Bid ≤ target price
Direct client approval. It is awarded and certified against invoice.
A contracting position, not a calculator
One-off projects · visible fee · Málaga
Open-book budgets
Madercon takes one-off work —house, structure, roof, a development with character— from a €20,000 job. The client sees invoices and the fee. We do not compete to be the cheapest opaque figure.
An open-book contract (actual cost plus fee) puts economic control on admissible cost. A lump-sum fixes a figure from day one and loads the risk — and the premium — onto the builder. Below a €20,000 job, this is not the product: it is a bounded workshop job, or it does not come in.
Updated September 2026
Open-book versus lump-sum
Two ways to contract the same job. The difference is not the material: it is who sees the margin and who pays the unforeseen.
| Criterion | Open-book (cost-plus) | Lump-sum (turnkey) |
|---|---|---|
| Transparency | Access to invoices, subcontractor quotes and trade breakdown. The fee sits apart. | The client sees the trade total, not the real margin. |
| Changes of quality or supplier | Qualities and suppliers can move without a penalty for the change itself. | Any change on the original project becomes a variation at a premium. |
| Financial risk | If supplies rise or something unforeseen appears, cost moves. A guaranteed maximum (GMP) caps the ceiling when the project is measured. | The builder takes market swings — and charges for them up front as a premium. |
| Opening cost | Usually lower: there is no inflated risk premium in every chapter. | Usually includes a markup to cover contingencies that may never happen. |
| Programme | More variable if suppliers change mid-job. The programme is agreed by milestones. | Stricter. Delay damages, if agreed, sit in the original contract. |
Open-book (cost-plus). Open-book avoids paying the lump-sum risk premium. Purchases can be decided as the job runs, and trades can be fitted to real liquidity. It asks for attention: bids have to be validated. If the project is poorly defined or supplies rise, the out-turn moves — unless there is a GMP.
Lump-sum (turnkey). Lump-sum gives a figure on day one. It fits if a development mortgage or a lender demands a locked total. The risk is incomplete trades: anything not spelled out is charged dear. The client does not see the margin and cannot bring a trade without a fight.
How Madercon contracts
Open-book with target prices. Visible fee. Cap per trade. Client contribution where law and insurance allow.
- Admissible-cost ledger. Material and subcontract invoices in view. The management fee is charged apart, agreed in the contract, not buried in the timber rate.
- Target costs. An acceptable ceiling per chapter is set before tender. If a subcontract exceeds it, it is justified or an alternative is found. This is not guessing the exact cost: it is marking the maximum before buying.
- Guaranteed maximum (GMP) when measured. If the execution project is measured, a global ceiling can be agreed. Below it, the saving is visible. Above it, the excess has to be argued — it is not swallowed in silence.
- Payment on certified milestone. Work done is certified. If the job stops, completed work and that phase's fee are settled. It is not “the client forfeits everything paid”: it is settlement of what was built.
Where reference prices come from
Three sources, none of them a live engine on this site. The schedule is closed at tender, with the project on the table.
- Construction price databases. CYPE / Price Generator, BEDEC (ITeC) and regional databases. They break down labour and material per unit. They are a trade ceiling, not Madercon’s public rate card.
- The architect’s bill of quantities. The execution project carries a bill of quantities. We ask for updated market rates, not only the minima stamped by the professional body.
- Two or three local bids on the heavy trades. Before signing with the main contractor, informative bids can be asked of structure, external joinery or climate trades. That anchors the target price.
Target-cost schedule
A typical annex to the open-book contract. If the subcontract exceeds the figure, it must be justified or another trade found.
Illustrative example for a typical house. It is not a Madercon quote and not a current rate card.
| Trade / chapter | Unit | Qty | Target rate | Estimated max. |
|---|---|---|---|---|
| Foundations and timber structure | m² GFA | 220 | €180.00 | €39,600 |
| Sheltered roof / insulation | m² | 150 | €75.00 | €11,250 |
| External joinery | m² | 50 | €320.00 | €16,000 |
| Climate (heat pump) | item | 1 | €18,500 | €18,500 |
| Finishes — supply | m² | 180 | €28.00 | €5,040 |
| Example total | €90,390 | |||
Price approval during the works
The ceiling is set in the contract. The purchase is decided with three bids on the table, not in a late WhatsApp.
- The client sets the target price of each chapter in the contract (specification + reference schedule).
- Madercon tenders that trade to three subcontractors, on the same quantities and the same qualities.
Bid > target price
Madercon argues the excess. The client may:
- Accept the overrun, in writing.
- Adjust qualities or the scope of the trade.
- Bring their own subcontract that meets quantities, H&S and programme.
Client contribution
If there is a trusted trade, material already bought, or a wish to paint, it can be integrated. The fee covers coordination, not a markup on what you supply.
Stays with Madercon
- Structure, foundations and any trade that affects the ten-year insurance.
- Façade, roof, weathertightness and envelope insulation.
- Installations that need an official certificate: gas, high voltage, certified climate.
- Site H&S and coordination of trades on the plot.
The client may supply
- Supply of sanitary ware, taps, floors, lighting or kitchen.
- Interior paint and timber doors or wardrobes.
- Planting, light fences and non-structural pergolas.
- Fitting of extra-low-voltage accessories, with wiring already in.
If client material is late and stops the crew, the contract may set a standing rate. After a stated delay, Madercon may buy and fit the equivalent and add it to the open book.
Limits — what this page is not
- Not a price engine. There is no CYPE or BEDEC API behind this site. Nor a wizard that computes a monthly instalment. The schedule is written with the project, not a form.
- We are not a bank or a valuer. We do not offer a mortgage, we do not query credit files, we do not register charges. Finance, if studied, is case-by-case accompaniment.
- No DIY on structure. If the client builds structure or envelope, the technical control body may issue a reservation and ten-year insurance drops. That blocks a mortgage and a sale for ten years. Those trades are not marked as client-supplied.
Frequently asked questions
What is an open-book budget?
A contract of actual cost plus a management fee. You see the invoices. We do not earn by hiding margin in the material.
Can I still ask for a lump-sum?
Yes, when the project is defined and a lender demands a locked figure. Then the risk — and the premium — sit in the price.
Do I have to check every invoice?
Trade bids have to be validated. It is not a contract for someone who wants to ignore the money. If there is no time, lump-sum fits better.
Can I bring my plumber or my tiles?
On non-structural trades, yes: quantities, H&S and programme are coordinated. The fee does not inflate because the material is yours.
What if I want to erect the roof myself?
No. Roof, structure and envelope stay with the builder. Ten-year insurance and technical control are not negotiable on that line.
Does this site calculate the price of the house?
No. The schedule on this page is a format example. The real budget comes from the project, the quantities and three bids.
Do you finance the works?
No. We do not finance. Payment is by milestone. If you need a bank, it is yours. Finance.
Ask for a target-cost schedule
Town, use, area or span, and whether an execution project already exists. We reply in workshop hours.
How it is paid
Madercon does not finance. There is no credit or deferral on this site. The contract is paid on certified milestone. If a bank is needed, it is yours: we accompany with the project and the certificates.
We do not offer finance
- Payment by milestone. Work done is certified and that phase is paid. That is the contract, not a loan.
- If a bank is needed. A mortgage or other credit: the lender is yours. We do not lend and we do not publish instalments.
The actual case is talked through in contact. From a €20,000 job. The technical study comes first.