House Design Masterclass Part 6: Tender Pack

Architect Julian Owen explains how to present these essential documents to any prospective construction workers
Build It expert Julian Owen
by Julian Owen
26th October 2019

For lots of self builders, this is the time to let loose a passion for interior design and set out
on the biggest and best shopping experience ever.

There are many choices to be made using the wealth of ideas to be found in magazines, on TV, on the internet and at the specialist shows such as Build It Live.

The architect is there to prompt and advise on the options and then turn it all into a package of drawings and specifications with the aim of getting the most cost-effective price from a builder.

Crucially, enough information must be assembled to enable each tendering contractor to calculate a reliable quote.

part 5: Building Regulations

As explained in the ‘Design Series Part 5’, the fitting out of the structure goes beyond anything that is of interest to the building inspector. For example, as long as a washbasin is correctly connected to the drains and water supply it will be approved by the building control officer.

But the appearance and quality of the sink along with details such as the choice of taps and plugs will probably be important to you, as well as the cost. The same principle applies to many other aspects, too, such as exact choice of bricks, window type and a myriad of finishes and fixtures.

A typical tender package for a new house consists of 1:50 scale plans and elevations, at least one 1:20 section (often several), electrical layouts, a plan of the drainage and the services, a set of larger scale details and a specification of the building work.

A large 1:20 scale section takes time to prepare but it allows the architects to identify and resolve problems which would otherwise have to be worked out by the builder during construction. For a typical house it’s realistic to expect the contractors to work out the amount of materials needed themselves, but for larger projects, it’s essential to include a bill of quantities.

Budgets and finance for project managing self-builds and renovations

This is usually prepared by a quantity surveyor working alongside the architect and lists the exact amounts and types of all the materials required.

It takes skill and experience to judge the right level of information to be sent out for pricing. Too many drawings and documents can cause as much of a problem as too few, but there is no doubt that skimping on the level of detail in the tender package is one of the main causes of contractual disputes between builders and their clients.

If there are gaps in the specification or design features that are not adequately explained, whoever is preparing the tender will assume that you want them to use the cheapest possible option. Who can blame them when the lowest price will probably win the work?

Avoiding an ambiguous plan

If an item has been missed or the quality does not match what you intended, this can lead to extras being demanded during construction.

The tender package has to describe the work to a sufficient level of detail to get a reliable fixed price covering the aspects of the design that you consider important.

If you are not concerned about the exact description of an item, you can harness the negotiating skill of the contractor to get the best possible price.

For example, the concrete blocks must have sufficient strength and a certain level of insulation, but you probably won’t mind who makes them, so it is best left to the builders to use the cheapest supplier they can find.

Sometimes it is difficult to define certain aspects of the quality of the workmanship you are looking for with a great deal of precision. Paintwork or joinery that might be acceptable to one person may be considered a bodge by another.

This conundrum is best dealt with by ensuring the builders chosen to tender are all known to work to a similar quality – and your designer may be able to help with this.

The technical design of electrics, heating and plumbing requires specialist knowledge that is beyond the typical skillset of an architect if the arrangement of the services is complex you will benefit from the advice of a consultant.

But for most home building projects, a performance specification is sufficient, which is a simple description of what the services have to do and where they are to go.

In the case of the electrics, this might be plans showing all the plugs, sockets, switches and types of light. The heating system specification might require particular suppliers to be used, indicate approximate radiator positions and set target temperatures that must be achieved inside the house during the winter months. Circuit diagrams, pipe runs, thermal calculations and radiators are later worked out by the contractor’s team.

Getting the technicalities right

Writing a specification needs someone with sound technical knowledge and the ability to take an imaginary walk around the house in their mind’s eye to make sure that all the important features are included. The finished document has to be comprehensive, logically organised, written in plain English and, most of all, unambiguous.

If there are items that you cannot finalise before work starts, or you wish to nominate your own subcontractors, then the watchword is ‘clarity’.

planning costs for a build

The estimators working out the tender prices need to know exactly who will be doing what, with no grey areas. You might have chosen your kitchen supplier, but who will provide the wiring and plumbing connections, or the tiling between the worktop and cupboards? Will you employ the kitchen fitters directly yourself or do you want the main contractor to take them on?

Provisional sums and prime cost sums are terms used in the building industry to describe work that is to be included in the contractor’s price but has not yet been defined when the tender pack is sent out – typically for the sanitaryware or tiling.

If possible, they should be avoided, as they’re not binding. They’re often used in commercial schemes where preparation time is short and the contract price is to be formally approved by a board of directors.

For a self build project, it is better to note down the likely cost and exclude the work from the tender package. Typically this can be done with sentences such as “client to supply sanitaryware, contractor to fit and provide all necessary connections and builder’s work”.

Once a builder is on board, they can be given the opportunity to price for the extra work without being tempted to spend up to your budget figure unnecessarily.

How detailed should a tender pack be?

Although a tender package should cover all the important aspects of the work, there is a danger in providing too much information. I have seen tenders for self builds that have been prepared by architects who are more used to large commercial projects.

They send contractors piles of weighty documents with screeds of completely standard workmanship and specification clauses, along with many sheets of equally standard construction details.

Self-Build Zone builders examining plans

I suspect these are an attempt to impress their clients with how much work they have done. In my opinion this approach can be counterproductive for relatively modest one-off houses because the package is likely to end up on the desk of an overworked local builder who prepares tenders in the evenings and weekends and has to work quickly and efficiently.

Even if they are not completely put off by an extensive pile of paperwork, they will not have time to read it all and they might assume that they are dealing with a particularly exacting potential client. From their point of view, this increases their risk of under-pricing the job, so a sensible precaution is for them to add a healthy extra contingency onto the estimate to cover it.

Shortcuts to setting standards

It is possible to reduce the paperwork sent to tenderers whilst ensuring that a good build and finish quality is included in the quoted price. One way is to state that the building standards of respected sources that are familiar to most contractors must be followed.

For example, The National House Building Council (NHBC) publishes a book which covers most of the important aspects of the construction of a dwelling, well beyond the minimum rules set by the Building Regulations.

Similarly, there are British Standards documents that describe good practice for aspects of building work. The Timber Research and Development Association (TRADA) produces a host of excellent, well-illustrated publications filled with useful drawings and specifications.

Both of these sets of standards can be incorporated into the specification using the following: “Unless otherwise stated, all work is to comply with current NHBC Standards and TRADA recommendations for good practice”.

There are some other phrases that can act as a safety net to make certain everything is included in the tender price, such as “the contractor is to ensure all work must be in accordance with the current Building Regulations”.

This is an automatic legal requirement, but it’s worth stating in writing in case the builder later tries to charge extra for work that has not been expressly described anywhere.

Another useful caveat to add is “The contractor is to price for all work that is reasonably apparent as being necessary to complete the project regardless of whether or not it is described in this document”.

This is again simply stating the contractual position but I added it to my own standard document long ago following a surreal argument with a builder. He tried to charge extra for plasterboard on the ceilings because although it was clearly shown on the drawings it was not mentioned in the specification.

He threatened to leave the ceiling joists bare unless he was paid extra to board them and only gave in when I asked how he was going to fix the lights, paint the ceiling and complete the house without it.

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