Who keeps leftover building materials after a relatively small job is completed?

[SoftBoiled]

My builder has bought trade quantities of materials for a relatively small job and presented me with an invoice. There'll be loads leftover. Does he get to take the stuff when the job is done or am I stuck with it or can I offer it to him in return for a reduction on the final bill, effectively selling it back to him if he should happen to need / want it? What's the done thing?

Sounds like a bit of a scam if he is expecting to take the surplus that you have paid for away but you probably don’t want to be left with stuff to store. I would be straight with him “the quantities you have ordered seem to be a lot more than this job requires. Will you buy back what is left afterwards or do I need to sell it elsewhere?”. Make it clear you won’t be taken for a mug.

question the amount he's ordered.and compare it with the estimate.

If it's something like Karndean they are bought by the pack so there can be quite a lot of waste, but you should get to keep it. Our joiner always leaves us the leftover door handles he orders in our fixed price contracts though I imagine you are talking about bigger amounts.

Whoever pays for them keeps them.

If you paid for the job, then he does, if you paid for labour and materials then you do.

But you should ask the question to him

Thank you, that's really helpful.

There isn’t one universal rule, so I’d get this agreed before the work starts rather than relying on “what’s normally done”. If you’re being charged for the materials, ask for the quote/invoice to say whether the unused items become yours or are being returned/credited. On a fixed-price job, the builder may have allowed for normal waste and trade pack sizes; on a materials-at-cost arrangement, the unused balance would normally be yours unless you agree otherwise.

I’d ask for a list of what he has ordered, why the quantities are needed, and what can be returned for a refund. Keep unopened, returnable items until the job is signed off, and agree any credit at the actual net cost rather than an informal “buy-back”. For items bought specifically for your job, it’s reasonable to ask for them to be left with you; for leftover sand, boards, fixings etc. that he can use elsewhere, agree a clear credit or let him take them. Put the agreement in a text or email so there’s no awkwardness at the end.