Example report — illustrative figures, not a real quote.Get your own — £1.99

Sample estimate · dormer loft conversion with 1 Bedroom, 1 Bathroom / En-suite

Your Loft Conversion Budget Estimate: A Clear Guide

This report provides an estimated budget for your dormer loft conversion. It helps you plan your finances. Remember, this is not a builder's quote. Actual quotes often include more detail and may be higher.

Costs adjusted +30% for SW1A area (BCIS regional factor)~8 weeks on site396 labour hrs3 things to be aware of ↓

Total cost estimate

Low

£58,291

inc. VAT

Mid

£64,768

inc. VAT

High

£77,721

inc. VAT

Your estimated total cost, including VAT, could range from £58,291 to £77,721. The mid-point estimate is £64,768 before VAT, and £77,721 including VAT.

Build cost£36,836

Contingency (12%)£4,420

Overhead (12%)£6,371

Profit margin (10%)£5,309

Site costs & fees£11,832

Total excl. VAT£64,768

VAT (20%)£12,954

Total incl. VAT£77,721

Build cost breakdown

The £36,836 build cost from the estimate above, itemised by trade. Contingency, overhead, profit, site costs and VAT are shown in the Total Cost Estimate. Tap a stage to expand.

Build cost (excl. VAT)£36,836

Worth checking

Your interior rooms total about 19 m² but the loft-002 footprint is 15 m². If some rooms extend into the existing house, the quote may be slightly low — confirm with your builder. Otherwise the room sizes may be over-stated.
Floor finish for the bathroom is set to engineered-timber. Bathrooms typically use tile or LVT — engineered timber and carpet need additional sealing / moisture management and are unusual choices. Confirm with the builder before proceeding.

Inputs we assumed for you

You didn’t tell us about these, so we’ve used a typical default. If any are wrong, the quote will shift — adjust and re-run.

·Knock-through opening assumed: 3.5 m wide
·Window width assumed: 1.2 m
·Glazing assumed: standard
·We've assumed the soil stack stays in place.
·Bathroom floor level assumed: ground floor
·New radiators assumed: 4
·Velux rooflights assumed: 2
·Stair treads assumed: 13
·Secondary Velux rooflights assumed: 1
·FD30S landing-door upgrades assumed: 2
·Landing door upgrade method assumed: replace
·Roof covering assumed: tile

Assumptions made in this estimate

·The property is a detached house.
·Site access is good.
·Ground conditions are sandy gravel, requiring 1m deep foundations.
·The specification is mid-range.
·Costs are adjusted by +30% for the SW1A area.
·Contingency applies only to build costs, not professional fees.
·All costs shown exclude VAT unless stated otherwise.

A few things this estimate doesn’t model precisely

·Internal partition walls inside an extension or loft aren’t separately priced. Assume a small ±£500 swing on open-plan vs partitioned layouts.
·On a hallway-in-whole-house refurb, stairwell-void paint is currently undercounted by ~£200–£400. Builder will catch this on site.
·If your rooms physically straddle into the existing house, the quote may run slightly low. See “Worth checking” if shown.

Potential Considerations

These don’t change your estimate. They’re things to watch for.

Property Age (1920-1944)

medium

Older homes may have specific construction methods. Cavity walls might have older ties. Suspended timber floors need checking. Original windows may be single glazed.

Engineered Timber Flooring in Bathroom

medium

This flooring is not ideal for wet areas. Steam and water can cause damage over time. Waterproof options like tiles or vinyl are usually recommended.

Permitted Development Rights

low

Ensure your loft conversion falls under Permitted Development. Check if any restrictions apply to your property. A Lawful Development Certificate is advisable.

What to do next

1Confirm your total project budget.
2Appoint a structural engineer for detailed drawings.
3Obtain detailed quotes from reputable builders.
4Check if Permitted Development rights apply or if planning permission is needed.
5Apply for Building Control approval before starting work.

This report is an independent budgeting estimate for planning purposes only. It is not a builder's quote. Actual quotes from builders will vary and are commonly higher once detailed designs, site surveys, chosen finishes, and specific contractor rates are considered. Do not use this estimate to challenge or negotiate builder quotes.

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Example report — illustrative figures, not a real quote.Get your own — £1.99

Sample estimate · dormer loft conversion with 1 Bedroom, 1 Bathroom / En-suite

Your Loft Conversion Budget Estimate: A Clear Guide

Costs adjusted +30% for SW1A area (BCIS regional factor)~8 weeks on site396 labour hrs3 things to be aware of ↓

Total cost estimate

Low

£58,291

inc. VAT

Mid

£64,768

inc. VAT

High

£77,721

inc. VAT

Your estimated total cost, including VAT, could range from £58,291 to £77,721. The mid-point estimate is £64,768 before VAT, and £77,721 including VAT.

Build cost£36,836

Contingency (12%)£4,420

Overhead (12%)£6,371

Profit margin (10%)£5,309

Site costs & fees£11,832

Total excl. VAT£64,768

VAT (20%)£12,954

Total incl. VAT£77,721

Build cost breakdown

The £36,836 build cost from the estimate above, itemised by trade. Contingency, overhead, profit, site costs and VAT are shown in the Total Cost Estimate. Tap a stage to expand.

Build cost (excl. VAT)£36,836

Worth checking

Your interior rooms total about 19 m² but the loft-002 footprint is 15 m². If some rooms extend into the existing house, the quote may be slightly low — confirm with your builder. Otherwise the room sizes may be over-stated.
Floor finish for the bathroom is set to engineered-timber. Bathrooms typically use tile or LVT — engineered timber and carpet need additional sealing / moisture management and are unusual choices. Confirm with the builder before proceeding.

Inputs we assumed for you

You didn’t tell us about these, so we’ve used a typical default. If any are wrong, the quote will shift — adjust and re-run.

·Knock-through opening assumed: 3.5 m wide
·Window width assumed: 1.2 m
·Glazing assumed: standard
·We've assumed the soil stack stays in place.
·Bathroom floor level assumed: ground floor
·New radiators assumed: 4
·Velux rooflights assumed: 2
·Stair treads assumed: 13
·Secondary Velux rooflights assumed: 1
·FD30S landing-door upgrades assumed: 2
·Landing door upgrade method assumed: replace
·Roof covering assumed: tile

Assumptions made in this estimate

·The property is a detached house.
·Site access is good.
·Ground conditions are sandy gravel, requiring 1m deep foundations.
·The specification is mid-range.
·Costs are adjusted by +30% for the SW1A area.
·Contingency applies only to build costs, not professional fees.
·All costs shown exclude VAT unless stated otherwise.

A few things this estimate doesn’t model precisely

·Internal partition walls inside an extension or loft aren’t separately priced. Assume a small ±£500 swing on open-plan vs partitioned layouts.
·On a hallway-in-whole-house refurb, stairwell-void paint is currently undercounted by ~£200–£400. Builder will catch this on site.
·If your rooms physically straddle into the existing house, the quote may run slightly low. See “Worth checking” if shown.

Potential Considerations

These don’t change your estimate. They’re things to watch for.

Property Age (1920-1944)

medium

Older homes may have specific construction methods. Cavity walls might have older ties. Suspended timber floors need checking. Original windows may be single glazed.

Engineered Timber Flooring in Bathroom

medium

This flooring is not ideal for wet areas. Steam and water can cause damage over time. Waterproof options like tiles or vinyl are usually recommended.

Permitted Development Rights

low

Ensure your loft conversion falls under Permitted Development. Check if any restrictions apply to your property. A Lawful Development Certificate is advisable.

What to do next

1Confirm your total project budget.
2Appoint a structural engineer for detailed drawings.
3Obtain detailed quotes from reputable builders.
4Check if Permitted Development rights apply or if planning permission is needed.
5Apply for Building Control approval before starting work.