Ideas Factory/ the foundry

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nothing here is finished

Drone view at about 45 degrees over oak and birch woodland in late autumn, with mist between the trunks. The long gritstone wall runs through the trees from the walled tub enclosure at the top left, where steam rises off the round wooden tub and a heater sits in the corner, to the curved stone fire seat at the bottom right with the fire pit lit. The charred larch cabin sits on the middle of the wall with its moss and sedum roof blending into the leaves and its glass lit warm, and a path of wet setts runs underneath it. Off brief: the cabin runs along the wall rather than across it. The plans have it 11.4 m north to south across a wall running east to west, standing on the wall in the middle and on oak posts at each end.

← the floorif / 062·Real things·rendered

The Long Wall

A woodland weekend cabin across a 26 m stone wall, with a wood-fired tub at one end and a fire seat at the other.

drawing062made ofdrawing sheetplates7sheets5drawn9 Oct 2026houseunbuiltplanscostsgetaway

The sheet

the card's own material, at page scale

drawing 062 / Real things

The Long Wall

statusrendered
drawing062
sheets12
revA
issued9 Oct 2026
updates0

The brief

rendered · rev A

A weekend getaway for a couple, in wet English woodland. It was designed as an exploration, with no fixed budget, but costed honestly.

the idea

A 26 m gritstone wall runs through the woods, and a charred larch cabin sits across it, lifted a storey off the ground. The wall was there first. The cabin is a visitor.

The defining moment is bathing outdoors. A wood-fired tub sits in a stone enclosure at the west end of the wall. It is screened from the approach and open to the trees. At the east end the same wall shelters a stone fire seat. So there is fire at one end and water at the other, with the cabin bridging between them.

Everything wet and heavy happens in stone at ground level. Everything warm and dry happens in timber above. A warm stone lobby joins the two, so you step out of the tub and climb straight up into the heat.

the brief

Topic Decision
Users A couple, weekends and holidays
Setting Wet British woodland: oak, birch, moss, heavy rain, mild winters
Anchor moment Bathing outdoors in a wood-fired tub
Base Rough Pennine gritstone, dry-stone style coursing
Upper level Charred larch (shou sugi ban)
Roof Low pitch, deep overhangs, moss and sedum
Layout Open living with a proper small kitchen, separate bedroom, wet room upstairs
Glazing Generous, all round
Heating Air source heat pump for background, wood stove for atmosphere
Interior Warm and dark, oiled oak, cocooning
Arrival Under the cabin, straight into a stone lobby
Route from tub Through the warm lobby and up an enclosed stair
Wall ends Tub enclosure to the west, fire seat to the east

the site

The wall runs east to west. North of it is the approach, with the track, the parking and the heat pump tucked into a recess in the wall. South of it is the private woodland side, where the glass, the tub and the fire seat face the trees and the light.

The wall is 26 m long, 600 mm thick and 2.4 m high, rising to 2.8 m around the tub. No opening ever breaks it, so it reads as an old boundary rather than part of the house.

The cabin goes in an existing gap in the trees. Nothing over 150 mm in diameter is felled, and the foundations are piled to stay out of the root zones.

the accommodation

About 80 m² of heated space: 63 m² upstairs in timber and 17 m² in the stone core below. The upper volume is 11.4 by 6.6 m. It sits across the wall with its finished floor 2.85 m above the ground.

Space Level Size Area
Living, dining and kitchen Upper 6.0 × 5.8 m 35 m²
Bedroom Upper 3.6 × 4.0 m 14 m²
Wet room Upper 2.4 × 2.4 m 6 m²
Landing, coats and store Upper 8 m²
Stone lobby and drying room Ground 3.6 × 2.6 m 9 m²
Stair Ground to upper 1.0 m wide 4 m²
Plant and laundry Ground 1.8 × 2.4 m 4 m²
Tub enclosure, outdoor Ground 5.4 × 5.0 m 27 m²
Sheltered undercroft, outdoor Ground 50 m²
Fire seat terrace, outdoor Ground 20 m²

The concept table gives the bedroom as 3.6 × 4.0 m, but the upper plan labels it 3.6 × 4.1 m. Neither has been chosen yet.

the structure

The cabin stands on the wall down its middle and on four oak posts at its ends. Every span is under 6 m, so nothing here is exotic or experimental.

  1. Foundations. Steel screw piles with a reinforced concrete ground beam under the wall, and single piles under each post. Screw piles go in without trenching. That protects the tree roots and avoids the 1 m deep strip footings a heavy wall would normally need.
  2. The wall. A 215 mm dense concrete block core, faced on both sides with gritstone and tied through with long bonding stones, 600 mm thick overall. Large flat copings on top, left to grow moss. It is honest masonry, not stone cladding on a stud wall.
  3. The stone core. Where the wall crosses under the cabin, it thickens into a box that holds the lobby, the stair and the plant room. Here the cavity is insulated, so the core is warm inside and stone on both faces.
  4. Oak posts. Four green oak posts, 250 × 250 mm, on stainless steel shoes lifted 150 mm clear of the ground, so the end grain never sits in water.
  5. Floor. Glulam beams span 5.7 m from the wall to the posts at each end and carry a 140 mm cross-laminated timber (CLT) floor. Insulation sits under the CLT, protected by a ventilated larch soffit.
  6. Walls. A 220 mm timber frame filled with wood fibre insulation, then a ventilated cavity, then charred larch.
  7. Roof. Glulam rafters and a CLT deck at an 8 degree pitch, falling north. The CLT cantilevers 1.8 m on the south side and 1.2 m elsewhere to form the deep eaves. A saturated moss and sedum roof weighs roughly 120 to 150 kg/m², which is the main reason the roof structure is heavier than a normal cabin's.

An engineer would need to confirm all the sizes. They are proportioned to be realistic, not calculated.

materials and weathering

Every material was picked because it gets better, or at least no worse, in rain and shade. Nothing here needs painting.

Material Where Year 1 Year 10 Upkeep
Pennine gritstone Wall, core, tub enclosure, fire seat Warm buff brown, crisp edges Greened, lichen, moss on copings Repoint lime joints every 30+ years
Charred larch Upper walls Deep black, slight sheen Softer black, grain raised Re-oil every 10 to 15 years
Green oak Posts, front door, handrails Honey Silver grey, fine cracks None
Riven slate Wet room, kitchen worktop Blue black Unchanged Seal worktop yearly
Moss and sedum Roof Green, patchy Fully knitted, self-seeded Check outlets after leaf fall
Gritstone setts Undercroft, enclosure floor Clean Moss in joints Jet wash if slippery
Oiled oak Interior floors, joinery Golden Darker amber Re-oil floors every few years

One practical rule: char rubs off on hands and clothes. So anywhere people touch at the entrance, the timber is green oak, not charred larch.

heating, services and water

The cabin warms itself before you arrive, and the stove takes over once you are there.

  • Heat pump. A small air source unit, around 5 kW, hidden in a recess on the north face of the wall. It keeps the cabin at a low background temperature and is turned up remotely the day before a visit.
  • Distribution. Underfloor heating in the stone lobby, low-temperature radiators upstairs, and a towel rail in the wet room.
  • Stove. A 5 to 6 kW wood stove in the living space, with an external air supply so it doesn't pull cold air through the glazing.
  • Glazing. Triple-glazed timber aluminium frames, oak inside and dark bronze outside. With this much glass, the glazing does more than anything else to keep the heating bills sane.
  • Hot water. A cylinder in the ground floor plant room, fed by the heat pump.
  • Foul drainage. A small package treatment plant. Woodland sites rarely have a sewer.
  • Tub water. Drained and refilled every few visits. It is left to cool first, then sent to a planted soakaway rather than straight into the ground.
  • Power. A grid connection is assumed. Solar is a poor fit under a tree canopy.

cost

Approximate build cost is £350k to £540k. With fees and contingency, a realistic total is roughly £420k to £650k. That is higher than the £250k to £400k first quoted, because the long wall, the enclosure and the fire seat add a lot of hand-laid stone beyond the cabin itself. These are UK 2026 ballpark figures from experience, not a quantity surveyor's estimate.

Element Low High Main driver
Site set-up, access track, tree and ecology surveys £25k £40k Getting machines into a wood
Screw piles and ground beams £20k £30k Root protection
Gritstone wall, core, enclosure, fire seat £70k £110k About 235 m² of hand-laid stone face
Timber structure: glulam, CLT, oak posts, frame £70k £100k Heavy roof load
Planted roof £15k £25k Drainage edge and membrane
Triple glazing £40k £65k Glass on all sides
Charred larch cladding £12k £18k Supply and fix
Interiors: kitchen, wet room, joinery, floors £45k £70k Bespoke oak joinery
Services: heat pump, stove, electrics, treatment plant, utility connections £35k £60k Distance to the grid
Tub, heater, enclosure fit-out £10k £18k Tub specification

If this ever became real, there are two cost levers. Shortening the wall to 18 m saves roughly £20k. Dropping the fire seat to a simple stone ring saves roughly £8k. The tub enclosure should be the last thing cut.

risks

  • Planning. This is the big one. New isolated homes in the English countryside are normally refused. A holiday let on land you already own, or replacing an existing structure, is a more realistic route.
  • Trees and wildlife. Expect a tree survey, a root protection plan and bat surveys before any design is fixed.
  • Leaf fall. Even with a planted roof, the outlets and gutters need clearing every autumn.
  • Damp. The stone core sits in a wet wood. The insulated cavity and the lifted timber are there to stop moisture tracking into the cabin.

the render prompts

Six prompts for an image generator. Each one repeats the core description so the images stay consistent. Generate the first, then attach it as a reference for the rest.

1. Arrival, north side, rainy afternoon

Photorealistic architectural photograph of a small woodland cabin in wet English oak and birch woodland, overcast rainy afternoon. A long rough Pennine gritstone wall, 2.4 m high and 26 m long, dry-stone style coursing, moss on its flat stone copings, runs left to right through the trees. A single storey cabin clad in charred black larch (shou sugi ban) sits across the wall, lifted 2.85 m off the ground, resting on the wall in its middle and on thick weathered silver oak posts at its ends. Very low pitched roof covered in moss and sedum with deep overhanging eaves. Sheltered space beneath the cabin with gritstone setts underfoot and a plain oak door set into a stone core. Wet ground, ferns, fallen leaves, soft diffuse light. Shot at eye level on a 35mm lens. Calm, authentic, not luxurious or showy.

2. Woodland side, south, golden hour

Photorealistic architectural photograph of the south side of a charred black larch cabin raised a storey above a rough gritstone wall in English oak woodland, low autumn evening sun through the trees. The upper level has generous floor-to-ceiling triple glazing with dark bronze frames, glowing warm inside. Deep 1.8 m roof overhang with a moss and sedum roof. Thick silver oak posts at each end. To the left, the stone wall wraps into a walled outdoor bathing enclosure. Moss, bracken, birch trunks, leaf litter. Shot from 20 m away at eye level, 35mm lens. Quiet, grounded, honest materials.

3. The tub at dusk in the rain (hero image)

Photorealistic photograph inside a roofless walled stone bathing enclosure in an English woodland at blue hour, light rain falling. Rough buff Pennine gritstone walls 2.8 m high on two sides, dropping to a low 0.9 m wall on the open side facing the trees. A round wooden hot tub, sunk partly into a gritstone sett floor, steam rising from the water. A small wood-fired heater glows in a niche cut into the stone wall. Above and to one side, the charred black larch cabin with warmly lit windows, rain dripping from its deep eave. Oak and birch trunks beyond, moss on the wall tops. Shot at seated eye level from the tub's edge, 24mm lens. Moody, intimate, real.

4. Living space interior, winter evening

Photorealistic interior photograph of a small woodland cabin living room at night in winter. Warm and dark palette: oiled oak floorboards, dark stained larch ceiling following a very shallow roof pitch, a black steel wood stove burning on a raised rough gritstone hearth. A low deep linen sofa faces floor-to-ceiling triple glazing with dark frames, looking out to dark woodland lit softly from outside. A 4 m dark oiled oak kitchen run with a riven slate worktop at the back. Warm 2200K lamp light, no ceiling downlights, wool throws, a few books. Shot at seated eye level, 24mm lens. Cosy, textured, uncluttered, not minimalist or cold.

5. Stone lobby, stepping in from the tub

Photorealistic interior photograph of a small stone lobby at the base of a woodland cabin. Rough gritstone walls, a warm gritstone floor still wet with footprints, an oak bench, linen robes on deep oak pegs, a heated towel rail. An oak door half open to a walled outdoor bathing area with steam and trees beyond. An enclosed oak stair rises into the warmth above, lit by a narrow slot window. Soft warm light, evening. Shot at eye level, 28mm lens. Simple, tactile, real.

6. Aerial, late autumn

Photorealistic drone photograph looking down at 45 degrees on English woodland in late autumn. A long rough gritstone wall runs through the trees. A charred black larch cabin with a moss and sedum roof sits across the middle of the wall, the roof blending into the forest floor. At the west end the wall wraps into a walled bathing enclosure with a round wooden tub; at the east end a curved stone bench faces a fire pit. Copper and yellow leaves, mist between the trunks. Calm, sensitive to the landscape.

Avoid in every prompt: glass balconies, white render, timber decking, hot tub covers, cars, people posing, fairy lights, and anything that reads like a holiday park lodge.

The plates

7 · lift any one out
Drone view at about 45 degrees over oak and birch woodland in late autumn, with mist between the trunks. The long gritstone wall runs through the trees from the walled tub enclosure at the top left, where steam rises off the round wooden tub and a heater sits in the corner, to the curved stone fire seat at the bottom right with the fire pit lit. The charred larch cabin sits on the middle of the wall with its moss and sedum roof blending into the leaves and its glass lit warm, and a path of wet setts runs underneath it. Off brief: the cabin runs along the wall rather than across it. The plans have it 11.4 m north to south across a wall running east to west, standing on the wall in the middle and on oak posts at each end.
01 · Drone view at about 45 degrees over oak and birch woodland in late autumn
The south side at golden hour, from the woodland floor about 20 m away, with low sun coming through the trees from the left. The cabin is raised over the mossy gritstone wall on thick silver oak posts, with five tall panes of glass in dark frames glowing warm, a dining table and a fire visible inside, and a deep eave under the moss roof. On the left the wall steps up into the tub enclosure with steam rising from it. Bracken, mossy boulders and birch trunks fill the foreground. Off brief: as in the aerial, the cabin runs along the wall rather than across it, so its long glazed side faces south. The south elevation has the 6.6 m end facing south with four panes.
02 · The south side at golden hour
A rainy afternoon at the arrival side. The charred larch cabin is lifted over the long gritstone wall, with moss on the copings, on two thick weathered oak posts. It has a moss roof with deep eaves. Underneath, a plain oak door with a small wall light is set into the stone, with wet flags, ferns, birch trunks and fallen leaves around it. Off brief: the door is in the face of the long wall rather than in the north face of the stone core, the cabin sits along the wall rather than straddling it, the north face has a long band of glass where the upper plan has one low bedroom window, and the floor is irregular flags rather than setts.
03 · A rainy afternoon at the arrival side
The hero view, from the edge of the tub at blue hour in light rain. Steam rises off the water in the round wooden tub. Mossy gritstone walls surround it, the setts are wet, and lanterns and a folded blanket sit on an oak bench. Beyond the low wall there are oak and birch trunks. Above on the left, the charred larch cabin has lit windows with books and plants behind them, a deep eave and an oak post. Off brief: the fire is an open fireplace built into the enclosure wall with logs stacked under it, where the brief has a wood-fired heater in a niche stoked from outside. The tub's rim also stands well above the setts, where the brief has the tub set 600 mm into the floor.
04 · The hero view
The stone lobby in the evening, coming in from the tub. Rough gritstone walls, a wet stone floor with puddles, linen robes on oak pegs over a rough oak bench with slippers under it, and a dark heated towel rail on the stone. The oak door stands open onto the tub enclosure, with the steaming tub, a lantern and trees beyond. An enclosed oak stair rises on the right toward a tall slot window, with light along the treads. Off brief: there is a recessed downlight in the ceiling, where the brief rules out ceiling downlights, and the floor is large flags where the ground plan has heated setts.
05 · The stone lobby in the evening
The living space on a winter night. A deep brown linen sofa with wool throws on a jute rug, a heavy oak coffee table with a candle and books, an armchair with a sheepskin, and a black wood stove burning on a long raised gritstone hearth on the right. Floor-to-ceiling glass looks out to woodland. At the back there is a dark oak kitchen run with a lit shelf and a dining table with wishbone chairs, all under a dark timber ceiling. Off brief: the trees outside are dotted with sparkling points of light that read as the fairy lights the brief rules out.
06 · The living space on a winter night
Materials board, sheet 06. Eight swatches, each with where it goes. Pennine gritstone for the wall, core and enclosure. Charred larch for the upper walls. Moss and sedum for the roof and wall copings. Weathered green oak for posts, doors and handrails. Riven slate for the wet room and worktop. Oiled oak for floors and joinery inside. Gritstone setts for the undercroft and enclosure floor. Dark bronze frames for all the glazing.
07 · Materials board

The model

drag to turn it · built from the drawings
Screenshot of the 3D model from the south, untextured, on a dark ground. The long gritstone wall with moss copings runs left to right among oak and birch trees, the tub enclosure at its west end and the curved stone fire seat at its east. The charred larch cabin sits across the wall on the stone core and four oak posts, its tall south glass showing the living space, under a moss roof that oversails to the south.

the model loads as you reach it

The drawings

5 sheets
Site plan, sheet 01, at 1 to 500, north at the top. The gritstone wall, 26.0 by 0.6 m, runs east to west among the trees. At the west end it wraps into the tub enclosure with the tub and heater. The cabin footprint sits across the wall over the stone core, with its oak posts at the four corners and the roof overhang dotted around it. The heat pump is in a recess on the north face, the approach track comes in from the north, and the curved fire seat with its fire pit is at the east end. North is arrival and services, south is the private woodland side.
01 · Site plan
Ground floor plan, sheet 02, at 1 to 100, north at the top. The stone core sits where the wall crosses under the cabin. Inside it are the plant room with the cylinder and laundry, a north entry door off the covered arrival, a stair of 14 risers rising west to east, and the stone lobby with an oak bench and a door west into the tub enclosure. The enclosure has the 1.8 m tub, the heater niche, the log store and a slot drain. Setts run under the whole cabin, which is drawn dashed at 6.6 by 11.4 m with an oak post at each corner, and the heat pump sits against the wall to the east.
02 · Ground floor plan
Upper floor plan, sheet 03, at 1 to 100, north at the top. In the north are the store for coats and linen, the wet room with shower and vanity, and the bedroom, labelled 3.6 by 4.1 m, with its bed against the east glass and a low window in the north wall. The stair comes up in the middle to a landing. The south half is living, with a 4.0 m kitchen run along the west wall and a sink window looking down into the tub, a dining table, a stove on a gritstone hearth against the east wall, and a sofa facing the full-width south glass. The roof edge is dotted 1.2 m out, and 1.8 m on the south.
03 · Upper floor plan
Section A-A, sheet 04, at 1 to 100, north on the left. The ground is at +0.00 with screw piles below it. The stone core walls carry the floor, the plant room and lobby are inside, and the long wall is beyond at +2.40. Oak posts stand at each end. The glulam and CLT floor is at +2.85, with the bedroom to the north and the living space to the south. The moss and sedum roof on CLT rises at 8 degrees from +5.35 at the north wall to +6.95 over the triple glazing on the south, and oversails it by 1.8 m. Figures show the scale.
04 · Section A-A
South elevation, sheet 05, at 1 to 200. The 26.0 m wall is 2.4 m high with moss on its copings and rises to 2.8 m round the tub enclosure at the west end, where the heater flue and steam show over a 0.9 m front wall. The charred larch cabin sits over the stone core on oak posts, with four tall panes of glass and a planted roof edge. The curved fire seat is at the east end with a figure beside it for scale.
05 · South elevation

The spaces

4 · each has a page of its own