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Repair & Restoration

windows & doors

Rotten, draughty, hard to operate sliding windows? We can help.

If your charming old windows or doors look ready for the scrap yard, think again!
Rotten, draughty, unsightly windows or doors? Our restoration service is tailored for you.
Design Build Joinery explains the process of repair

If you love the period charm and heritage innate in your wooden sliding sash windows but hate the draughts, rattles, rot and heat loss that can also be part and parcel with an older property then you need help from the experts. With over many years’ experience repairing windows across the London, you can trust Design Build Joinery.

The replacement of sash windows is, in many cases, completely unnecessary. There are very few instances where damage and decay cannot be repaired using the right knowledge and tools. Repair work will depend on the damage. Decaying timber, broken sash cords, damaged pulleys and broken glass, will all need replacing.


Traditional timber sash windows are an essential feature of a period buildings character. Therefore it is vital to retain them, not only because of the aesthetic appeal, but because they add value to your property. Also known as a sliding sash or vertical sliders, they rely on a weighted system that allows the heavy sashes to lift and fall with ease. In order for the sashes to move in the box and operate smoothly, there is a 3mm gap between the sash and the frame which is often the cause of draughts, rattles, dust and rain ingress and heat loss. 


Our service focuses firstly on window repair and secondly on upgrading their performance.

What happens during the renovation process?
  1. Windows are carefully removed from the window frame.

  2. if necessary The glass is removed and then the old putty can be scraped away.

  3. Any decaying timber in the units, frame or sill is routed out to expose the “sound” timber.

  4. The joints are cleaned and any rotten wood is routed out.

  5. Occasionally, new timber is spliced in or replaced where the existing timber is beyond repair.

  6. Our unique epoxy resin, VR90, is used to fill the cavities and is moulded to match the existing profile of the timber.

  7. The sash and Frame are sanded or we burn the paint and always primed.

  8. The windows are then upgraded by fitting Brush Parting bead and draughts proof Sealing System

  9. The window is finished and painted by Dulux Weathershield Exterior paint.

  10. Sash cords or chain & pulleys are replaced, New Hardware Fitted and the sashes correctly balanced to ensure smooth operation of the windows.

  • We also work on casement windows and other timber windows and doors. Such diversification and decades of experience have made us the UK’s leading period window specialists.

Glazing Requirements

Many want to know if they can have new double-glazed units fitted into their existing timber sashes. The advice is to be careful — these windows were never designed to take two panes of glass, each thicker & heavier than the original.

The glazing bars in old sash windows are often not deep enough to take sealed double-glazed units, which ultimately leads to premature misting. we can do but we not recommended !!

Another option is to have new sashes made to fit your existing frames and to match the originals. DBJ use new slim glazing units and traditional methods of carpentry for an authentic look.

Costs of repairing sash windows

Prices will vary based on the extent of the damage also It depends on how much work each window needs:


  • For a recondition and new draught seals (this included stripping, priming and painting) = costs approximately £300-£500 per window inc Frame & Architrave.

  • Double-glazed sash replacements only, to fit into existing frames = approximately £500 per sash

This is just an estimate though, and we do offer a free no-obligation survey and quotation so we can come and see the windows and talk you through our service and the best options available to you. Our quotation gives you a full price breakdown, window by window.

Refurbishment Benefits
  • No more draughts

  • No more rattles

  • Reduced external noise levels

  • Improved insulation and thermal efficiency

  • Reduced dirt and dust

  • Correctly hung windows that operate smoothly

  • Extended window life

  • Improved security

  • Add value to your property

Our timber window repair services are excellent quality and value, but we will only recommend them to you if we believe they represent a good long-term investment. If your timber windows or doors are beyond repair we will always recommend partial or full replacement.

  • Q.Are your new double glazed sashes fully compliant with building regulations?
    Our complete new windows and doors comply with Document L Building Regulations. New sashes, casements or doors fitted into their existing frames do not have to comply as this type of work is classed as refurbishment and does not require certification. Listed buildings and some properties in conservation areas are exempt from Document L, and your local authority planning department will be able to advise.
  • Q:Is timber prone to movement?
    Timber’s beauty comes from the fact it is a natural material, and as a natural product some degree of movement in terms of expansion/contraction can be expected. However, with the timber that we use, this movement is kept to a minimum.
  • Q.Do timber windows warp over time?
    Low quality timber windows can warp over time, however, DBJ wooden windows are engineered to add strength, eradicate knots and resist twisting also we are confidently able to give a Comprehensive 10-year guarantee on all windows and doors.
  • Q.How often do timber windows need to be redecorated?
    We use 4 layer weathershield paint and stain finishes on all of our timber products to keep them looking good, however timber products aren’t maintenance free and will require regular maintenance to maintain the performance and look of the product. The regularity of maintenance will depend on the location of your property and where the wooden windows are located on the property. Our paint finishes will require maintenance every 3 years to 4 years in a moderate climate (non-coastal areas at low altitude) or every 2 to 3 years in extreme climates (coastal areas and high altitude). Our stain finishes will require maintenance every 2 to 3 years in a moderate climate (non-coastal areas at low altitude) or every 1 to 2 years in extreme climates (coastal areas and high altitude). Unsheltered windows will require more maintenance than those sheltered or partly sheltered. We recommend that the surface coating is inspected annually and if required you should re-coat the wood with stain or paint.
  • Q.Is there an alternative to timber windows that provide the traditional look?
    No, we don't supply uPVC windows actually that's not traditional look at all
  • Q.What glass options can I choose from?
    You can select from five different types of glass with our timber windows. These are: obscure, decorative, security, safety or anti-sun.
  • Q.Can I have safety locks fitted so the windows only partly open?
    Yes, for added safety we can fit safety locks to our timber windows so they only open as far as you want them to.
  • Q.I already have timber windows; will my entrance door match?
    If you have timber windows from us we can certainly match the colour of your timber windows. If not, with a range of colours available, we are sure we will be able to get a consistent look to your home.
  • Q.What is your lead time for new joinery or replacement sash windows and doors ?
    For items which we supply and fit our lead time on all products is between 3 to 7 weeks, and depends on how busy we are (during the busy summer months our lead times can stretch). the lead time only begins once a Purchase Agreement has been signed and your deposit has been received.
  • Q.Can you match the style of my existing windows?
    Yes. We are proud to be able to match most styles and patterns with our Classic range. If you require specific, historically accurate windows, replicating the existing features, this can be done for a higher price. Through modern technology and traditional joinery techniques we are able to produce elegant yet energy efficient replacement windows and doors.
  • Q. Where are your windows made?
    All of our new windows and doors or stairs are manufactured by our expert craftsmen in our workshops in North London. If you would like to visit our workshops to see the windows being made, please contact us on 08001303003 to arrange an appointment.
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