Replacing a rooflight in a finished loft room

Working from outside

Wherever access allows, the job is done from the roof. Tiles lifted, old unit out, new unit in, flashing fitted, tiles reinstated.

That keeps almost all of the disturbance outside the room. The internal work is then limited to the junction between the new frame and the existing reveal.

The reveal

The finished plaster surface between the frame and the room. On a like for like replacement it usually survives, with a fresh line of filler and caulk where the new frame meets it.

You will want to repaint the reveal, because the old paint line will not match the new frame position exactly.

Where the size changes, the reveal is cut back or packed out on the affected sides, reboarded and skimmed, which means drying time and decoration.

Dust

There will be some. Cutting plaster and lifting an old frame releases decades of dust from the void around the opening.

We sheet the room and the floor, and clear up. Moving furniture and soft furnishings out first is worth doing.

Weather

The roof is open for a few hours, not days, and it is made watertight before we leave whatever stage the job has reached. On a forecast of driving rain we move the date rather than working through it badly.

Furniture beneath

Clear the area under the window. Small pieces of old mortar and mastic come down when a frame is removed, and it is easier to move a bed than to protect one.

Loft insulation

In a converted loft the insulation is usually at rafter level around the opening. Where it has been compressed or is missing at the perimeter, replacement is the moment to correct it, and it costs little while the opening is exposed.

What makes this different from a bare loft

Everything about the work is the same on the roof. What changes is that there is a finished room underneath, with plastered reveals, decoration, flooring and furniture, and all of it has to survive the job.

Most of the cost difference between replacing a rooflight in a converted loft and replacing one in a bare roof space is inside rather than outside.

Protection comes first

Before anything is opened. Floors covered, furniture moved out or sheeted, and a dust barrier at the door of the room.

The making good is where the mess comes from rather than the roof work, and in a finished room that mess has somewhere to go. Plaster dust travels, and it travels through a house rather than settling politely in a loft.

Where the loft room is reached through other rooms, the route is protected too, because materials and the old unit have to come out that way.

The reveal, which is the real work

In a bare loft the frame is fixed and that is largely the end of it. In a finished room the lining has to come off, and putting it back is a plastering and decorating exercise.

The lining comes off far enough to expose the frame and the structural opening, which is further than the visible reveal. That is unavoidable: the frame is fixed through into the structure and the insulation collar sits between the two.

It goes back as plasterboard cut to the reveal, taped and skimmed, left ready for decoration.

Where the room has a distinctive finish, Artex, a textured plaster or a decorative coving running close to the opening, the repair is harder to disguise and that is worth flagging at survey rather than discovering.

The opportunity while it is open

Two things worth doing at this point, because the reveal is off and it will not be off again for twenty five years.

Fit the insulation collar, if the original installation did not have one. On a loft conversion of the 1990s it frequently did not, and that is why the reveal has been running with condensation every winter.

Splay the reveal. If the original was boxed square, cutting it back at an angle at the head and the sill opens the beam of light out and can make the same window feel considerably larger.

It costs a little more in plastering, which is being done anyway, and it is the best value improvement available on the whole job.

Drying and decoration

The part that catches people out on timing.

New plaster needs to dry before it is painted, and in a cold house that takes longer. The room is finished but not decorated at the end of the job, and in winter that gap is longer still.

We say so at booking rather than leaving it as a surprise, and it is worth planning the work when the room can be out of use for a period rather than the day before you need the bedroom back.

Decoration is not included unless specifically asked for, and where the room has a colour you cannot match, it is worth having a tin ready.

The escape question, which may have changed

The one thing that genuinely differs from replacing a rooflight in an ordinary room, and it is easy to miss.

In a habitable loft room, Building Regulations frequently require the roof window to serve as a means of escape. That brings a minimum clear openable area, minimum opening dimensions, and a maximum height of the bottom of the opening above the finished floor.

If the existing window carries that duty, the replacement has to as well.

The trap is opening type. A centre pivot window sits across the middle of the aperture when open and frequently fails the clear opening requirement, where a top hung unit that swings clear satisfies it. Replacing a top hung escape window with a centre pivot unit because you liked the cleaning feature can put a compliant room out of compliance.

Establish whether the window carries the duty before choosing, and check the specific model’s published clear opening figures against the requirement in writing rather than assuming any top hung unit will do.

Obsolete sizes, which are likely here

A great many loft conversions were done in the 1980s and 1990s, and sealed units last fifteen to twenty five years, so those windows are arriving now.

Size ranges have changed since, so expect the code to be obsolete. Photograph the data plate on the sash rather than measuring: it is on the top edge or on the frame beside the hinge, and on a centre pivot window rotating the sash brings it into view.

Three routes. Adapt the opening to the nearest current size, usually within 40mm or 60mm, which is invisible when finished and leaves a standard size for the future. Find another manufacturer at the old dimension, which suits an opening that is awkward to alter. Or reframe entirely.

What nobody should do is force a unit into an opening it does not fit and pack the difference, which survives about a year before the frame goes out of square.

In a finished room, adapting the opening is a smaller step than it sounds, because the reveal is being replastered regardless.

Access from outside

A loft room window is by definition high, so this is scaffold rather than tower work on most houses.

That is a real line on the quotation and it is the reason the same window costs different amounts on different properties. Where the scaffold has to stand on a pavement, a highway licence is needed with a fee and a lead time.

It is also the strongest argument for doing all the windows on the slope at once. Access is a fixed cost shared across everything done in the same visit, and units fitted at the same time fail at about the same time, so the others are coming anyway.

What the room is like during the work

Out of use for the day, and cold while the opening is out. On a like for like replacement the roof is open for a matter of hours rather than days, and we close up before we leave.

An opening is never left uncovered overnight, and a strip out does not start if the forecast will not allow the roof to be closed the same day.

Where two or three units are being done, that is two to three days rather than three separate days, because the access and the setting up are shared and the second and third go faster than the first.

Worth doing at the same time

If you are ever going to want a motorised opener on a high loft window, this is the moment to run a capped cable to it, because the reveal is open and the plastering is being done.

Twenty minutes of work now, terminated in an accessible enclosure, and it turns a future upgrade from a disruptive job into a cheap one. Photograph where it is before the plasterboard goes back.

What makes this different from a building site

Everything below the opening is finished. Carpet or timber floor, decorated walls, furniture, and frequently a room somebody sleeps in.

The work itself is the same. The protection, the sequencing and the making good are not, and they are where the cost and the disruption sit.

Protection, properly done

The room cleared as far as possible, and whatever cannot be moved sheeted and taped rather than draped.

Floor protection over the whole room, not only under the opening. Dust travels further than people expect, and a rooflight opening rains debris the moment the ceiling is cut.

A dust sheet screen at the door, because the alternative is fine plaster dust through the rest of the house.

Any of this that is not in the quotation is worth asking about.

The plaster is coming off regardless

The reveal lining is fixed to the frame or hard against it, so removing the unit takes the plaster with it at the junction. That is true even on a like for like replacement.

Which means making good the reveal is a certainty, and realistically the ceiling gets repainted wall to wall rather than patched, because a patch on aged paint rarely disappears.

Fresh plaster needs to dry before decoration, so the room is usable but not finished on the day, and in cold damp conditions that takes longer.

Use the moment

The reveal is open for the only time in twenty five years.

Insulation carried continuously around all four faces, meeting the frame. The vapour control layer taped to the frame. An insulation collar outside. And if you have ever wanted the reveal splayed to spread the light better, this is when it happens.

Ask for photographs before the plasterboard goes on, because none of it can be verified afterwards.

Consider going bigger while it is open

Extending the opening up the slope, between the same rafters, cuts nothing and costs comparatively little on a job that is already happening.

The reveal is being rebuilt either way. If the window has always been too small or badly placed, this is the cheap moment to change it.

The escape question

Where the loft has become a bedroom since the original window went in, check whether an escape window is now required, because a centre pivot unit that was acceptable before may not satisfy it.