Phasing an Interior Over Three Years: A Worked Sequencing Example

When the budget does not cover the whole interior, the order of work matters more than the total. An illustrative calculation of what to do first and what it costs to wait.

Phasing an interior is not the same as doing less of it. Done well, it means completing everything that cannot be revisited without disturbance, then adding the elastic layers as funds allow. Done badly, it means spreading a thin specification across the whole house and then paying to open it up again. This worked example sets out a three year sequence and calculates the premium that phasing costs. Every figure is an invented assumption used to show the method, not a quotation.

The situation

An owner has completed the structure of a 350 square metre villa and has 450,000 SAR available now, with further funds expected in each of the following two years. The house needs to be habitable at the end of the first phase. The question is what to include in phase one, what can genuinely wait, and how much the decision to phase adds to the total compared with completing everything in a single programme.

Assumptions (illustrative)

• Internal area 350 square metres; six wet areas; fourteen window openings; approximately 40 square metres of majlis wall proposed for panelling.
• Funds available now: 450,000 SAR, with further amounts expected in year two and year three.
• Phase one assumed costs: wet areas at 24,000 SAR each, floors at 200 SAR per square metre, ceilings with electrical first fix at 95,000 SAR and fitted joinery at 110,000 SAR.
• Phase two assumed costs: majlis panelling at 850 SAR per square metre, decorative lighting at 28,000 SAR and window treatments at 2,600 SAR per opening.
• Phase three assumed cost: loose furniture and accessories at 160,000 SAR.
• Remobilisation and protection premium assumed at 8% on phase two work and 3% on phase three deliveries.

Step 1: Price phase one, the work that cannot be revisited

Wet areas: six at 24,000 SAR gives 144,000 SAR. Floors: 350 square metres at 200 SAR gives 70,000 SAR. Ceilings and electrical first fix: 95,000 SAR. Fitted joinery: 110,000 SAR. Phase one totals 144,000 plus 70,000 plus 95,000 plus 110,000, which is 419,000 SAR.

Every item in this phase is either concealed, structural to the interior, or impossible to add later without opening finished work. Wet areas, floors, cabling and joinery all fall into that category, which is why they take the whole of the first budget rather than being spread thinner to include something visible.

Step 2: Check what remains of the available funds

Funds of 450,000 SAR less phase one at 419,000 SAR leaves 31,000 SAR, which is about 7% of the phase one value.

That residue is a contingency rather than a budget for extras, and it is on the thin side for interior work in a building where conditions may differ from the drawings. The discipline here is to leave it untouched, because the first unforeseen condition in phase one will otherwise be paid for by downgrading something irreversible.

Step 3: Price phase two, the visible layers that can wait

Majlis panelling: 40 square metres at 850 SAR gives 34,000 SAR. Decorative lighting: 28,000 SAR. Window treatments: fourteen openings at 2,600 SAR gives 36,400 SAR. Phase two totals 34,000 plus 28,000 plus 36,400, which is 98,400 SAR.

These items are all applied to finished surfaces and can be installed without opening anything up, provided the provisions were made in phase one: a fixing substrate for the curtain tracks, a cabled position for each decorative fitting and a wall left in a condition that will accept panelling. Those provisions cost almost nothing in phase one and make phase two possible.

Step 4: Price phase three and total the phased programme

Phase three, loose furniture and accessories, is 160,000 SAR. The three phases total 419,000 plus 98,400 plus 160,000, which is 677,400 SAR.

The house is habitable from the end of phase one and complete by the end of phase three. Note that the largest single phase is the one that produces the least visible change, which is a reliable characteristic of a well-ordered interior programme and a difficult one to accept while living in it.

Step 5: Calculate the premium that phasing adds

Phase two at 98,400 SAR with an 8% remobilisation and protection premium adds 7,872 SAR. Phase three at 160,000 SAR with a 3% premium adds 4,800 SAR. The total premium is 12,672 SAR, which is about 1.9% of the 677,400 SAR programme.

Phasing is not free, but at under 2% it is remarkably cheap insurance against the alternative, which is a compromised specification in the irreversible work. The premium covers bringing trades back, protecting completed finishes while they work and the inefficiency of small separate packages.

Step 6: Test the alternative of compressing everything into the available funds

To fit everything into 450,000 SAR, the owner would need to find savings in phase one. Reducing the wet areas from 24,000 SAR to 18,000 SAR each saves 36,000 SAR, and reducing the joinery from 110,000 SAR to 80,000 SAR saves 30,000 SAR, giving 66,000 SAR.

Those savings come from precisely the two lines that cannot be revisited: the wet areas, where the hidden work determines whether the room leaks, and the joinery, where the hardware determines whether it still works in a decade. Saving 66,000 SAR there in order to avoid a 12,672 SAR phasing premium is an obviously poor trade, and seeing the two figures side by side is what makes it obvious.

What changes the answer

• If the provisions for phase two are omitted in phase one, for example the curtain track substrate or the cabling for decorative fittings, the phase two premium rises sharply because finished work must be opened.
• If prices move between phases, the later phases cost more than modelled, and the premium calculated here understates the real cost of waiting.
• If the household occupies the house during phase two, protection and working hours become more restrictive and the premium rises.
• If a phase two item becomes unavailable, a substitution may not match what was installed in phase one, which is an argument for buying matching materials early even if installing later.
• If the value added tax treatment differs between phases or between supply and install arrangements, the totals shift, so confirm the position against the published headline rate of 15% with ZATCA for each contract.

What the numbers tell you

• Phase by reversibility: complete everything concealed or hard to revisit first, and leave the applied layers for later.
• Make the provisions for later phases during the first phase, since substrates, cabling and fixings cost almost nothing early and a great deal later.
• The premium for phasing is usually small relative to the cost of compromising the irreversible work.
• Expect the largest phase to produce the least visible change, and plan for that expectation within the household.
• Rules, prices and requirements change over time, so confirm current costs, tax treatment and any approval requirements with your suppliers, ZATCA and the relevant authority at the time of each phase, and take contractual or tax questions to a licensed adviser rather than relying on an illustrative model.

Limits of this example

Every figure above is an illustrative assumption used to show the method, not a quote, valuation or market rate. Costs, rates, fees and regulations change and must be confirmed with the relevant authority, lender or supplier before you commit.

Domira designs and delivers interiors as part of the building, not after it: the finishing schedule, the joinery and the services coordination that decide whether a space looks built or assembled. Share the space and Domira will tell you what it would specify and what it would leave out.