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
Goods in transit are liable to move about a little. It’s entirely natural and impossible to prevent, be it movement in the factory, on a delivery vehicle or the fitters installing the window.
Not surprisingly then, sometimes balance springs can slip off the "shoe", designed to hold the balance and sash together. Detached balances generally mean a service call is required, which we seek to avoid.
That’s why the balances on every Masterframe sash window are held firmly in place with a retaining clip, that once snapped into position locks the balance in place for life.
You will never need a service engineer and we won’t have a service call to make.
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 31 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 II)
The Vintage Collection comes standard with Torso II spring balances tested to 50,000 cycles
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.
When measured for a Post Office Counters project they exceeded the specified test of 50,000 opening cycles – they switched off the machine at 180,000 cycles…
The Torso may be expensive but it remains the ultimate spring balance and can be made to suit any length or weight of sash.
The Vintage Collection comes standard with a Masterframe locking cam catch in a range of colour options.
Each collection has a range of cam catches 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.
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.
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 come with continuous horns as standard with the option to not have horns at all.
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.
The Vintage Collection comes with a deep 105mm bottom rail as standard.
The exclusive deep GRP cill is available as standard on the the Vintage Collection sash window is a beautiful feature designed to achieve the authentic appearance of an original 3” timber, useful for use in a Conservation Area.
The deep 56 mm cill is indistinguishable from the other PVC-U sections because all are bond wrapped in the same Renolit foil to maintain the appearance of timber.
The deep cill is 16.8 times stronger that a regular cill and this strength allows larger and unusual windows to be replicated more authentically, for instance where required in sea front hotels, renovated / converted former schools, industrial buildings and ecclesiastical buildings.
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.
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.
Integral slim mullion
The visible mullion between windows in some cases can be as wide as 250mm, which is nothing like the slim mullions on original timber windows. On triple window styles, where the centre sash slides and the two wings are fixed, thick sight-lines are even more obvious, negatively impacting on any authentic detailing.
The bespoke slim mullion measures just 99mm across the front face, which substantially reduces the overall thickness of the sight-lines. Double or triple sash windows no longer look bulky and will complement the period aesthetics of your home.
The slim integal mullion is avialable on the Vintage Collection.
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 welded construction
The Vintage Collection can have mitred, diagonal welded jonts as an optional feature.
Ovolo And Chamfered Sashes
We know you’ll care about authentic details as much as we do. Externally old wooden sash windows had putty glazing, which sloped back to the glass at an angle of 45 degrees, however many trade windows have an artificial, sculptured or Ovolo leading edge.
While Ovolo sashes are the perfect match for casement or door profiles with the same feature, traditionalists will favour the Chamfered putty line sashes.
All our sash profiles are all multi-chambered. This means there are three individual pockets inside the sections so that the galvanised steel reinforcement is inserted into its own sealed chamber, well away from the separate drainage channel that allows rainwater to run away easily.
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.
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
All trade ranges 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.
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.
This name is a registered Trade Mark that describes a unique patented method of construction that produces traditional timber style butt joints both on the inside and the outside of the window. The Vintage Collection comes standard with Timberweld® technology.
Timberweld® technology in summary: -
- The all-important advantage of a product that incorporates Timberweld® technology is that it is beautiful and authentic, looking every bit like a timber original and giving the impression that it has been lovingly produced by a master craftsman.
- Most butt joints in the market today are open ended however, your Timberweld® joints are completely sealed from the elements with no open chambers to allow in rain water, draughts, bugs and flies!
- Aesthetically, Timberweld® joints will blend in with all architectural styles, Georgian, and Victorian, and will be suitable for use in both conservation areas and in the most contemporary developments. The technology is material neutral and in the case of PVC-U, Masterframe sash windows will be the perfect match for casement windows and doors that are offered with Timberweld®.
As a result of this innovation, Masterframe is the ONLY PVC-U sash window manufacturer that can promise you an authentic, wood effect joint, complete with perfectly sealed frames and corners that look just like the timber originals.
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.
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.
Limit stops are available colour suited to all other furniture in a variety of colours and are always fitted in pairs to prevent the lower sash distorting.
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
A Wood foiled finish replicates the painted grained effect of timber and is standard in white on the Vintage Collection.
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.
Colour matching is available to any Farrow & Ball, RAL, British Standard Colours and other leading paint manufacturers' colours.