5 Estimating Mistakes Small Builders Make (And How to Fix Them)

1. Not Having a Robust Estimating Method

Flying by the seat of your pants might work in theory, but in practice, it’s a recipe for missed costs and stressed margins. Having a clear, standard process makes it much harder to forget important items.

Tip: Create an estimating checklist that covers labour, materials, disposal, overheads, and any works to existing structures. A repeatable process keeps you consistent, accurate, and far less likely to leave money on the table.

2. Not Accounting for Disposal Costs

Disposing of surplus materials or demolition waste isn’t free. A skip here, a tip fee there, and suddenly your budget has holes.

Tip: Factor in all disposal costs from the start. It may seem small, but it adds up fast and avoiding it could save your margins.

3. Ignoring Works to Existing Structures

Extensions and renovations often involve more than just the shiny new bits. Making good an old blocked-up window, repairing damaged walls, or adjusting floors may seem minor but they add cost.

Tip: Walk the site carefully, note every tweak to existing structures, and include them in your estimate. Those small items often surprise builders who didn’t plan for them. Use your above checklist to solidify this process!

4. Not Including Proper Overheads

Labour and materials are obvious, but what about the rest of running your business? Office, insurance, vehicles, softwares, admin time, pricing - all these overheads matter. Forget them, and you’re essentially working for free.

Tip: Know your overheads and build them into every quote. It’s not optional; it’s survival.

5. Skipping a “WWW” Review (What Went Well)

No builder is perfect. Every job has lessons, some good, some… not so good. Not reflecting on past work means repeating the same estimating mistakes.

Tip: After each project, take a moment to review what went well, what didn’t, and adjust your next estimate accordingly. Continuous improvement pays off more than luck ever will.

Bottom Line:

Estimating well isn’t just about numbers - it’s about awareness, experience, and learning from the past. Avoid these five mistakes, and your quotes will be tighter, your profits healthier, and your projects a lot less stressful.