Most people assume that installing sash windows is a single day’s work. A new installation goes through a survey step, a design step, a manufacturing step, and a fitting stage, with each phase lasting a different amount of time. Once a window is on site, it takes 1/2 to 1 day to install a single window and 2-5 days to replace an entire window system, depending on the number of windows installed. The larger time factor encompasses everything that happens before installation day, especially manufacturing, which is why most projects take approximately 6 to 10 weeks to complete. Here is a step-by-step explanation of timber sash windows installation.

Initial consultation and property survey

It is from here that the project starts, and the correct installation plan is confirmed.

  • Assessing existing windows A specialist visits the property to assess the condition of the existing frames, sashes, and surrounding structure. It will help decide whether full replacement or timber sash window repairs are the most appropriate option and flag any conservation area requirements early.
  • Measuring specifications and discussing requirements At this stage, the surveyor takes accurate measurements. There are standard sizes for timber sash windows, but most period properties will require custom-made sash windows. The surveyor also takes preferences for glazing, hardware finish, and any specific performance requirements.

Design and quotation stage

Then, the specification and cost of the timber sash window are finalised.

  • Selecting window styles and window finishes At this stage, the installer records the sash type, timber species, glass type, paint colour, and hardware type. Every decision directly affects both the appearance and the long-term performance of the window, so confirming everything here prevents costly changes later.
  • Receiving and approving the quote The installer will confirm the timber sash windows cost within five to seven working days of the survey. The prices hence depend on the size, type of glass, and finish. Check the quote thoroughly before booking the service to prevent any surprises later.

Manufacturing your timber sash windows

This is the longest step and takes up the bulk of the time.

  • Bespoke window production process Once the quote is approved, production is started. The manufacturer makes bespoke timber sash windows to the exact size agreed upon in the survey. The window generally takes four to eight weeks for manufacturing, all depending on complexity and lead time.
  • Quality assessment before delivery The manufacturer then inspects each window for sash operation, dimensions, glazing, and finish. Any issues found here are rectified properly.

New timber sash window installation process

This stage involves the work done on the site.

  • Firstly, the team takes out the old frame, sashes, and other hardware.
  • They check uncovered brickwork and plaster for dampness, rot, or cracks, and make all required repairs before installing the new window.
  • Next, they set the new frame into place in the opening, level and square it, then permanently attach it. They seal the outer edge to prevent any draughts between the timber and the wall.
  • Lastly, the team installs the sashes and checks each one to ensure smooth movement, proper locking, and a tight fit with the frame.

Final step of timber sash windows installation

This stage marks the end of the visible work and verifies that all the windows are functioning correctly.

The specialists seal the installation around the frame with an external sealant to weatherproof it. They repair all plaster and brickwork that may have been disturbed during the removal process and touch up the paintwork in the area.

They then thoroughly test the window before leaving, including testing the sash, verifying that the lock works as designed, checking the seal, and inspecting the window glazing. They resolve any problems immediately, so the window functions properly.

Typical installation timeframes

The duration of timber sash window installation differs from project to project.

It takes about half a day to a full day to install a single window, which includes removal, installation, and final inspection. It takes between 3 and 5 days for a full-house replacement of 6-8 windows, which is usually done in stages over several visits.

Several factors also extend the timeline, including brickwork or plasterwork, planning consent delays in conservation areas, and the specification of complex, bespoke timber sash windows.

Aftercare and maintenance recommendations

Once timber sash windows have been installed, you must follow the steps below for their aftercare and maintenance.

  • Don’t repaint the sashes for the first few weeks so the wood can settle.
  • It’s important to open and close the sashes often during this time as it helps the new seals to bed in properly.
  • Then do annual maintenance checks for early signs of moisture damage in the paint or finish.
  • Change sash cords when they begin to wear out, not when they break.

Doing this will minimise the need for future repairs and ensure the windows function efficiently for years to come.

Conclusion

Much of the time spent on a sash window project is spent before the window is installed. Manufacturing alone can take four to six weeks, so the fitting is the fastest part of the process. If you work around this, it will help you plan the rest of your renovation without being caught by surprise by a longer-than-expected lead time.

SJB Sash Windows, an experienced timber window company in London, provides a complete service from initial measurements until installation day. Contact us today to request a free quote for your project and learn the exact timeline.