The Epsom Extension That Went Over Budget and the One Decision That Caused It

 

We went over budget by fourteen thousand pounds. On a project that was supposed to cost fifty five thousand, that is a significant overrun. Nearly twenty five percent more than we planned for.

The extension itself is lovely. Single storey rear. Open plan kitchen diner that connects beautifully to the garden. Rooflight that floods the room with natural light. Everything we wanted.

But fourteen thousand over. That money came from our savings. From the holiday we cancelled. From the new car we postponed. From the landscaping budget that got slashed so the garden still looks like a building site six months after the builder left.

One decision caused almost all of that overrun. And it happened before the builder was even appointed.

If you are planning an extension in Epsom and looking for an architect epsom who will help you avoid the mistake we made, heres what went wrong and why.

The Decision That Cost Us Fourteen Thousand

We skipped the detailed drawings.

Our first architect produced concept designs and planning drawings. Nice floor plans. Elevations that looked good. Enough to get planning approval from Epsom and Ewell Borough Council. Which we did. Eight weeks. No problems.

But the planning drawings were not construction drawings. They showed the shape of the rooms and the position of the windows. They did not show foundation details, steel specifications, insulation build ups, drainage connections, floor construction, or material specifications.

We sent these planning drawings to three builders for quotes. The builders did their best. But they were pricing incomplete information. Each one made different assumptions about things the drawings didnt specify.

The cheapest quote made the most assumptions. Shallow foundations. Standard insulation. Basic drainage connection. Provisional sums for things that should have been specified precisely.

When construction started, reality hit. The foundations needed to be deeper because of clay soil and a tree near the boundary. The insulation needed upgrading because the planning drawings didnt specify a value and building control required better than the builder assumed. The drainage connection was more complex than expected because a shared drain ran closer to the house than anyone checked.

Each discovery triggered a variation. Each variation added cost. Five hundred here. Fifteen hundred there. Two thousand for the deeper foundations. Twelve hundred for the insulation upgrade. By the end, fourteen thousand in extras that were never in the original quote because the information was never in the original drawings.

What Detailed Drawings Would Have Changed

Everything.

A proper set of building regulations drawings would have included the structural engineers foundation design based on actual soil conditions and tree proximity. The builder would have priced the correct depth from day one. No surprise. No variation. No extra cost.

The insulation specification would have been calculated and stated on the drawings. Every builder would have priced the same U values. No assumption. No building control issue. No upgrade cost.

The drainage layout would have been designed based on Thames Water records showing where the existing drains run. The connection route would have been planned. The builder would have priced the actual work required. No discovery. No variation.

Detailed drawings cost more than planning drawings. Our architect quoted an additional three thousand for the full building regulations package. We decided to save that three thousand and let the builder figure it out.

That three thousand saving cost us fourteen thousand in extras. The maths speaks for itself.

Why This Happens More Than People Realise

Most homeowners dont understand the difference between planning drawings and construction drawings. They see a set of plans that got approved by the council and assume those plans contain everything the builder needs.

They dont. Planning drawings show the council what you want to build. Construction drawings show the builder how to build it. They are different documents with different purposes and different levels of detail.

Some architects produce both as part of their standard service. Others charge separately for each stage. And some architects only produce planning drawings and leave the technical side to others.

Ask your architect specifically what is included in their fee. Does it cover building regulations drawings. Does it include structural engineering coordination. Does it include a detailed specification that builders can price accurately.

If the answer is no, budget for it separately. Because the cost of not having detailed drawings is always more than the cost of producing them.

The Builder Is Not the Problem

Our builder was good. Experienced. Professional. He built exactly what was in front of him. When the drawings didnt specify something, he made a reasonable assumption. When that assumption turned out to be wrong, he charged for the change.

That is not the builders fault. That is the fault of the information he was given to work from.

Blaming the builder for extras caused by incomplete drawings is like blaming a taxi driver for getting lost because you gave them the wrong address. The input determines the output. Better drawings in means fewer surprises out.

What We Tell Everyone Now

Spend the money on detailed drawings. Every penny of it. The three thousand we tried to save cost us fourteen thousand in the end. That is not an unusual ratio. We have spoken to other homeowners in Epsom who had similar experiences. The savings on skipping detailed drawings are always dwarfed by the costs of the problems they would have prevented.

Six to eight months from first conversation to completion. Budget for the full architectural service including building regulations drawings and structural engineering. Get three builder quotes based on complete information. Compare like for like. And never send planning drawings to a builder and ask them to price from those alone.

That is the lesson. Expensive for us. Free for you.