance mentioned above, but refuse to import some to the UK because they consider them to be inadequate for the UK market.
Some UK companies ignore Caldwell’s advice and import balances direct from the States. This means you may get offered windows with balances that are unlikely to perform as you may expect. Should you need detailed information, visit www.caldwell.co.uk
An overview of balances
These are larger versions of clock springs, like a metal tape measure on its side, which unfolds when the window is operated. Used extensively in America for secondary glazing or ultra-lightweight double hung windows, when tested to the American Manufactures Association tests (AMA) they are not expected to exceed more than 3,000 opening cycles. They are extremely cheap but Caldwell, who manufacture them, refuse to import clock springs into the UK. They’re simply not sturdy or strong enough for the windows found on the UK market and give no assistance when opening a sash. Masterframe never use clock springs.
Block and Tackle
Again, extensively used in the US for small, lightweight windows. They consist of a nylon cord approximately 2mm in diameter, wrapped several times around a pulley system and housed within a three sided channel. These balances are also very cheap to import but not expected to exceed 3,000 cycles. Caldwell make them for the American market and don’t import them to the UK for the same reasons – they provide no assistance when opening a sash. Masterframe never use block and tackle balances.
Wind-up balances (Alumatilt)
These are a lightweight balance for small windows or infrequently used windows. A continuous tube encases a twisted metal rod, known as a spiral. Although reasonably sturdy and competitively priced, they need to be “wound up” to the desired tension.
They remain twisted throughout the expected 5,000 opening cycles, however they are known to relax, meaning the upper sash will drop of its own accord, requiring adjustment.
This twisted state means that for its entire life, the balance looks to unwind if mishandled. A two-year warranty is average for this product that is highly likely to require some adjustment at some point in its life, however they do offer some assistance towards lifting sashes. Masterframe only ever offer wind ups if specified by clients.
Pre-tensioned spirals (Ultralift)
This is a smooth operating balance, with the tension set in the factory or pre-tensioned. A spiral rod held against a spring encased within a plastic tube makes Ultralift an excellent balance. They are designed for sash weights up to 28/30kgs. They have been independently tested at the BBA to exceed 20,000 opening cycles (that’s over 25 years if opened twice a day). They offer reasonable assistance towards lifting sashes. Masterframe use Ultra lift balances on all trade windows and Bygone Melody as standard.
Double sprung (Torso)
Designed by a Dutchman in 1946, they epitomise great engineering. Individually manufactured in 0.5kg increments (1lb) and tailored for perfect lengths, these balances have two springs; one wound clockwise, the other wound anti-clockwise
As a sash is opened, one spring extends, getting longer, and the other compresses, getting shorter, so they are counterbalanced for their entire life. This means they are immensely reliable and in general offer 30% extra assistance when lifting the sash.
The Torso may be expensive but it remains the ultimate spring balance and can be made to suit any length or weight of sash. Masterframe use Torso balances as standard on the Vintage range.
Each collection has a range of cam catches, from simple CC1s on our Heritage range, to CC4s on the Classic or Authentic products. Vintage has the new and exclusive claw cam catch in a range of colours and each range can have “enhanced security” although this comes standard on the Vintage range. This enhanced security is essentially better locks, to ensure compliance to the Police preferred standard known as Secured by Design.
Our Bygone collection has its own bespoke claw cams. They are SBD as standard and handed left and right as matching pairs to provide additional security, with a choice of Acorn or Beehive designs and three luxury colours. We also have a traditional Porcelain ball design.
Water has a knack of finding any weakness. Sash window joints are no exception; that’s why we invented adhesive foam pads that seal the joints between the cill and the window frame.
Although protected locations may not need these pads, we set high standards, so every window we produce, regardless of range, has these bespoke cill pads as standard. That way neither you nor we ever need to worry about water ingress.
By investing a little extra during the manufacturing process, you’ll be protected from the inconvenience and disappointment of damp walls or wet carpets.
Deep Bottom Rail
Traditionally, the lower rail of the bottom sash was made from 4" or 5" timbers, planned to about 100mm. This was substantially heavier (deeper) than the side members or mid-rail because it had to carry more weight than the upper sash.
While it is far quicker, less expensive and easier to weld profiles of equal size, welded and grooved corners do not look traditional, so deep bottom rails on all our product ranges are mechanically joined as standard.
In order to retain equal sight lines or occasionally to reduce costs of an opening window, it is possible to make dummy sashes.
These are real sashes made in the same fashion as sliding ones; only the window furniture, hardware and balances are removed. Not all windows need to open. Providing you have sufficient opening area for the floor area of the room (normally 1/20 is recommended) there is no limit to the number of sashes required to open.
Obviously we recommend the top and bottom sashes open on the same window, so that you benefit from the rapid purge ventilation when it’s needed, but providing you are happy with the ventilation of the room, we will manufacture as requested.
External Sash Horns
Victorians produced larger, thicker and heavier sheets of glass so they incorporated sash horns to the underside of the top sash. These acted as a “stop”, to prevent sashes being over-extended, smashing the pulley wheels or damaging the lead weights inside the box framework.
Today, sash horns are purely decorative as there are other methods to prevent sash windows being over-extended; however they are often retained to keep the traditional appearance of box sash windows.
All trade ranges have the option of decorative, “clip on” horns or sculptured from the sash itself, as “run through” or “continuous horns”. While clip on horns are considerably easier to make and therefore far cheaper to produce, the effect of continuous horns is far superior.
Sash windows need expert fitting; they don’t work very well if poorly installed. Unlike casement windows, there isn’t any coverage or overlap; air tightness comes from compression on the brush pile.
While there is no substitute for accurate fitting, we provide all sash windows with foam baffles – pads specially produced to reduce air infiltration.
Most people push, pull, or lift their sash windows using the Georgian bars not the handles, just watch yourself next time…
Whilst Astragal bars add character and charm to the window and recreate the original look, using them as handles excerpts considerable pressure on them, pulling them off in your hand. Getting the correct bond between glass and bar is critical.
Companies who lack experience will tend to stick bars onto the glass individually, but this increases the opportunity for shoddy joints and the number of bars that could fail. Besides which, most companies specifically exclude plant on Georgian bars from their guarantees.
Masterframe windows are unique. Clever, patented interlocking joints where the bars meet, together with Georgi®-clips (patented to our company), mean that each bar is continuous and cuts the full size of the sash. Each bar is secretly notched so they are inter-locked, clamped and then bonded against the glass surface.
We are so confident with this technology that you can open and close any of our sashes using the bars; they won’t come off.
Lift-Out Pivot Bars
Carrying 40/50kgs for the next 20 plus years it is important that the connection between sashes and balance mechanism is robust. Rather than cheap plastic components or short metal bars, we provide windows with split bar technology, meaning you can remove the sash without touching the balances.
Solid, durable and very strong these will easily work for the life of the window.
Mitered, Cut And Welded Construction
Mitered, welded joints have been with us since PVC-U was first used. 45 degree saw cuts enable welding joints that are quick to make and easy to fabricate but a diagonal line isn’t traditional on wooden sash windows.
While many are happy to install grooved joints, some installers ask for polished joints. These can be done, however we do not recommend polishing PVC-U because you must start the polishing process by scouring the extruded gloss surface, which is impossible to get back. Dirt tends to gather on the polished joints and soon looks grubby.
Ovolo Beading Internally
Trade windows all have the same bead, Ovolo in shape. It’s designed for 4.16.4 (or similar 24mm) sealed units to be fitted, to look just like an original timber window.
However, because Krypton and Argon gases work better in thinner sealed units, we use a thicker, more traditional bead and internal Georgian bar on our Bygone Harmony and Bygone Symphony collections. In addition to making the sealed units (and window) more energy efficient, the deeper bar also enhances the traditional appearance and creates a platform to allow Brighton catches to be fitted.
All Masterframe sash windows can be tilted inwards to make cleaning easier and safer. Particularly large sashes cannot be allowed to tilt for cleaning, as the sash is simply too heavy, exceeding the maximum permissible weight to be tilted safely.
Lighter sashes can be heavy but those exceeding the maximum sizes could be dangerous. That’s why uniquely, on every Masterframe window that exceeds the safe size for the standard easy clean, tilt restrictors, we fit a short pair of safety stays.
So if a large window should be accidentally opened, it will remain vertical, unable to damage anyone or anything.
We are the only manufacturer to fit safety stays to oversized sashes.
Although they do not allow for cleaning, they WILL stay upright and prevent accidents.
Scroll Handles And Pole Eye
Our Heritage range has an integral handle bead while Classic, Authentic and Vintage have scroll handles. These are always supplied loose, as some clients prefer to leave them off; others have very specific ideas for where they should be fitted. They come in a blister pack with its own clever template for hole positions.
It is customary to have a “ring pull” or “pole eye” fitted to the centre of the top rail on the upper sash (a swan neck hook and pole can be supplied if required). Alternatively, a “D-Handle” can be supplied for fitting to the underside of the top sash if requested.
Extrusion companies who design window profiles recommend that sashes are fully reinforced with galvanised steel, to provide adequate resistance against burglars.
This reinforcement is also needed to prevent profiles deflecting in windy weather and to strengthen the sashes so they are capable of carrying the weight of the glass. This also provides a strong, secure fixing for the handles, latches and other components.
Not every company complies with the manufacturing rules the extrusion designers lay down. Some manufacturers reduce costs by removing this reinforcement altogether. Others insert recycled plastic reinforcement sections, again to cut costs. We understand the importance of steel reinforcement. Although it drags down energy performance (which we regain using clever glass) you can be assured our windows are secure.
While we will produce straight, slide sash windows if asked, most clients request we make tilt and slide sash windows.
Short spring-loaded "bolts" engage the sash behind the frame section. While standard ones are mainly plastic, and often fiddly or cumbersome to operate, ours are smooth and easy to use.
While Heritage have a basic finger latch, all Classic, Authentic and Vintage windows have our unique, “sashsecure”™ finger latches. These are steel reinforced and wrap around two sides of the sash to centralise sashes within the frame, strengthening the security of our windows.
All tilting windows either have tilt restrictors or safety stays.
Tilt restrictors are metal side arms, made from stainless steel, that prevent windows from being dropped accidentally when being tilted inwards for cleaning.
Naturally we want to ensure that you never have a problem so we always fit a pair of tilt restrictors to each tilting sash. On exceptionally large windows, too large to be tilted for cleaning, we fit “safety stays”. These are short side arms, that ensure windows cannot be accidentally dropped, keeping everyone safe.
Most manufacturers of tilt restrictors have arms made from sheared metal. These leave an extremely sharp edge which acts as a pair of scissors, cutting through the brush pile and reducing its effectiveness every time they are opened or closed, causing draughts.
All Masterframe sash windows have stays with especially rolled edges, rounded to ensure the tilt restrictor slides past the brush pile, leaving it to do its job – preventing drafts.
Travel Stops Or Limit Stops
These fittings prevent a window from opening beyond 100mm (until they are manually overridden) and are particularly useful for upstairs bathrooms and bedrooms.
Although plastic limit stops (LS1s) are available, most people prefer the solid feel of aluminum versions (LS5s). Available in a variety of colours, they are always fitted in pairs to prevent the lower sash distorting.
There are alternative solutions to these limit stops when the window is required to only ever open to a set dimension. Extended cover strip at the sides act as length stops to prevent windows being opened beyond the desired position, in place of these travel restrictors.
If specified we can provide trickle vents for your windows. While new build insists upon some form of background ventilation, replacement sash windows don’t need trickle vents unless the original windows had them.
Airborne dirt and road noise will be noticeable whichever vent is used; we strongly suggest you consider two stage keeps as an alternative solution.
There is nothing much to worry about with our windows – it’s just the sashes we make can be very heavy and we’d like to remind you and your client of this before you try tilting them when cleaning.
They have been tested not to fail but these sashes are heavy.
Window Furniture – Colour Coordinated
When considering bargain prices, do ask yourself why. Companies who offer cheapest prices generally buy components based upon price too, and you end up with handles, cams, keeps and release knobs in three or four different colours of brass, on the same window.
Caldwell hardware have provided Masterframe with colour matching furniture since we started, so we avoid this issue.
Wood Grain Finishes
While shiny white plastic is sometimes requested to meet budgets, most clients favour wood grained or wood foiled sash windows because it replicates the painted grained effect of timber.
Normally white wood grained foil is specified however Cream, Tudor black frames with white sashes and timber finishes like Light Oak are very popular. Bending is still possible with foiled profiles however painted finishes are best done after bending.
For the perfect looking sash window that requires little maintenance and no repainting, why not select any RAL colour on a foiled window.