Oak Frame Porch

Open or enclosed

An open porch is a roof on posts. It keeps rain off the step, frames the door and needs almost no groundwork: the posts sit on stone pads or on low brick walls either side of the path. Because nothing is glazed or heated, it is the purest piece of oak framing on this site and the easiest to get right.

An enclosed porch is a very small room. It needs a floor slab, glazed or boarded sides, an outer door and proper weathering where its roof meets the house. It costs roughly twice as much as an open one of the same footprint, and it is where a size limit starts to matter.

The 3 m² rule

In England a porch on any external door is permitted development if three things are true. Its ground area, measured externally, is no more than 3 m². No part is higher than 3 m above the ground. And no part is within 2 m of a boundary that fronts a highway. The Planning Portal sets these out.

Three square metres is smaller than it sounds: about 2 m wide by 1.5 m deep, measured to the outside of the walls or posts. A steep gabled roof over that footprint can reach 3 m quickly, so check the ridge height on the drawing. If the door is close to the road, the 2 m rule may rule out permitted development altogether.

A listed house needs listed building consent for any porch, however small, and a conservation area may have an Article 4 direction that removes the allowance. Flats and maisonettes have no permitted development rights for porches. Scotland allows a similar 3 m² porch, though the rules are tighter in a conservation area.

Building regulations

A porch at ground level with a floor area under 30 m² is normally exempt from the Building Regulations, on one condition that people often miss: the existing front door must stay in place between the house and the porch. Take that door out and the porch becomes part of the heated house, and the insulation rules apply to it.

Even when the structure is exempt, any glazing in or beside a door has to be safety glass, and new electrical work for a porch light must be done to the wiring regulations.

Getting the proportions right

Most disappointing porches are too small in the timber and too shallow in the roof. Posts of 150 mm square look right on a two-storey house; 100 mm posts look like a garden pergola. The roof pitch should match the main roof or be steeper, never flatter.

Match the tiles or slates to the house. A handful of reclaimed tiles for a roof this small costs little and makes the porch look as if it has always been there. The lead flashing where the porch roof meets the wall should be cut into a mortar joint, not stuck to the face of the brickwork.

On stone pads, the foot of each post should be lifted 100 to 150 mm clear of the ground so that it dries out after rain. Oak lasts for centuries in the air and only a few decades standing in a puddle.

How the oak will change

A porch is outdoors, so it weathers faster than a frame inside a room. The pale, slightly pink colour of fresh oak turns to silver-grey in two or three years. Brown tannin will wash out in the first few months and can streak a stone step or pale paving; it fades, and a stiff brush speeds it along.

Splits will open along the posts in the first two summers. They are expected and do not weaken anything. If you prefer the oak to stay golden, an exterior oil with a UV filter will hold the colour, but it must be reapplied every couple of years. Left alone, oak looks after itself. Our guide to green oak explains why.