I always advise my clients to obgtain competitive tenders or quotations.
If you have a builder you know from experience to be reliable and whose work is good, it may be sensible to use them without competitive tendering, especially for small jobs such as repair and maintenance work. However, for projects of any size it is reassuring to know that you are not paying "over the odds" for the work, and obtaining competitive quotes or tenders is one well-tried method of doing this.
If the work is to be funded (in whole or in part) by a grant there will almost certainly be a condition that competitive quotes or tenders are to be obtained.
If you are acting on behalf of a club, society or charity you should normally obtain competitive quotes; this demonstrates that you have not misused the funds for which you are responsible. There may well be specific rules (standing orders) setting out what you have to do.
If you seek competitive quotes or tenders:
Invite at least three and not more than six tenders - it is not fair to builders to ask too many to quote, in view of the amount of work involved in preparing a quotation. Approach the firms you intend to invite in advance and get them to confirm they are interested. Include basic information about the project; what work is required, where it is to be done and when you want them to start. Do not give any firm the identity of other firms asked to quote. If asked you can tell them how many firms have been invited to quote - this may something they consider before deciding whether they wish to quote.
Set a date for quotes to be returned. Normally allow at least two, but preferably three or four weeks for quotes to be prepared.
Issue the same information about the work required to all firms approached. Include information on the arrangements to be made for viewing the site where the work will be carried out.
If acting on behalf of a business or organisation, (club, society, charity...) tell firms that the quotes should be returned in plain envelopes marked "quotation for ....." followed by the title of the project, with no identification of the firm submitting the quotation. Keep all the envelopes unopened until the date set for submitting quotations has passed, then open them in the presence of a witness and keep a written signed record of the quotes submitted. This helps to demonstrate that you have not interfered in the tender process so as to favour any of the firms.
Write to all the firms who submitted unsuccessful quotes and include a list of prices submitted (without the names of the firms who submitted quotes). This enables firms to evaluate their competitiveness, while preserving commercial confidentiality.
and finally ...
I can do all this for you !