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Oak framed porches and screens, pegged oak.

Oak framed entrance porches, oak porch screens and doors, free-standing oak work in the garden, and repairs to frames already standing — from Washington, across West Sussex. Surveyed, priced and drawn by Tom Tennant. Joints cut into the timber, pegged, and left bare to weather.

An oak frame is cut, not bought in. The posts, the beam across their heads, the braces between the two and the roof above are shaped from solid timber and held together by joints cut into the wood itself, and that one decision governs the rest: what the frame stands on, how it meets the wall behind it, and what it does for the first few years after it goes up.

Tennant Carpentry & Building works from Washington, under the South Downs, on oak framed entrance porches, oak porch screens and doors, free-standing oak work in the garden, and repairs to frames already standing. A porch is rarely only the frame — there is brickwork under it and tiling over it — and both go in as part of the same job.

What if I only have a photograph of what I want?

That is a normal place to start, and it is all Tom needs to arrange a visit.

A drawing is welcome and so is an architect’s plan, but neither is needed. A photograph of a porch you have seen somewhere, a rough sketch, or a description of the opening you want covered is enough to arrange a visit.

The order is fixed, and it does not vary:

A visit to the house. Tom comes out to go through what you want, and to see what the frame would stand on and what it has to meet.
A written quotation for the work discussed, with the scope set out in it.
A detailed design. Tom draws the structure out once the job is agreed.
Cut, dry-assembled and raised.

The drawing comes after the quotation rather than before it. That means the design work happens on a job already agreed, and it means anything the drawing turns up that changes the scope is priced before a timber is cut. The garden room at Cranleigh was drawn by hand before it was cut — four views in pencil with a section size written against every timber.

A hand drawing in pencil showing four views of an oak framed garden room — a section through the wall, a section through the roof, and the front and back elevations — with the size of each timber written against it: 150 by 150 oak posts, 120 by 45 curved oak braces, 95 by 45 oak rafters and a cedar shingle roof. — Drawn by hand, every timber sized

What is the difference between green oak and air-dried oak?

Green oak is freshly sawn. It carries most of the moisture it had as a tree, it is softer to work, and it dries in place once the frame is up.

Air-dried oak has been stacked in sticks and seasoned, so it has done more of its moving already. In the sections a frame needs it is often not to be had.

Most external frames are cut from green oak, and there are good reasons for that. A post 150 millimetres square will not dry through in any timescale worth waiting for, green is the timber that can reliably be got in frame sections, and a frame built that way is designed around the drying rather than pretending otherwise.

The frames on this page are the exception. Air-dried is what Tennant Carpentry & Building prefers, and buys where the sections can be had. It does not shrink and change shape as much as green oak, so the frame holds nearer the shape it was cut to and the finish is better for it. The porches at Bolney and at Horsham and the garden room at Cranleigh, just over the county line in Surrey, were all framed in air-dried oak. It means waiting for the right sections, and the timber still moves — it just moves less.

Oak earns its place outside on its heartwood, which is durable untreated. The paler sapwood is not, and sections are chosen accordingly.

Will an oak frame crack as it dries?

It will, and that is better said beforehand than afterwards.

Oak shrinks across the grain and hardly at all along it. The outside of a beam gives up its moisture faster than the middle, and the timber relieves the difference by splitting along the grain — shakes, or checking. On the porch posts they are there to see. They run with the grain rather than across it, and are not the frame coming apart.

Colour moves as well. New oak goes up pale and honey-coloured, and ultraviolet takes it to silver-grey over the first couple of years, faster on the faces that take the weather.

An external frame is left bare because of that movement rather than in spite of it. The porch screen is the exception: its frame was finished to match the door hung in it. A film finish has to hold on to wood that is still shrinking underneath it, so it lets go first, and then has to be stripped back before anything else can go on.

Why is an oak frame pegged rather than bolted or screwed?

Because the timber is going to move and steel is not.

The joints are mortice and tenon, cut into the wood. The peg hole through the mortice and the one through the tenon are bored slightly out of line, so driving a cleft oak peg through pulls the tenon shoulder hard up against the post. That is draw-boring, and it is what makes the joint tight the day it goes together.

Then the frame dries. A tenon runs along the grain of the timber it is cut on, and along the grain oak barely shrinks, so the joint does not slacken lengthways. Across the grain the mortice closes on to what is in it. The peg is oak as well, cleft along the grain rather than sawn across it, so it moves with the frame instead of against it.

A bolt moves with nothing. The timber it clamps gets thinner as it dries, so the clamp loses its grip and has to be gone back to and tightened, because the steel is exactly the size it always was.

Oak also argues with steel. It is acidic, corrodes ordinary ferrous fixings and stains black around them, so a fixing that stays buried in the frame is stainless. Ironwork meant to be seen, like the strap hinges on the porch screen door, is a separate decision from the timber.

A corner of an oak frame from below: curved braces springing from the post up into the beams above, oak pegs left standing proud of the timber at each joint, and the post landing on a brick pier, with scaffolding and a hedge beyond. — Pegged, and standing on brick

What does an oak porch stand on, and how does it meet the house?

It depends on what is already there. At Bolney each post lands on a brick pier rather than on the paving — built in brick matched to the house, capped with a bullnose course, with dwarf walls between the piers returning to the wall, and two steps of stone paving up to the threshold. That height keeps the end grain of the post clear of the water that stands and splashes at ground level, which is where an external frame fails first. Where a post has to land at paving level instead, as at Horsham, the detail changes.

Where the frame meets the house, a second pair of braces runs back into the brickwork, so the porch is held both ways rather than leaning on the wall.

The tiling above is plain clay to match the existing roof. At Bolney the pitch is carried up into the main slope, so the two roofs run into each other at a valley on each side. At Horsham a single pitch dies into the wall instead, and that junction is lead, stepped into the brick courses.

Expect tannin. Rain off new oak carries it out of the timber and streaks the brick and paving below the beam ends, heaviest in the first year and easing as the oak weathers.

An oak framed entrance porch on a brick house seen straight on: silvered oak posts standing on brick piers with dwarf walls between them, curved braces up to the beam, a gabled tiled roof, a lantern either side and a plank door behind stone steps. — Posts on piers, clear of the ground

What stops a free-standing oak frame racking?

Braces. Four posts with a roof on top and nothing but air between them make a parallelogram until they are triangulated.

At the porch, curved braces spring from each post into the beam above, housed into both, so the load takes the shortest line to the ground through the post. At the well house in Rusper the braces run post to plate on all four sides, over a boarded deck on a brick and stone plinth, under the building’s own hand made clay tiles, taken off the rotten structure and sorted before they went back on so their variation reads as age rather than as a bad batch.

The braces look like the decorative part. They are the structural part. Nothing is lined or sheathed, so the geometry has to be right in the open, where every joint sits at eye height and the whole thing can be walked round in ten seconds.

Looking up into the corner of an oak frame: a curved brace either side of the post meeting the beam across their heads, with a boarded soffit and rafters above, against the brick wall and glazed door of the house behind. — The braces are the structural part

What is different about an oak porch screen and door?

A screen fills an opening rather than standing on its own feet. The one here sits in a brick porch opening: a panelled, studded oak door on black strap hinges, a glazed light either side, and a glazed head raking to a point under the gable.

The jambs and the door frame are square work. The head is not. Nothing in it meets at a right angle, the glazing rebate has to run round a corner that is not ninety degrees and stay in one plane while it does, and not one pane up there is a rectangle.

The door hangs on the screen rather than on the brickwork, putting its weight on the two posts either side of the opening, with the glazed lights outside them and the head spanning the lot.

Can a rotten post foot or sole plate be repaired?

Often, and usually it is only the bottom of it that needs anything. Frames fail at the wet end: a post foot standing in damp, or the sole plate under it.

The repair keeps the sound timber and lets a new length into it, cut long enough to have bearing and scribed to old timber that is neither straight nor plumb. At Pulborough that meant new oak sole plates lapped into what was left, and new posts under a frame jacked back to its original height.

New oak against old will not match for years — one is pale, the other has done all its weathering — so the junction is detailed to look deliberate while that happens.

At the barn saved from ruin at Pulborough the frame stayed open rather than boxed in, so every junction where new oak meets old is in plain sight, with no lining to hide one.

Will a porch need planning permission?

Whether a porch needs planning permission or Building Regulations approval turns on its size and height, how close it stands to a boundary or a highway, and what happens to the existing front door. It is worth establishing for your house before anything is drawn.

Glass for a raking head is measured off the frame once the frame is standing in the wall, rather than ordered from a drawing of the opening.

Work of this kind

Oak frame work

The front of the house mid-build: an oak framed porch in the middle carrying a pitched roof framed in softwood, with a flat roof deck running away on each side of it and scaffolding across the front.

Oak porch with pitched and flat roofs, Bolney

Bolney

A hand cut pitched roof over an oak framed porch, with a flat roof running away on either side of it, built while the house around it was still bare blockwork.

The finished barn: black feather-edge cladding over a rebuilt stone and brick plinth, under a hipped roof of corrugated tin, standing in grass at the edge of a wood.

A barn saved from ruin, Pulborough

Pulborough

A timber-framed barn taken back from collapse: the roof stripped to lighten it, the building jacked back to its original height, new base plates and posts let into the old oak frame, the stone walls rebuilt, and a tin roof chosen so it can come off again.

A finished oak framed garden room in a garden: an oak frame under a hipped roof of cedar shingles, cedar boarding to the closed sides, an oak spindle balustrade with a handrail along the open sides, a paved floor inside and a paved path up to it.

Oak framed garden room, Cranleigh

Cranleigh

An oak framed garden room in Cranleigh, designed and drawn by hand before it was cut: air dried oak on pegged mortise and tenon joints, a hipped cedar shingle roof, Canadian red cedar inside, and a drinks cupboard made to match the building.

A finished oak framed porch over a front door: two posts carrying a beam with curved braces, a single-pitch roof running back to the house wall, tiled in clay tiles with lead flashing along the abutment.

Oak framed porch, Horsham

Horsham

A single-pitch oak framed porch, designed and built by us: air dried oak frame, softwood rafters, and a painted ply soffit so the underside reads as a board rather than a membrane.

A finished oak framed entrance porch: two posts on brick piers carrying a beam, curved braces springing into it, a gable truss above with a king post and raking struts, roofed in plain clay tiles, over a pale green boarded front door with a lantern each side.

Oak framed porch, Bolney

Bolney

An oak frame cut with pegged mortise and tenon joints from air dried oak, raised on brick piers and roofed in plain clay tiles.

A rebuilt oak well house: four braced posts on a new boarded oak deck carrying a pitched roof of hand made clay tiles, with the original chain roller and bucket hanging beneath it.

Well house restoration, Rusper

Rusper

A rotten well house rebuilt to match the original: air dried oak frame, softwood rafters, the building's own hand made clay tiles put back, and the original gear for lowering the bucket kept and reused.