Specifying timber windows to a developer's budget: where the cost really sits

Are timber windows expensive? The honest answer is that it depends far more on how they are specified than on the material itself. For developers weighing margin against saleability, timber can look like a premium you cannot justify - until you see where the cost actually sits, and how much of it you control. This guide shows you the levers.

The question behind the question

When a developer asks whether timber windows are expensive, the real question is whether the return justifies the outlay. It usually does. Well-specified timber windows lift buyer appeal and hold their value across a scheme, as our developer's guide to premium timber windows sets out. But that value case only lands once the price feels reachable. So before the value conversation, it pays to understand what actually drives the number on the quote.

What a new build scheme requires before cost enters the conversation

Developer and multi-plot work is predominantly new build, and new build narrows the specification before budget does.

Windows in new dwellings in England have to answer Approved Document L, and under Approved Document Q they have to meet PAS 24:2022+A1:2024. Our Conservation range is manufactured to both. For new build work it is the range to specify.

U-values are published product by product rather than as a range-wide figure, and calculated using the detailed method in BS EN ISO 10077-2 rather than the simplified method in Part 1 that much of the market relies on. Ask which method sits behind any figure you are comparing, because the two are not directly comparable.

Where the cost in a timber window really sits

The main levers are:

Bespoke sizes and profiles. Non-standard sizes and intricate mouldings add hand-work at every stage of manufacture; standardising where the design allows takes that hand-work back out.
Timber selection. Engineered softwood suits most painted finishes and is the more economical choice. Hardwood earns its cost where an exposed, stained grain is part of the design.
Glazing and finish. Specialist glazing and complex colour specifications carry a premium; a considered, simpler palette holds cost without touching quality.
Ironmongery. Standard patterns cost less than bespoke or heritage patterns.

The point for a developer is control. The same premium product, specified simply and consistently across a project, sits at a very different price to one loaded with bespoke detail on every plot.

Overheating: the cost lever most schemes underestimate

Approved Document O applies to new residential buildings in England, and it is where a window schedule can quietly move the cost of a scheme.

There are two routes to compliance. The simplified method sets maximum glazed areas, varying with orientation, location and whether the dwelling has cross-ventilation, together with a minimum free area of opening to remove excess heat. The alternative is dynamic thermal modelling following CIBSE TM59, which gives the design team more flexibility and costs more to produce.

Three consequences land on the window schedule. Single-aspect apartments frequently fail the simplified method, which pushes those plots towards modelling. Meeting the free area requirement often calls for larger openable lights or a different opening type than the elevation first assumed, because free area depends on how a window opens and how far, not on its size alone. And windows that open beyond a certain point bring in the requirements for protection from falling, covering handle reach and cill or guarding height, which affect hardware and restrictors plot by plot.

Settle the window schedule against Approved Document O before it is priced. Resolving it afterwards is a change to every plot it touches.

Standardise, and the scheme gets easier to build

This is where multi-plot work rewards early decisions. Specifying a consistent window across a development - standard sizes, a shared profile, one finish - changes what the manufacturer is being asked to make. A repeated unit is a known quantity: drawn once, approved once, and produced to the same specification every time rather than resolved plot by plot.

What a developer gets from that is repeatability and certainty. The same window, to the same finish, across every elevation, with a programme that can be planned around rather than chased. It is the difference between treating timber as a luxury applied plot by plot, and treating it as a premium standard applied intelligently across the whole.

Lead times and survey scheduling

On a single plot, a lead time is a date. On a multi-plot scheme it is a sequencing problem, and it is usually what decides whether a premium specification survives contact with the programme.

Ask for the lead time from approved drawings to delivery rather than from order, because approval is where schemes lose weeks that nobody has allowed for. Ask how surveys are scheduled across plots - batched as structures reach the right stage, or taken plot by plot - and what notice your manufacturer needs to hold that sequence when the build moves.

Standardising the specification helps here too. A repeated window means one set of approvals rather than many, and a survey programme that follows the build instead of dictating it. Get both into the programme before the first plot is priced.

The value that justifies the rest

Where cost cannot come out, value goes in. Timber window lifespan runs to decades with minimal upkeep, against the shorter replacement cycle of uPVC - so the advantages of wooden windows compound over the life of the building, not just at handover. The benefits of timber windows a buyer can see and feel are part of what lets a developer command a stronger price.

Are timber windows more expensive than uPVC on day one? Usually, yes. Measured across the life of the project, and at the point of sale, the calculation looks very different.

Specify with Mumford & Wood

Our Conservation range gives developers a premium standard that scales across a scheme - box sash, spring sash and clean-lined flush casement products, all engineered for consistency across multiple plots and manufactured to meet Approved Document L and PAS 24.

Explore the Resource Centre for CAD details, performance data, BIM objects and NBS specifications covering every product in the range, book a CPD for your team, or request an estimate for a live project and test what we've said here.

Manufacturing timber windows and doors since 1954, we help developers specify a premium that works to a budget - and give your team the figures to defend the choice to the client upstream.

Frequently asked questions

Are timber windows expensive?

Not necessarily. Much of the cost sits in specification choices - bespoke sizes, complex profiles, hardwood and specialist finishes. Specified simply and consistently, premium timber windows are more accessible than developers often expect.

Are timber windows more expensive than uPVC?

Usually, yes, on day one. Timber's longer lifespan and lower replacement cost narrow the gap over the life of a building, and the saleability advantage can more than close it.

Which range should a developer specify?

Conservation. Windows in new dwellings in England have to answer Approved Document L, and PAS 24 applies under Approved Document Q. Conservation is the range manufactured to both.

How do windows affect Approved Document O compliance?

Both routes to compliance turn on the window schedule. The simplified method caps glazed area and sets a minimum free area of opening; dynamic thermal modelling gives more flexibility at a higher cost. Free area depends on how a window opens rather than on its size, so opening type and hardware need settling before the schedule is priced.

How can developers reduce the cost of timber windows?

Standardise sizes and profiles across the scheme, choose engineered softwood where a painted finish suits, keep the finish palette simple, and specify early so production and survey scheduling can be planned around your programme.

How long do timber windows last?

Well-specified, factory-finished timber windows last for decades with routine maintenance - a longer service life than typical uPVC alternatives. Our comprehensive warranties cover you up to 30 years, and can be transferred to the buyer.