What a contractor owes an architect at tender

You send a scheme to a main contractor for a tender. By then, you already know what the number needs to be. What you are actually testing is whether the contractor understands the work. More importantly, you are testing whether the contractor will protect your detail on site.

Most tender responses hand back a price and a programme. That is the minimum. What separates a contractor you can trust from one you cannot is this. It is what arrives in that tender pack alongside the number.

1. A clear bill of quantities

A bill of quantities is not decoration. It is your first evidence that the contractor has read the drawings properly. Crucially, it shows you can interrogate the proposal before anyone signs.

The bill should break down every measured item. It should list wall areas and linear metres of joinery. It should also list individual soil stacks and electrical circuits by zone. Provisional allowances should be called out separately, with their basis stated. “Unforeseen structural works” buried under a blanket contingency is not a provisional allowance. It is an excuse to add money later.

The bill should also state what is excluded. If the contractor is not supplying and fixing architectural ironmongery, it should say so. The supply chain for bespoke bronze hardware may sit with you. You may then hand over finished items for fixing. If so, the bill must separate fixing costs from the cost of the goods. This is where disputes start, and they start because the bill was vague.

You should be able to read that bill line by line. You should be able to say, “I agree with that. I disagree with that. I did not know that would cost that much”. That conversation happens before the contract, not during inspection.

2. Confirmation of the building control and party wall interface

Your scheme may carry party wall works. It may also require consultation with a planning officer after the formal application. The contractor’s tender should be clear about party wall surveyor costs. It should state whether they sit with the client or the contractor. The same for any building control liaison that goes beyond standard notification.

If the works affect a neighbouring property, the contractor should flag it. That includes a timber party wall or a flue that serves the neighbour’s boiler. The contractor should also confirm who is managing the surveyor appointment. A vague “we will agree this on site” is not good enough. You need it stated before work begins, because the dates matter. A party wall award can take four weeks from instruction to agreement. The contractor may assume you will handle it. You may assume the contractor will. Then the programme slips by a month before anyone notices.

3. A detailed method statement for critical sequences

A good tender pack includes a method statement. It covers the sequences that will kill a building if they go wrong. Basement waterproofing does not happen by accident. Taking down a party wall and rebuilding it around new beams requires planning. These are not optional things a competent contractor will just “work out on site.”

The method statement should describe how temporary support will be installed. It should say where the waterproofing membrane goes relative to the new structure. Crucially, it should show where the architect’s sign-offs fit into the sequence. A tanking inspection may happen at a particular stage. If so, the method statement should say when. Otherwise, a competent main contractor will do it when he thinks it is right. That may be after the plasterboard is already up.

This is where your detail survives or dies. Not in the specification, but in the order in which things happen on site.

4. Shop drawings, and the sign-off process

The scheme may carry bespoke joinery, cladding panels, or any item made to order. If so, the contractor’s tender should commit to a shop drawing process. It should include timescales and sign-off points.

This is not the contractor trying to be helpful. This is the contractor saying, “I understand the risk. I may cut 40 metres of walnut joinery. The dimension may be wrong by 5mm. That is because I did not submit a shop drawing for approval. If so, the joinery does not go in the building.”

The shop drawing sign-off should confirm this. The drawing will be submitted by a date you both agree beforehand. You will have a specified number of days to review and annotate. The contractor will not cut anything until the drawing carries your approval stamp. That process protects you. An architect who does not insist on it is accepting the risk. That risk is that the joinery arrives wrong.

5. Site protocols and an inspection schedule

The contractor’s tender should set out how you will access the site. It should say how inspections will be scheduled. Critically, it should state what authority you hold as the architect. You may have the right to stop work not building to the detail. If so, the contractor’s tender should acknowledge that explicitly. The contractor may believe he can proceed without your say-so. That disagreement needs to be resolved in the tender phase, not on site.

Site protocols should confirm: how the contractor’s foreman and your inspector will communicate. How defects will be logged and rectified. What constitutes “sign-off” on a completed element. It could be a site visit or a photograph reviewed off-site. It could also be a measured inspection with the architect present. Crucially, who decides whether a deviation from the drawings is acceptable or not.

These must be addressed in the tender. If not, they will become problems during the works. Problems on site cost money and time.

6. Confirmation of subcontractor appointments

Who is doing the MEP work? Is it the main contractor’s in-house team, or is it sub-let to a specialist? Is it a team the main contractor has used for 10 years? Or is it a new firm he found online a week ago?

Your tender should confirm the key sub-contracts. These include MEP design and installation. They include structural work if it is not the main contractor’s own team. They also include bespoke joinery (or at least the principal trades). And it should confirm that those sub-contracts carry the same quality standard. They should carry the same inspection protocols that bind the main contractor.

A main contractor may sub-let everything to the cheapest bidder. He may hand you a “we are not responsible for their site performance” clause. That passes the risk to you. That is fine if you are happy with it. But it should be explicit, because it changes what you are actually buying.

Why this matters

The contractor’s tender is often the only formal document of its kind. It sits between your drawings and what actually happens on site. The tender may be vague. It may answer “how much does it cost” but not “how does it build”. Then you have already lost the ability to hold the contractor to your standard.

A detailed, site-literate tender does two things. First, it tells you whether the contractor actually understands the work. Second, it gives you something to point to six months in. By then there may be a disagreement about a particular detail. The question is whether it should be built as drawn or adapted on site. The answer is almost always in the method statement the contractor already agreed to.

The tender is where your control lives. If the tender is shallow, your control ends.

If you are pricing a renovation, you want a contractor who reads the drawings. You want one who builds them as drawn. You do not want work done as they think would have been easier. Please send us the scheme or call 020 7731 6841. We will talk you through how we price work open book. We will also cover what that means for site control.