Here are the 10 most common reasons why designers get sued. Some are common sense; others constitute large pits concealed in the contractual undergrowth

Designers are increasingly at the centre of construction industry disputes. Here are the 10 most common reasons why they find themselves there, along with some advice on how to keep out of the firing line.

1 Standard of care

Designers are required to work to the standard of an ordinary competent person exercising and professing to have their particular skills. However, just doing what everyone else does may not be sufficient. Each situation should be considered

on its merits and, if the generally accepted practice is not appropriate, further steps should be taken. Beware if you profess to have a specialism in a certain area, as you will be judged against others with this specialism rather than a person of ordinary competence.

2 Practicality of design

A design can be found negligent if it lacks "buildability" or "supervisability". Designers must take into account the conditions in which work is to be carried out. They must ensure that it can be done by those likely to be employed and consider how it is to be inspected.

3 Reconsideration of design

If the design remit extends into the construction phase, the designer has a continuing duty to consider it and correct any errors that emerge. Difficulties encountered in carrying out work in accordance with the design cannot be ignored.

4 Untried methods

The client should be warned and give express approval if untried materials or work methods are being used. Otherwise, if there is a failure, it will not be sufficient to say the design was "state of the art".

5 Fitness for purpose

Even if not expressly stated in the contract, an obligation for the design to be fit for purpose can be implied if the purpose is made known to the designer, or if the employer relied on the designer's expertise. A designer can only be sure of avoiding this onerous obligation if the contract expressly excludes it.

6 Duty to warn

If part of a project requires specialist knowledge you do not have, you are obliged to inform the client and advise it to take other advice

Contractors must warn designers if they know or believe there are defects in a design. Where there are health and safety implications, contractors who do not receive a response have a duty to escalate objections in an increasingly formal and insistent manner, by putting them in writing, approaching higher levels of management and, ultimately, either reporting them to regulatory authorities or suspending work.

7 Scope of duty

Beware of advising, even informally, on matters outside your knowledge. If part of a project covered by your design contract requires specialist knowledge that you do not have, you are obliged to inform the client of this and advise

it to take other advice. You must state expressly, in writing, any limitations to your own role. However, even if specialists are then brought in, your obligations remain for any aspect of the work of which a designer of ordinary competence ought to be aware, despite anything that specialist says or does.

8 Specialist client

A designer's duties are not reduced in any way even if the client has specialist knowledge or skills that might assist understanding of the design.

A client has no duty to examine the design and tell the designer if something is wrong.

9 Liability for design by others

A designer taking over a project for which a partial design or preliminary design information is already in place is responsible for completing

it unless there are contractual terms to the contrary. "Completion" is taken to include understanding the principles underlying the work carried out and forming a view on its sufficiency. The designer is assumed to have agreed to prepare the entire end result with reasonable skill and care, no matter how much of the work was done by others.

10 Duty of care to other parties

A designer making a design representation intended to be seen and relied on by others, such as prospective purchasers or lenders, is taken to have assumed responsibility to these people too. Designers must take reasonable care to ensure that representations are reliable and the underlying design work has also been prepared with reasonable care.