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Window Sills

Window sills are not just decorative – nor are they simply supports for window boxes!

They contribute an important weather-proofing function to the building. They should be designed to shed rainwater away from the wall. This prevents it penetrating into the wall beneath the window frame. However, to do this, the sills must be well sealed into the wall. The window frame should also be well sealed around the edges.

Stone Sills

Traditionally in stone built and Victorian era housing, stone was used for the sills. In Bristol this was normally oolitic limestone on front elevations, “Bath stone”. Sometimes other types of stone were used, such as in Kingswood were Basalt type stone is seen. These sills lasted well when regularly painted with a lime wash or breathable paint to act as a sacrificial barrier.  Now however we often see them painted with non-breathable masonry paints. This traps moisture in the stone causing them to delaminate, which is very sad sight to see, these elements seem often forget even in the grander properties that we survey.

Concrete Sills

We have seen many dampness issues where the window sills have been rendered over or around and this has caused damp to penetrate through the walls beneath. Defects in sills can allow dampness to creep in as in this case – watch our video.

The underside of this concrete sill has a throated capillary drip like a groove cut into the underside of the sill to help prevent water running back under the sill and into the walls below the window sill;

In buildings constructed in the 1930’s and 1950’s metal reinforced concrete became popular. Due to the composition of the concrete, a chemical change occurs over time; the embedded metal will then rust. This causes the sills to be blown apart, as can be seen below. This is not uncommon hence we look for any straight-line cracks on concrete windows sills, which indicates the condition of the metal reinforcements.  The best method of repair is to cut out and replace such damaged sills.

UPVC Sills and Cladding

UPVC windows normally include the option of a light weight extruded UPVC sill which finishes the window in a matching colour.  Cladding can also be used – but in the case below in Highbridge near Burnham, the UPVC has been clad over a decayed timber sill. This is clearly not ideal! The timber should have been cut out and a new extruded UPVC sill installed, which would have been fairly easy as the timber is so rotten…

Windows and Doors

domestic surveys

Windows and Doors

Windows form a large part of a building and give much of its character! They let in light but they are vulnerable to breakage, accidentally or deliberately. They can usually be opened for fresh air but  can be a security risk. Hence they need to be lockable with a key, to be “approved” by insurance companies. They can also allow heat to escape from the building.

On a viewing, you can easily see whether window locks are present . Again, doors need to be provided with locks that are approved to a BS standard.

Window Frames

The simplest test to tell whether  new frames are required?  Open and close the windows in every room whilst you are viewing. This will take minutes to perform but will indicate the likelihood of a bill for replacement – from £400 per window depending on the size. Yes, even on newer builds – as one minute into this video of our surveys in Bradley Stoke shows! https://youtu.be/1FENY2nJ24Y

There are many shapes and sizes of window, in a variety of materials. Genuine Georgian windows had small panes because glass was difficult to make. The Victorians found new methods of firing glass and so large panes, often in sash windows, became fashionable.

Wooden Frames

Into the 1960s, window frames were made of wood.Older timber frames do offer good thermal performance and can give a long service life, assuming careful maintenance has been carried out. However, they are prone to decay. Sometimes decay is visible as rotting wood. Sometimes fillers have been used. Don’t be afraid of gently prodding, to test the timbers. The filler often looks smoother than the surrounding timber.

Metal Frames

In the 1960’s, steel window frames were sometimes installed, often known as Crittall after the manufacturer. These are normally single glazed with very thin frames. Use a magnet to tell if the frames are steel.  These frames perform very badly thermally and normally have a good coating of mould to show that. These should be replaced.

Aluminium frames were used in the 1980’s. These are lightweight and do not rust. They may have a small brown-coloured layer sandwiched in their construction.  This acts as a thermal break to prevent condensation. If this is not present, replacement is certainly necessary.

As this older double glazing was a lot thinner,  replacement is normally required anyway as it is not feasible to upgrade the glass.

UPVC Frames

The early forms of UPVC were often single chamber or extruded solid plastic,hence  older UPVC windows often do not perform well thermally. Newer UPVC windows have multiple extruded chambers. These act as thermal pockets to make sure that they insulate the interior from the outside world. Combined with e-coatings, this gives one of the best performing arrangements available for the cost.The viable life of UPVC window frames is generally reckoned as 25 years.

Since 2002, new window installations should be “self-certified” by FENSA or CERTAS or in some instances Building Control will sign them off.

Ask the vendor or agent when the windows were last replaced.  Are there any guarantees? If 2003 or later, ask if the relevant certifying  documentation is present.

Glass

Single glazing is simply a single pane of glass.If this is the case, it usually indicates considerable age of a window installation. They allow a large amount of heat to leave the building and sums for replacing them should be budgeted. The reduction in heating bills should eventually pay for this alone!  Large panes of glass can also be dangerous if unmarked.

Depending on the age of the installation, double glazing may be e-coated and toughened.  We use some very special laser equipment to determine if this is the case,as can be seen on this link https://youtu.be/3fsDmGnaJjY . You will not be able to do this yourself, so look for the basics. Is there moisture (often looking like raindrops) in between the double glazed panes? If so, the seal to the double glazing has blown. These can seldom be repaired effectively and replacement is then required. This seal failure can often be as a result of pressure from the masonry, so look around these areas for cracks or distortion of the walls.

Doors

Again, doors may be timber, metal or UPVC, with or without glazed panes. The frames can warp, the locks can be ineffective. The hinges can sag. Replacement UPVC doors can cost upwards of £500, much more for French doors or bi-fold doors.  So do make sure you check them by opening and closing them.

While antique glass in doors, particularly entrances and hallways, is very attractive, it can be a safety hazard. It is unlikely to be toughened so is easily damaged by impact. If you have small children, do bear this in mind!