• A long tape measure (at least 30 metres)
• A notepad and pen for recording measurements
• A helper (measuring is much easier with two people)
• Your property's original plans if available
• A ladder for measuring height (if safe to do so)

The most important concept in GPDO measurements is the "original dwelling". This refers to your house as it was first built or as it stood on 1st July 1948 (whichever is later).

Many mistakes happen because people measure from the current dwelling, not the original. Any previous extensions don't count as part of the "original dwelling".

**Step 1:** Identify where the original rear wall was. Look for changes in brickwork, roof lines, or check old planning records.

**Step 2:** Measure from the original rear wall (not the current one if extended) to the proposed furthest point of your new extension.

**Step 3:** Record this measurement in metres.

**For Permitted Development:** • Single storey: Up to 4m (detached) or 3m (semi/terraced) without prior approval • Single storey with prior approval: Up to 8m (detached) or 6m (semi/terraced) • Two storey: Maximum 3m for all property types

**Overall Height:** Measure from ground level to the highest point of the roof.

**Eaves Height:** Measure from ground level to where the roof meets the wall (the eaves line).

**For Single Storey Extensions:** • Maximum overall height: 4 metres • Maximum eaves height: 3 metres • If within 2m of boundary: Both eaves and overall height limited to 3 metres

You'll need to measure the distance from your proposed extension to:

• **Rear boundary:** Two-storey extensions must be at least 7m from the rear boundary
• **Side boundaries:** Side extensions must maintain a 1m gap, and be single storey only