Most homeowners are told "about eight weeks" and then feel misled when month four arrives. The honest answer is that the building work on a typical Croydon loft usually runs six to twelve weeks, but the whole project from first enquiry to signed-off, decorated room is more often four to seven months. Here is where that time actually goes.
For the terraced and semi-detached houses common around Thornton Heath, South Norwood and Shirley, a rear dormer conversion with one bedroom and an en suite typically takes eight to ten weeks on site. A simple Velux (rooflight only) conversion, where the existing roof shape is untouched, can be done in four to six weeks. An L-shaped dormer over a back addition, or a hip-to-gable on a 1930s semi, tends to run ten to fourteen weeks because there is far more structural work and more scaffolding time.
Roughly, the on-site sequence looks like this. Knowing the order helps you spot when things are genuinely slipping rather than just looking chaotic.
This is where most of the calendar disappears. Around 80 to 90 per cent of Croydon lofts fall under permitted development, so no planning application is needed, but you will still want a Lawful Development Certificate from Croydon Council for when you sell. That takes around eight weeks to determine. If your property is in a conservation area such as Park Hill or Upper Norwood, or permitted development rights have been removed on your street, you need full planning permission: budget eight to ten weeks, longer if it goes to committee.
Building control is separate and non-negotiable. Structural calculations for the steels take one to three weeks from an engineer, and you can usually book building control inspections with a week's notice. If you share a wall with a neighbour, which almost every Croydon terrace does, the Party Wall Act applies. Serve notice at least two months before work starts. If neighbours consent in writing you are done; if they dissent, appointing surveyors and agreeing an award adds four to eight weeks and a bill of roughly £1,200 to £2,500.
Genuine delays are rarely mysterious. In our experience the same handful of things account for most of them, and several are within your control if you decide early.
Yes, and most people do. For the first several weeks the loft is sealed off and access is via scaffolding, so disruption is limited to noise and dust. The genuinely disruptive phase is the two to four days when the staircase opening is cut through your existing ceiling. Expect dust throughout the house, no upstairs landing lighting for a day or two, and a temporary boarded opening.
If your water tank sits in the loft, allow for a day without hot water while it is removed and the system converted to a combi or unvented cylinder. Plan that around work and school where you can.
Usually the full duration of the roof and external work, so around five to eight weeks for a dormer. It comes down once the roofing, guttering and any rendering or tile hanging are finished and signed off.
No, legally you can start as soon as you are satisfied the work is permitted development and building control is in place. Most people apply in parallel and have the certificate in hand well before the build finishes, which is fine for a future sale.
Often because some include design, structural calculations and decoration in the figure and others quote only the on-site build. Ask each builder specifically what their stated weeks cover and whether the price includes plastering, staircase and en suite fit-out.