Can you lay bricks in winter?

Yes, within limits. The rule of thumb used across the industry and by Hertfordshire Building Control is that bricklaying should stop when the temperature is 3°C and falling, and should not restart until it is 3°C and rising. Below that, mortar will not gain strength properly and any water held in the joint can cause frost damage. New masonry also has to be protected overnight with polythene or hessian, and in severe cold with insulation board or heating.

Is it more expensive to build in winter?

The build itself is not usually priced differently, but winter adds cost in small ways: temporary protection and sheeting, site lighting, occasional lost days, and longer drying times that can hold up the trades behind. Against that, autumn and winter are quieter for most builders, so availability and start dates are often better than in spring.

Does concrete set in cold weather?

It does, but it needs care. Ready-mixed concrete should not be delivered below 5°C, and site-mixed concrete can be used down to around 2°C provided the ground is not frozen. Concrete must never be poured onto frozen ground, and fresh pours need protecting while they cure. In severe frost, insulation alone is not enough and heating is required.

Should I wait until spring to start my extension?

Usually not, if what you mean is waiting to start the process. Planning has a statutory eight-week determination period for householder applications and commonly takes eight to twelve weeks in practice, so an application submitted in October is typically decided by the new year and ready to build in spring. Waiting until March to begin the paperwork means building in autumn instead.

What building work can still be done in the middle of winter?

Most of it, once a building is weathertight. Loft conversions are largely internal work under an existing roof. Garage conversions, internal structural work, carpentry, joinery, fitted wardrobes and bespoke kitchens are all essentially season-independent. It is the wet trades outdoors — foundations, brickwork, roofing — that the weather genuinely governs.

How much does winter slow a build down?

Less through cold days lost than through daylight and drying. London and Hertfordshire get under eight hours of daylight around the winter solstice against more than sixteen in June, which shortens the working day, and screed, plaster and paint all take materially longer to dry in cold, damp conditions. A realistic winter programme allows for both rather than assuming a summer pace.

Building Through Winter: What Actually Slows a Job

Every year from about the middle of September we get the same question, usually phrased as a decision already made: "We'll leave it until the spring now, won't we?" Sometimes that is the right call. More often it is a six-month delay bought on a misunderstanding of what winter actually does to a building site.

Cold weather stops less than people expect. Daylight and drying times stop more. And the paperwork — the part that genuinely governs when you can start — runs at exactly the same speed in January as in June, which is the strongest argument for doing something about it now rather than in March.

What Genuinely Stops in Cold Weather

Three things are properly weather-dependent, and they are all outdoor wet trades.

Masonry. Bricklaying should stop when the temperature is 3°C and falling, and should not restart until it is 3°C and rising. This is the guidance Hertfordshire Building Control publishes and it is the figure any competent bricklayer works to. The reason is not comfort: mortar needs warmth to gain strength, and water trapped in a green joint expands when it freezes and damages the work. New walls also have to be covered overnight with polythene or hessian, and in a hard frost with insulation board or heating.

Concrete. Ready-mixed concrete should not be delivered below 5°C. Site-mixed concrete can go down to around 2°C, but only if the ground is not frozen — concrete poured onto frozen ground will fail as the ground thaws beneath it. Fresh pours need protecting while they cure, and in severe frost insulation on its own is not enough.

Roofing and anything at height. Less a temperature limit than a wind and ice limit. Scaffolding in a gale is a stop-work decision, and it is made on the morning, not in the programme.

What this means in practice is that a hard cold snap costs a few days, not a season. A well-run site works around it: the wet trades pause, the internal work continues, and the programme absorbs it.

What Barely Notices

Once a building is weathertight, most of what is left is indoor work under a roof with the heating on. That covers a great deal more than people assume:

Loft conversions — largely internal work beneath an existing roof. Only the initial opening-up and any dormer construction are genuinely exposed, and those are a small share of the programme.
Garage conversions — the structure is already there and already covered.
Internal structural work — steels, openings, chimney breast removal. Indoors throughout.
Carpentry and joinery — fitted wardrobes, alcove units, bespoke kitchens, staircases. Essentially season-independent.
Second fix generally — electrics, plumbing, decorating.

An extension is the mixed case. The groundwork and shell are weather-governed; everything after the roof goes on is not. Get a build watertight before Christmas and the rest of the winter is largely indoor work.

The Real Constraint Is Daylight, Not Temperature

This is the part that surprises people, and it is the one that actually shows up in the programme.

Around the winter solstice, London and Hertfordshire get under eight hours of daylight. In late June it is more than sixteen. Even allowing for site lighting, which works well indoors and poorly on a roof or in a trench, the usable outdoor working day in December is roughly half what it is in midsummer.

Add the practical constraints and it tightens further. Most local authorities restrict construction hours — commonly around 8am to 6pm on weekdays with reduced Saturday hours and nothing on Sundays — so a builder cannot simply start earlier to recover the light. In December, permitted hours and available daylight barely overlap at the start and end of the day.

A realistic winter programme prices this in. One that assumes summer productivity will slip, and the slippage gets blamed on the weather when the cause was arithmetic.

Drying Times — The Part People Forget

Cold, damp air holds less moisture and moves it more slowly. Everything wet therefore takes longer, and each delay pushes the trade behind it back:

Screed needs substantially longer before floor coverings can go down, and rushing it is how you get a failed floor finish.
Plaster takes longer to dry out before it can be decorated. Painting plaster that is not ready traps moisture and the decoration fails.
Paint itself has minimum application temperatures, and most emulsions do not perform below about 10°C.

This is where winter genuinely costs time, and it is almost always underestimated. Heating and dehumidification help and are worth budgeting for, but they do not make the problem disappear. If a programme has plastering and decorating stacked back to back in January, it is optimistic.

Ground and Groundwater

Much of Hertfordshire and north London sits on clay. Clay in February is not the same material it is in July: waterlogged ground is harder to excavate, harder to get a machine onto without damaging the garden, and trenches are more prone to collapse and need more support.

None of this is a reason not to build. It is a reason for the groundworks to be programmed with realistic contingency rather than the same allowance you would make in May, and for the site set-up — access boards, spoil storage, drainage — to be thought about before the digger arrives rather than after.

Why Autumn Is the Right Time to Start the Paperwork

Here is the argument that actually matters, and it has nothing to do with the weather.

The consent process runs at the same speed all year:

Planning has a statutory eight-week determination period for householder applications, and eight to twelve weeks is the realistic range once validation and any queries are included. See our guide to planning permission in Hertfordshire, and note that in a conservation area or under an Article 4 direction the picture changes.
Party wall notices require two months for work to a party structure. Serving them early so the period runs alongside the planning application is the single easiest way to protect a start date — see our party wall guide.
Building regulations approval and inspection scheduling take their own time, covered in our building regulations guide.

Run those numbers forward. An application submitted in October is typically determined around the new year, with party wall periods already served and expired, ready to build in early spring. The same decision deferred to March means starting the process in spring and building in autumn — which is how a job intended for one summer lands in the next.

One caveat worth knowing: council planning departments slow over Christmas. Two weeks of closure inside an eight-week determination period is a meaningful proportion of it. Submitting in early autumn rather than late November keeps the decision clear of that.

What to Ask Before a Winter Start

If you are considering starting work between October and March, these are the questions worth asking:

When will the build be weathertight? This is the single most important date in a winter programme. Everything after it is largely indoor work.
What protection is allowed for in the price? Sheeting, temporary roofs, frost protection for new masonry and site lighting all cost something. You want them in the quote, not raised later as an extra.
How have drying times been programmed? If screed, plaster and decoration are sequenced as though it were June, the programme is wrong.
What happens on a stop-work day? A good answer describes which internal work moves forward instead. A vague one means lost days.
Is the groundwork contingency seasonal? Wet clay deserves a different allowance from dry summer ground.

The Honest Summary

Winter is a genuine constraint on foundations, brickwork and roofing, and it lengthens every drying time in the build. It is close to irrelevant for loft conversions, garage conversions, internal structural work and carpentry, and it makes no difference at all to how long the council takes.

The right question is rarely "should we build in winter?" It is "what should we be doing in winter so we can build when we want to?" For most households the answer is design, consents and notices now, construction in spring — and that only works if the paperwork starts in autumn.

Frequently Asked Questions

Can you lay bricks in winter?
Yes, within limits. The rule of thumb used across the industry and by Hertfordshire Building Control is that bricklaying should stop when the temperature is 3°C and falling, and should not restart until it is 3°C and rising. Below that, mortar will not gain strength properly and any water held in the joint can cause frost damage. New masonry also has to be protected overnight with polythene or hessian, and in severe cold with insulation board or heating.
Is it more expensive to build in winter?
The build itself is not usually priced differently, but winter adds cost in small ways: temporary protection and sheeting, site lighting, occasional lost days, and longer drying times that can hold up the trades behind. Against that, autumn and winter are quieter for most builders, so availability and start dates are often better than in spring.
Does concrete set in cold weather?
It does, but it needs care. Ready-mixed concrete should not be delivered below 5°C, and site-mixed concrete can be used down to around 2°C provided the ground is not frozen. Concrete must never be poured onto frozen ground, and fresh pours need protecting while they cure. In severe frost, insulation alone is not enough and heating is required.
Should I wait until spring to start my extension?
Usually not, if what you mean is waiting to start the process. Planning has a statutory eight-week determination period for householder applications and commonly takes eight to twelve weeks in practice, so an application submitted in October is typically decided by the new year and ready to build in spring. Waiting until March to begin the paperwork means building in autumn instead.
What building work can still be done in the middle of winter?
Most of it, once a building is weathertight. Loft conversions are largely internal work under an existing roof. Garage conversions, internal structural work, carpentry, joinery, fitted wardrobes and bespoke kitchens are all essentially season-independent. It is the wet trades outdoors — foundations, brickwork, roofing — that the weather genuinely governs.
How much does winter slow a build down?
Less through cold days lost than through daylight and drying. London and Hertfordshire get under eight hours of daylight around the winter solstice against more than sixteen in June, which shortens the working day, and screed, plaster and paint all take materially longer to dry in cold, damp conditions. A realistic winter programme allows for both rather than assuming a summer pace.

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