Sequencing a replacement around the weather

How long the roof is actually open

For a like for like replacement, a few hours. Old unit out, opening checked, new unit in, flashing fitted, tiles reinstated.

Not a day, and certainly not overnight. The roof is made watertight before we leave, whatever stage the job has reached.

What we watch

Driving rain is the one that matters. Not drizzle, which is workable, but sustained rain arriving horizontally.

High wind. Handling glass at height in gusts is unsafe, and a sheet of glass is an effective sail.

Ice on the roof. A safety matter rather than a quality one.

Cold alone is not a problem. Sealants and tapes have working temperature ranges and we use products rated for the conditions.

We move dates

Rather than work through weather badly. A rescheduled visit is an inconvenience; a roof opened in driving rain is water in a ceiling and a detail rushed.

That is worth knowing when we call to move a date at short notice: it is the right decision rather than a lack of organisation.

Winter advantages

Shorter lead times, because it is a quieter season. And a failing rooflight is at its worst in winter, so the improvement is immediate rather than theoretical.

Larger jobs

Where a kerb is being rebuilt or an opening enlarged, the roof is open longer and the weather matters more. Those are the jobs we prefer to schedule with a settled forecast, and we will say so rather than starting and hoping.

The rule that governs everything

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

That is the whole of our weather policy and it is not negotiable. In this part of the country it occasionally costs us a day. It has never cost a customer a ceiling, and we would rather move a date than take a risk with an open roof.

Why a rooflight job is weather sensitive at all

Because there is a period, usually a few hours on a replacement, when the roof is genuinely open. The old unit is out, the covering is lifted around the opening, the underlay is cut, and the only thing between the room and the sky is temporary sheeting.

Temporary sheeting works. It works less well in sustained rain and it works badly in wind, which is the real constraint.

On a new opening that period is longer, because structure has to be cut and trimmed before the frame goes in. On a lantern it is longer again.

Rain is manageable, wind is not

This is the part that surprises people, because rain is what they worry about.

Working in light rain is normal and the sequence is planned around it: the frame goes in and the weathering is completed rather than the roof sitting open while it passes.

Sustained high wind stops roof work outright. Handling glazing at height becomes unsafe, sheet materials become unmanageable, and temporary covering will not stay put. A large sealed unit is a sail before it is a window.

So a forecast of a wet day may be workable and a forecast of a windy one is frequently not, which is the opposite of what most people expect when a date moves.

Frost, and old coverings

Slates and old clay tiles are more brittle in hard frost, and a higher proportion breaks on removal.

On a modern concrete tile roof that is a minor consideration. On a historic roof where matching weathered handmade tile is genuinely difficult, it is worth waiting for milder weather rather than losing tiles that cannot be replaced like for like.

We will say so rather than pushing on, and on a listed building where the covering is part of what is significant, we will say so firmly.

How a day is sequenced

The order exists so that the roof reaches a watertight state as early as possible and stays there.

Protection first, inside. Floors covered, furniture moved or sheeted, dust barrier at the door. This happens before anything is opened, so that if the weather turns during the strip out the room is already protected.

Strip out and inspection. Lining off, old unit out, covering lifted, timber inspected. This is the point of maximum exposure and it is kept short.

Frame in and squared. Once the frame is fixed the opening is substantially closed even before the weathering is complete.

Weathering, in order: underlay collar dressed and lapped, flashing kit fitted, covering reinstated over the flashing. At the end of this the roof is watertight and everything remaining is internal.

Insulation collar and lining, which can proceed regardless of what the weather does.

That structure means the weather sensitive portion of a one day job is the first half, and by early afternoon on a replacement the roof is normally closed.

Multi day jobs

Where the work runs to several days, each day is planned to finish watertight rather than half done.

On a new opening, that may mean forming and trimming the opening and getting the frame in and temporarily weathered on day one, with the covering properly reinstated on day two. What it does not mean is leaving structure open under sheeting overnight because the sequence ran late.

On a lantern, where the opening is large, the same principle applies with more care. We will not form a lantern opening at all unless the forecast allows it to be closed and made watertight the same day.

Winter working

Entirely normal and there is no seasonal premium. Three practical differences.

Shorter days. A job that fits comfortably into daylight in June is tighter in December. On a single replacement that rarely matters. On a larger job it means the work is broken into stages that each finish watertight.

Drying times. Plaster takes longer to dry in a cold house, so where making good involves plastering the room is finished but not decorated at the end of the job, and that gap is longer than in summer. That is scheduling rather than quality, and we say so at booking rather than leaving it as a surprise.

Availability. Winter is quieter than spring through early autumn, which is when people plan extensions and conversions. If you are flexible on timing it is worth asking what dates we have.

Against those, the improvement is at its most obvious. A unit fitted twenty five years ago has no low emissivity coating, no argon, an aluminium spacer and no solar control. Replacing it in November means the room is noticeably warmer for the rest of the winter, and the band of edge condensation an aluminium spacer produces disappears entirely.

If a unit has already misted, waiting until spring means another winter of a cold, obscured window for no benefit.

Scaffold and the weather

Scaffold is erected and struck around the fitting rather than on the same days, which adds two visits to the programme and gives some flexibility: the working days can move within the period the scaffold stands.

Where the scaffold is on the highway under a licence, that period is fixed by the licence and moving it is not free. On a terraced property with a pavement licence, weather delays are therefore more expensive than on a house with a driveway, which is worth knowing when a date is offered in February.

When water is already coming in

Say so at the enquiry and we will treat it as urgent rather than putting you in the queue.

Very often the right first step is not the replacement at all. Making the roof watertight temporarily buys the time to establish what the unit actually is, whether the size is still made, and what the options are, rather than ordering in a hurry and getting it wrong.

A temporary repair costs very little and it converts an emergency into an ordinary job that can be scheduled properly.

What we will tell you at booking

A realistic date rather than an optimistic one, booked to a confirmed delivery date for the unit rather than an estimate.

That a date may move by a day for wind or hard frost, and why. And on a job with plastering, that the decoration follows later and that in winter it follows later still.

A date you can plan around is worth more than one that moves twice.

What the forecast has to tell you

Three things, and rain is the least important of them.

Wind speed and gusts. This is what cancels days. Working at height in a gale is unsafe, and handling a glazed unit in one is dangerous. A crew that cancels on a windy day with clear skies is doing the right thing.

Overnight temperature. Frost on a covering makes a roof treacherous and makes old clay and slate far more likely to break on removal.

Whether there is a dry window long enough. Not whether it will rain at all, but whether there is a stretch long enough to strip, form the opening, fit and reinstate.

Keeping the opening covered

A competent crew sheets the opening whenever they are not actively working on it, not only when it starts to rain.

That means a tarpaulin weighted and secured against wind rather than laid on, and it means the covering going back before the crew leaves rather than being left for the morning.

Inside, the room is cleared and sheeted before anything is cut, because a rooflight opening rains debris into the room the moment the ceiling is opened.

Building a contingency into the booking

Weather cancellations are normal on roof work and they are far easier to absorb if the programme allows for them.

A crew with a spare slot the following week can reschedule; one booked solid for six weeks cannot. Ask about that when the date is set.

And confirm the unit has arrived before the access goes up. Scaffold standing idle while a delivery is chased is the most expensive kind of delay there is.

The materials that need a temperature

Sealants and adhesives have minimum application temperatures, and working below them produces a joint that never achieves its designed properties.

A good installer works within them, which occasionally means a detail waits for a warmer day rather than being forced. That is a sign of competence rather than delay.

Why winter still works

The trade is quieter, scaffold is easier to book, and dates are more flexible than in summer when everybody wants the same weeks.

A failed unit is losing you heat exactly when it costs most, so the benefit is immediate.

The trade is a longer plaster drying period and a greater chance of a cancelled day, both of which are manageable if they are expected.