This started as a small area of rot in one of the corners. But once I started It became apparent that the whole cill had perished.
The exterior walls had been rendered and the interior walls plastered after the window had been fitted. It would have meant either a re- rendered exterior wall or a re-plastered interior wall if any attempt was made to remove the window frame, so replacement was not an option.
The property which is a grade 2 is situated 100meters from the beach. All new work was finished in a marine primer and marine grade paint will be used.

An area of wet rot to a 1930s window appears to be the result of either water ingress past the putty or insufficient primer used when painting a previous repair. As you can see I  made  a cut out of the effected area leaving in the piece that has the interior moulding it may have been a whole new window if the wet rot had eaten away at the moulding.

A new piece was then added and fastened with glue and screws, timber plugs were used to plug the screw holes. Not entirely necessary but a far more professional finish. Once dry the window was re-hung and primed.

There is pressure to replace wooden windows with PVC-u this has come about partly by plastic window industry which has heavily invested in marketing, with the often optimistic claim made to fit replacements  in one day to a whole property, and the promise of a seamless experience with out the need too bring in other trades, may seem an attractive one.

The term ‘worn out’ is often used by the salesman to describe the condition of original windows rather than an actual assessment being made and the whole idea of replacement is driven by a culture of fashion  and upgrades. This can result in inappropriate adaptations particularly in a conservation area as PVC-u cannot match the

Sections and proportions of historic joinery. Historic joinery would be represented in most  pre 1970s dwellings.

Windows are the eyes of a building and profoundly effect its appearance and in addition represent the artistic social and economic development of an area and also reflected in many cases the status of a dwelling and its occupants.

Due to the high quality of timber used in the original, old windows can have long lives, often I come across windows that are 100,150 or even 200 years old and are usually economically repairable. It would take many years if ever that you would get back savings on heating having PVC-u fitted, and energy offsets making PVC-u windows in the first place are enormous. Estate agents often refer to the fact that replacement of historic windows and doors to PVC-u threaten the value of your property particularly in conversation areas.

Broad Glass.

A method used widely in the 12 and 13^th century found mainly in churches and cathedrals made by blowing a bubble of molten glass swung to create a tube this was then laid and flattened with  the ends cut. Once cool the tube was cut into small rectangular lengths of sheet glass.

Crown glass.

Molten glass was spun producing a disc examples exist from the 14^th and 15^th century but when the tax on glass by weight ended cylinder glass became popular. Crown glass was made up to the 20^th century.

Cylinder glass.

A type of Broad glass but with advanced methods employed it became possible to make larger tubes, this method became popular up to the beginning of the 20^th century and many examples exist in private dwellings of that period.

Polished plate glass.

Developed in France glass was laid on a polish table and ground and polished to produce a clear sheet as mechanisation was being introduced glass for the first time was becoming less expensive this method was employed between the 18^th and 19^th century.

Drawn glass.

Often referred to as flat sheet. Molten glass was drawn between a die a bit like the old fashioned mangle used to wring clothes producing a flat continuous sheet.

This became the industry standard many examples still exist. It can be identified by the mottled effect and bubbles unless your property was bomb damaged during the war years or through some other breakage  you probably have this type.  

Float.

Invented in 1950 molten glass is allowed to flow over molten tin it results in a completely flat and featureless product of exact thickness and characteristics throughout.  

Development in glass production from around the 16^th century  was reflected in the appearance of windows. Pieces of broad glass were laid in lead quarries but buildings still had often only one window that opened whilst servant quarters and low status rooms were not glazed, a waxed cloth was used along with shutters to keep the night out.

It was not until the 17^th century that casement windows with sliding sashes became fashionable and with the onset of larger sheets of glass it became possible to fit these into rebates within the frame and glazing bars with metal sprigs were employed to keep the glass in place and finished in putty to keep the weather out.

The earliest sliding sashes had the top sash fixed. The lower one slid upwards and was held in place with pegs.

Not commonly known is that  the double hung sash window that you see today was a British invention although the French like to think it was theirs! As they were the ones who came up with the bottom sliding sash.  Using counter weights both sashes could be opened enabling a system of ventilation to be employed. The earliest example dates from 1701 and by 1750 most new development employed this system.

Many variations of this theme were employed and being British ridden by class the better off had swept heads (curved) , bowed, and elaborate decorative glazing bars. This can often be seen in fan lights above main entrance doors which also were becoming popular and stamped on the world a message of status.

Both Crown and cylinder glass was used during this period.

Glazing bars also were going through a development from large chunky Oak members to slender ovolo and quarter circle mouldings this in part was due to the import for the first time of cheaper softwood mainly Scandinavian pine. By the 19^th century glazing bars were down to 12mm wide with pointed gothic mouldings.

With the introduction of cheaper plate glass from about 1830 which was stronger and available in larger pieces the need for glazing bars was reduced allowing for larger areas of uninterrupted views to the outside.

Energy efficiency for reasons of economy, comfort and, reducing carbon emissions are a major priority. Economy because we all want to save money and there is only one direction that fuel bills go. Comfort – who would want to live in a cold home with draughts which adds not only to the economy argument but also the emission part of the trilogy.

Carbon emissions in my view is the big one, an extra jumper or thicker curtains will mitigate to a certain extent the issue of comfort but carbon emissions affects us all.

The amount of energy required to manufacture PVC-u windows and doors will take many years before it is off set buy savings in reduced emissions achieved by installing them if ever and there is to my knowledge no recycling of these units which are now becoming a landfill problem.

A whole building approach by that I mean looking at all possible ‘heat sinks’ can help in reducing waste.

The heat loss from windows can vary considerably it depends on the size of the window in ratio to the external wall. Heat can be lost through poor installation and ill-fitting sashes, conduction through the glass and from radiation through surfaces.

Retro fitting draughts excluders and brush seals outlined else where on this site can dramatically reduce draughts, bear in mind draughts can move in two directions into the room and out of the room.  Research has shown that fitting these simple seals can have an 80% impact reduction. Another benefit also is the acoustic proofing that results from these seals.

On the subject of research, thick curtains the sort my mother used to hang at the beginning of every winter- they were made from a second hand stage curtain which once hung at the old Atherly Cinema in Shirley can have the same thermal impact as double glazing. Not that we all have second hand stage curtains but you hopefully get the message.

Incidentally double glazing multi-paned windows will not give you the same thermal efficiency as secondary glazing either as there will be thermal bridging through the numerous glazing beads and frame.

So in conclusion without the need for double glazing to be employed  a combination of the correct seals- that is compression seals for windows that close against the frame and wiper seals for parts that move against each other, sliding sashes come to mind. The closing of any gaps around the exterior of the frame. Curtains or blinds and secondary glazing will keep you warm and snug without compromising the aesthetics.

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The cords had broken on these shutters, and I could not locate the pockets to access the weights in order to re-cord them. I had to refer to a publication by George Ellis titled ‘Modern Practical Joinery’, printed in 1902, for the answer. As you can see, the pockets had been cleverly hidden behind the panel which I found surprising as I could just at a push get my arm into the cavity. Perhaps in those days arms were not so big, or this kind of work was undertaken by an apprentice with slender arms.

What I didn’t want to do was to take off the front panel to access these pockets; it’s been fixed in place since the 1850s. The windows are the original, fitted in 1796, but the balance shutters are a later addition. This was established by the presence of the original skirting board inside the shutter case. Also, the building was once owned by the Church and had a reliable record of works carried out over the last  two centuries.

Sometimes the pocket sits near the top of the frame, about 18” down from the pully wheels, which I now understand became the practice during the early part of the 20^th Century.

Whilst doing this work it occurred to me what a fantastic way to eliminate drafts, light and noise. Those late Georgian / early Victorian designers really did think of everything, and the skill employed by the carpenters and joiners, with limited rudimentary  machinery, I can only admire and take my hat off to.

I am hoping that one day I will get an enquiry asking how can I eliminate drafts, light and noise with box sash windows fitted, as I would relish the opportunity to manufacture and fit a 21^stcentury copy of such a practical solution to an age old problem.

There are modern day solutions that can be employed to reduce considerably the draft and noise problem associated with box sash windows, and these are covered in previous work and articles on this web site. I am happy to undertake such work but the elegance of balance or lifting shutters cannot be matched.

This particular porch is in good condition apart from the corner post and cill. The rotten timber was cut out and a hard wood replacement offered up and glued in place, Merranti was used for the post and the cill, the original being an inferior pine, that however was not the cause of this rot, a leaking gutter above on the corner was to blame.

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This particularly fine example of a double bow window manufactured and installed in the early 1950s was made by Crittal, who have been trading since 1849 originally in Braintree Essex. The steel windows are almost as good as the day they were made a testament to their quality, the cills were also surprisingly in a reasonable condition although each meeting joint had to be scarfed. The customer who was very pleased with the results was originally quoted over £25,000 for replacement! I came in at a fraction of that price,  There was absolutely no good reason to have these replaced, all they required was a’ birthday’ which will see them through for another 60yrs

An annual visual check and action on potential weak spots, coupled with a 5-7 year cycle of re-painting, will be sufficient to protect your timber windows for many years. The oldest windows I worked on were installed in the 1700s. They were ‘tired’ but because they had been included in a maintenance programme over the centuries (the windows were part of a church estate), they were in remarkably good condition.

Moisture readings:

As a matter of course I measure the moisture content of your windows, starting at the cill and moving up every 6” until I get a reading of between 12 and 18 percent. This will give me the information I need to asses the extent of potential wet rot areas. On average no more than 10% of any given window will be rotten, including the cill.  Repair rather than replacement will be economically viable in all but the most exceptional cases of damaged of frames and openers.  Of all the windows in a year that I assess, I see perhaps five percent that are beyond economical repair. In these few cases, it is cheaper for me to manufacture and fit like-for-like wooden replacements.

What is wet rot?

Essentially, it’s a fungal attack on timber that has high moisture content for an extended period of time. There are two main types: white and brown, with several less common types also in existence.  You can easily identify both white wet rot and brown wet rot. The former has the appearance of fine threads and often a soft white tissue structure. This type is usually found between openers and cills or transoms. Brown rot appears as cracked cube structures, often brown and brittle, found on exposed timber and joints. Of the two, white rot is probably more destructive as sometimes the fine hairs can travel onto masonry.

Treatment is the same for both: cut it out and replace the affected area with new timber. If the spores from white rot have penetrated the brick this will need to be treated with an appropriate chemical solution.

Window glossary: Here you can see the common terms used when describing windows.

Putty
The number one cause of rot, it cracks over time, usually starting in the corners, water gets in, and the damage starts.  Water sits in the rebate where it has no means of drying out sufficiently, until next winter arrives, bringing more rain and, for good measure, a frost, which freezes the water between the glass and putty. This then expands, letting in more water, and the cycle repeats.  These events will set in motion wet rot behind the putty in the rebate. If the damage is in the corner of the window, the joints between the bottom rail and stiles, mullions, and glazing bars start to suffer as well. It would be wise to check the putty on your windows once a year; it only takes five minutes, and if it is showing signs of degrading then get it raked out and a fresh bead put back in. You can tell if new putty is needed by seeing if there are any cracks in the putty or if it has come away from the glass, in which case you often see moss or dirt between the glass and putty.

Other causes of wet rot in openers can be as described above for window frames: poor quality paints, problems regarding the throat, shrubs, and leaking gutters.

Below highlighted in red are the most common areas vulnerable to wet rot.

There are very few instances where a window frame has become damaged by rot any significant distance above the cill.  Such rare instances have four main causes: when water gets into the drip bar or the transom; when a closed opener sits tight on the transom leading to capillary action; when the opener loses the throating, usually the result of swelling, so someone shaves off the bottom rail so that the opener fits again and doesn’t put in a new throat; or finally when the throat has become filled with layers of paint over the years. There is a reason why the throating should be present all around the opener: it is to stop capillary action taking place.

The most common area where you will see rot is in the corners of the cill and in the first 6” on the frame jamb.  It can be caused by the above mentioned faults, or by the pooling of water in the corners coupled with a poor paint surface.  If the paint cracks at this crucial joint and water seeps in, the water has no where to go and no means of drying out, perfect conditions to allow wet rot to take hold.

Other causes of wet rot can be: poor quality paints allowing moisture penetration; painting timber with a high moisture content; timber of inferior quality (usually not applicable to pre 1970s frames); shrubs growing too close or against the timber; and gutters that leak.

The culprit. A leaking gutter over time will do this damage.

Repairs to a bay window the result of a leaking gutter. Showing the damage to the frame and cill and a example of one of the pieces taken out and finally the repair

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Replacement of rotten cills to a former Victorian school, the grooves in the brickwork were made by pupils in the 1800s that used the bricks as a sharpening stone for their pencils, a marine primer was used to protect the new cills until a painter can finish in the desired gloss.