Builder Markup on Materials: Should You Buy Them Yourself?
Builder markup on materials is typically 10–20% on supply and fit. Buying your own can cost more than it saves: on a 5% VAT job you lose the relief entirely.
Should you buy your own materials to avoid builder markup?
Usually not, and on some jobs the maths is settled before you look at a single price. A builder's markup on materials sits at roughly 10–20% on a normal domestic supply-and-fit job, which is the gap you would need to beat at retail against their delivered trade price. But the decisive number is VAT, not markup. HMRC's VAT Notice 708 states at section 2.2 that "Builders charge VAT on building materials that they supply and incorporate in a building (or its site) at the same rate as for their work." The reduced and zero rates attach to materials only when the builder supplies them. Buy the same goods yourself and they come back at 20% over the counter.
On a standard-rated job that changes nothing, because it is 20% either way. On a job that qualifies for 5% or 0%, self-supply hands back 15 to 20 percentage points before a single point of markup is discussed. That is the part of this decision most homeowners never see, and it is the part your builder often will not raise, because they assume you already know your rate.
The VAT rate decides it before markup does
Most people ask about markup because a quote came in over budget and the material line looked large. Fair enough. But work out your VAT rate first, because on three common job types the answer is fixed.
| Job type | VAT on materials the builder supplies | VAT on materials you buy |
|---|---|---|
| Extension, refurbishment or repair to an occupied home | 20% | 20% |
| Renovating a home empty for 2+ years | 5% | 20%, not recoverable |
| Converting a non-residential building into a dwelling | 5% | 20%, may be recoverable |
| Building a new dwelling | 0% | 20%, may be recoverable |
| Installing energy-saving materials (to 31 March 2027) | 0% | 20%, not recoverable |
Two of those rows carry a caveat worth understanding. On a genuine self-build or a qualifying conversion you can reclaim VAT on materials you bought yourself through the DIY Housebuilders' Scheme, which is why self-builders routinely buy their own materials and engage trades on a labour-only basis. It is a cashflow cost and a paperwork job with a hard deadline, but the money comes back.
The empty-property row has almost no such escape. If a house has been unoccupied for at least two years, qualifying renovation work is charged at 5% when the builder supplies the materials, and there is no DIY reclaim route on a two-year empty. There is one exception further up the timeline: a dwelling not lived in for ten years or more is treated as non-residential, so bringing it back into use counts as a conversion rather than a renovation, and a DIY Housebuilders' Scheme claim becomes possible. Between two and ten years empty you are on the 5% rate with no reclaim, and every pound of material you buy yourself on that job is a pound taxed at 20% instead of 5%.
The energy-saving materials row is the sharpest of the lot. Installation of specified energy-saving materials in residential accommodation is zero-rated until 31 March 2027, after which it reverts to 5%. The relief attaches to the installation. The guidance is explicit that supply without installation is standard-rated, so a retailer selling you loft insulation charges 20% and always has. Buying your own insulation, then paying someone to fit it, converts a zero-rated package into a 20% purchase plus labour.
Builders charge VAT on building materials they supply and incorporate in a building at the same rate as their work, and the notice adds that some items are not building materials and remain standard-rated. Carpets and fitted bedroom furniture are the usual examples, and a builder must charge 20% on those even on a 5% job. That is why the 5% and zero rates cover qualifying materials at all: they follow the service. Materials you buy over the counter are a separate retail supply to you, and retail is standard-rated at 20%. Check which rate your job attracts before you decide who buys what.
Our full guide to VAT on building work covers how to establish which rate applies and what evidence a builder needs to charge 5% properly.
Here is the arithmetic on a 5% job
Take a £6,000 package of qualifying building materials on a renovation of a property empty for over two years. Numbers are illustrative, but the structure is what matters.
| Builder supplies | You supply | |
|---|---|---|
| Material cost | £6,000 trade, delivered, before VAT | £6,600 retail, delivered, before VAT |
| Markup at 15% | £900 | none |
| Net | £6,900 | £6,600 |
| VAT | £345 at 5% | £1,320 at 20% |
| You pay | £7,245 | £7,920 |
Both material figures are shown before VAT so the tax lines compare like for like. A retail price on a website will normally already include the 20%.
You have paid £675 more, taken on the ordering, storage and returns, and given up any single point of responsibility if a product turns out to be wrong. The markup you set out to remove was £900. The VAT swing was £975. That is the whole argument in one table.
Run the same numbers on a standard-rated 20% job and it flips to an honest question rather than a settled one: the builder route is £6,900 plus £1,380 VAT, or £8,280, and your route is £6,600 plus £1,320 VAT, or £7,920. A real saving of £360, about 4% off the total, in exchange for doing the work yourself. Whether that is worth it depends entirely on how good your retail price actually is.
What the markup is paying for
Trade discounts are real, but they are not a fixed number and nobody should quote you one. They vary by merchant, by the size of the account, by product category and by how much the builder spends in a year, and merchant list price is largely notional anyway, so "percent off list" tells you almost nothing. The only comparison that means anything is the delivered price your builder can actually get against the delivered price you can actually get, for the same specified product.
What sits on top of that price is handling, and handling is close to a fixed cost per line rather than a percentage:
- Ordering and specification. Getting the right lintel, the right tile trim, the right quantity of adhesive for that substrate.
- Delivery scheduling. Materials landing when the trade is on site, not three weeks early on your drive.
- Storage and security. Somewhere dry and lockable for plasterboard, timber and a boiler.
- Waste and over-order. Tiles at 10% extra for cuts and breakages, timber cut to length, brick and block ordered in whole packs.
- Damaged or wrong deliveries. The merchant's collection, the replacement, and the lost day.
- Cashflow. Materials paid for before your next stage payment lands.
That is why a percentage argument on its own goes nowhere. Look at the pounds:
| Material line | Markup at 10% | Markup at 20% | Markup at 30% |
|---|---|---|---|
| £120 waste and trap kit | £12 | £24 | £36 |
| £900 bathroom suite | £90 | £180 | £270 |
| £2,500 kitchen units | £250 | £500 | £750 |
| £6,000 windows and doors | £600 | £1,200 | £1,800 |
| £20,000 full material package | £2,000 | £4,000 | £6,000 |
Thirty per cent on a £120 fitting is £36, which does not cover the trip to the merchant. Thirty per cent on a £20,000 package is £6,000, and nothing on the handling list above scales to that figure. Small items justify a higher percentage; large packages do not. Our guide to signs your builder is overcharging works through what a genuinely inflated material line looks like when you price the products yourself.
Where self-supply genuinely makes sense
There are real cases, and they share a shape: standard-rated work, a small number of high-value items, and a specification you can pin down exactly.
- One expensive, easily specified item. A bathroom suite, a kitchen, floor tiles, a wood-burning stove, sanitaryware. Online discounting on branded goods can beat merchant trade pricing, and the product code makes the comparison honest.
- You already have a trade route. A relative in the trade, a merchant account through work, a genuine discount you can evidence.
- Labour-only or day-rate arrangements. If you are already paying day rates rather than a fixed price, materials were always going to be handled separately, so agree the basis up front.
- Self-build and conversion. Where the DIY Housebuilders' Scheme is available, the VAT objection falls away and buying your own becomes a mainstream approach.
The cases where it rarely works are the mirror image: bulk structural materials, anything measured off a drawing, anything with a lead time, and anything where getting the quantity wrong stops the job.
What you give up, and what you keep
The common claim is that supplying your own materials "voids the warranty". That is not right, and it matters.
Section 49 treats every contract to supply a service as including a term that the trader must perform the service with reasonable care and skill. Section 57 says a contract term is not binding on you to the extent it would exclude that liability. So a builder who fits your materials badly is still answerable for the fitting, whoever bought the goods, and cannot write that duty out of the contract.
What does change is your route on the goods. When the builder supplies the materials, your rights over the product itself run against the builder as well as the workmanship, so one person answers for the whole outcome. When you supply them, your claim over a faulty or misdescribed product runs against the retailer who sold it, plus any manufacturer warranty, while the fitting stays with the builder.
That split is the real cost, and it is not a legal loss so much as a practical one. If a shower tray leaks, the builder can point at the tray and the retailer can point at the installation, and you are the only party contractually connected to both. On a job with a defect that is genuinely ambiguous, that is an expensive place to stand. Our guide to consumer rights in building disputes covers how those claims actually run.
Many builders will also decline to fit customer-supplied goods, or will price the labour higher to cover the risk, or will exclude the product from any voluntary guarantee they offer on top of your statutory rights. All three are legitimate. Raise it before the quote is priced, not after.
What goes wrong
You compare retail against trade and call the gap markup. A quote showing "supply and fit bathroom: £4,200" is not claiming the suite costs £4,200. Ask for the material schedule with product names and codes, then price those exact products delivered. Comparing a builder's all-in figure to a website price with no labour and no delivery produces a markup number that is pure fiction.
You under-order and the second delivery eats the saving. Tiles from a different batch, a part-pack of blocks, a delivery charge on £80 of timber, and a day of standing time for two trades. Merchants price small top-up orders badly on purpose. This is the single most common way a self-supply saving disappears.
You lose the 5% rate without knowing the job qualified. Nobody tells you the property's two-year empty status changes your VAT rate on materials, because the builder assumes you know and you assume it is their problem. On a £30,000 renovation with £12,000 of materials, that is around £1,800 of avoidable tax.
The scope goes vague at the boundary. Once materials are split between two parties, "supply and fit" becomes "fit only, materials by client" for some lines and not others. That ambiguity is where variations breed. Check the quote actually says which side of the line each item sits on, using our list of what a builder's quote should include.
You buy the wrong specification and it fails Building Control. Insulation with the wrong thermal conductivity, a lintel with the wrong load rating, cable of the wrong size. The builder can refuse to fit it, and rightly so. If a material is specified on a drawing or in a Building Control submission, let the person answering to the inspector buy it.
How to test this on your own quote
Ask for the material schedule as a separate list with product names, codes and quantities. Then do three things: establish your VAT rate, price two or three of the highest-value lines delivered from a real retailer, and compare the total against the quote's material figure less the labour. If the builder will not itemise the materials at all, that refusal is the finding.
If the gap between your retail pricing and the quote sits inside 10–20% on a large package, that is normal and you are looking at a fair quote. If it sits above 30% on a large package of goods you can buy off a shelf, ask the question directly and see whether the number moves. On small-value lines a higher percentage is normal, because the handling cost is close to fixed per line rather than proportional. And before you decide to buy anything yourself, check whether your job is standard-rated, because on a 5% or zero-rated job you are usually arguing yourself into a worse price.
Where a quote lumps materials into a single unexplained figure, that is often a provisional sum in disguise, which is a different problem with a different fix. And if you are still working out how the material and labour lines relate to each other at all, start with how to read a builder's quote.
Check the material line on your quote
The material figure is the easiest line in a quote to inflate and the hardest for a homeowner to sanity-check, because it is usually the only line with no unit rate attached. Upload your quote and we check whether the materials are specified at all or hidden in a lump sum, benchmark the price against real UK costs for the work described, and flag where the material line is doing work the rest of the quote cannot explain. It usually takes about ten minutes.
Got a supply-and-fit quote? Check what the material line is really marked up by
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Get my estimateSources
- HMRC: Buildings and construction (VAT Notice 708) - section 2.2 on the VAT rate applied to builder-supplied materials
- HMRC: VAT on energy-saving materials and heating equipment (Notice 708/6) - the zero rate to 31 March 2027 and why supply-only is standard-rated
- HMRC: DIY Housebuilders' Scheme eligibility - which projects allow a reclaim on self-bought materials
- Consumer Rights Act 2015, section 49 - the duty to perform a service with reasonable care and skill
- Consumer Rights Act 2015, section 57 - liability under section 49 cannot be excluded
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