Preparing your property prior to works commencing.
The purpose of this information sheet is to give you a full description of what to expect in your property when engaging us for any of these services. This section also covers draughtproofing expectations, ventilation in your sash windows, painting and future maintenance of your sash and case windows.
Please familiarize yourself with this prior to works commencing and this will ensure a smoother transition whilst works are ongoing.
Follow this link for guarantees, terms and conditions and payment terms, should you choose to contract K Construction (Scotland) Ltd – Edinburgh Sash and Case for your joinery works.
Our main works can be broken into the four categories which are listed below.
- Single Glazed Refurbishment
- Installation of new sashes into existing casements.
- Full new sash and casement installation.
- Painting works.
Single Glazed Refurbishment Works;
These works involve fully refurbishing your casements and would be considered to be your first level in maintenance works. You can expect the windows to be working well, and all rotten timbers to have been replaced. The pointing will normally be replaced externally. The casements and sashes will have had sanding and fitting work carried out to them to bring them up to a much higher standard, but the sashes and casements are obviously original and unlikely to be perfectly square and plumb, and therefore have a lesser level of draught-proofing. The moulding detail will probably not be as sharp as with new sashes as the previous build up of the layers of paint loses much of the detail. We would expect a level of around 70% draught-proofed.
Installation Of New Sashes into Existing Casements;
The second level for works to your sash windows. If you are considering upgrading your existing single glazed sashes to double glazed sashes or if your sashes are rotten, our workshops will manufacture new sashes to be installed in your casements. When undertaking these works obviously very little of your original window is left remaining and you can expect a higher level of finish. We would expect new sashes to be manufactured to a high level and installed into your casement and be freely moving. If your original casements are still in place there will be sideways movement in your sashes even after new sashes are installed as your casements may be bowed or twisted due to subsidence. We would expect draught-proofing to be in the region of 80% effective.
Full New Sash and Casement Replacement;
The highest level for window works. Your new casements will be completely mathematically square and your sashes should slide smoothly up and down. We would expect draught-proofing to be in the region of 90% effective.
This involves removal of shutters and panel work from your windows, this is the dustiest of the 3 options as there will be alot of historic soot and dirt behind the panelwork. The panelwork will be refitted but, you would expect a level of redecoration work. Paint seams will be cracked and a certain amount of remedial prep work will be required to bring them back up to a high standard,
Draughtproofing and ventilation
Draught-proofing is part of the above three services. The effectiveness of the draught-proofing has been broken down per section. It is ESC’s opinion that timber sash and case windows do not require trickle ventilation and there is enough ventilation and free movement of air around the sashes.
For example with a plastic window, when the window is new, the window will be probably 99% draughtproofed when all the rubber seals are engaged, this is reduced to 85-90% with the installation of trickle vents. Ventilation for windows is an essential part of condensation control. If you have a completely airtight window, condensation will be far higher.
The free movement required by the sashes in order to function properly allows enough ventilation. It should be noted that timber sash windows are a natural product and are subject to expansion, shrinkage and occasional twists within the timber. This is completely normal with any timber product, and should have no adverse affect on the windows.
We manufacture our own windows. They are traditionally made with haunched mortice and tenon joints in exactly the same manner as they were made originally. We run specialised mouldings and astrigals which are not available “off the shelf”.
This process is far more time consuming than the mass produced methods used by many companies, who sometimes use finger joints, metal plates in corners, and through tenons to speed up the production process. Moisture will always get into the joints of a window to some degree – snow build up on a cill for example, this will have no short term affect on a mortice and tenon joint, but joints which rely on glues or metal plates cannot possibly last. Windows produced in this manner have a far shorter life span, and we sometimes find ourselves replacing windows that are 5 -10 years old.
Properly made and maintained sash windows will last for years (see Saltoun hall refurbishment case study for 300 year old sash windows)
Double Glazed Units and Astrigal Width
We will always match the sash windows as close to the original as possible, from the moulding style to the proportions and astrigal width. However this style of window was not originally designed for double glazing so there has to be a certain amount of compromise when doing this. When windows have narrow astrigals, (less than 25mm) the cover on the edge of the spacer bar (ie the depth of the glass rebate) is very narrow, so the cover on the edge of the double glazed units is minimal. You will always see a certain amount of the spacer bar, 3-4mm is possible in some cases. The only way of avoiding this issue is to make the astrigal wider, which is normally not permitted in listed buildings or conservation areas.
With multiple astrigalled windows, where the units are quite small, the units are manufactured by hand as they are too small to be machine made, so a few millimetres variation in spacer bar sightlines is inevitable.
Having said all of that, when the windows are painted, the paint should always overlap onto the glass a few millimeters from the timber or putty bead to seal this join from water penetration. This will normally conceal most of the spacer bar.
We manufacture windows from any type of timber, but the most commonly used timber for sash windows is redwood. The timbers are hand picked and unsuitable sections are not used in the production process. However it should be noted that these windows are made from solid timber and not laminated sections, so movement in the timber, knots and minor shakes are to be expected in any solid timber product.
Visit the TRADA website for downloadable guides to all timber varieties.
We see windows of all ages and all timber types when we are undertaking our works, and in our opinion, many of the hardwoods last no longer than a good quality redwood. On jobs such as the Mission Home (see case studies) the oak windows had decayed far more than the original redwood windows.
All timbers have a moisture content and will therefore react differently in different environments.
ESC recommends using our own painting service. The painting of sash and case windows is a highly skilled undertaking and should be carried out at a minimum by a suitably qualified contractor. If windows are not painted correctly then the life span of them will be severely affected. Care should be taken to keep draught-proofing systems reasonably paint free.
Factory spray painting is also popular on mass produced windows, whilst this is convenient and cheaper, it is ESC opinion that this is an inferior painting method in particular with regard to the seal betwen the timber and the glass units when a slight overlap onto the glass is essential to seal the join.
We will normally knot seal, prime and undercoat the timbers in the workshop by hand, and the windows will then get a further undercoat and top coat applied on site.
The majority of the painters work is in the preparation of the windows, if you choose to use your own contractors or undertake painting work yourself, please be aware that preparation works will still be required before commencing any painting..
Please note that a start date for painting will be given after joinery works are completed . All painting works are subject to weather conditions and as such may not be undertaken immediately after installation of your windows. All painting works will be invoiced at a later date separately from joinery works which will be invoiced on completion of installation of windows. Please Note: gloss paint takes 7 days to dry. Sashes should be moved daily during this period to avoid them sticking.
ESC uses only the best quality ironmongery. When good enough fittings have not been available we have had them specially manufactured for us. The fittings are all replicas of the original Victorian and Georgian fittings and are usually made from solid brass except where extra strength is required such as with the pulley wheels where the main body would be made from steel and the face plate would be solid brass. The fittings are available in 3 finishes, Polished Brass, Chrome and Satin chrome. You will be asked to specify the finish you require prior to commencement of manufacture.
Please note that sash windows are sometimes sold by companies as maintenance free, unfortunately this is not the case. Sash windows require very little maintenance however, sash and case windows should be painted regularly to get a long life time from the product. Depending on the windows location and its exposure to sun and weather, the windows should normally be thoroughly painted every 3-4 years and cills and bottom rails every 1-2 years. More often may be required on for example seafront properties, where extreme exposure to elements and salt will break down the paint quicker. Linseed oil should be applied to sand mastic in order to stop it drying out and retain its flexibility.
Follow the link in the left hand column to Historic Scotlands excellent guide to sash and case window maintenance.
Shutters are a complex piece of joinery which involve multiple sections of timber locating together with very fine tolerances. Shutters are very effective for heat and sound insulation and as a replacement for curtains. However, due to the fact that original windows are rarely level and plumb and due to the natural movement in timber, a small amount of twisting in timber sections is normal and can be expected. When you combine multiple sections together they will very rarely meet completely and will never achieve complete blackout. This can normally be improved upon by the use of additional catches which often with time will pull the twists out of the timber.