An oak carport is worth specifying properly because it carries its own structural load without a single wall to share the work. Without cladding to brace it, the strength of an open frame rests entirely on the quality of its joints and the grade of its timber, so the decisions that seem cosmetic, bay width, roof pitch, timber specification, actually determine whether the building serves you for one generation or several. Getting these decisions right at brief stage costs nothing extra. Correcting them later is expensive.
A carport is often treated as the simpler build. No walls to clad, no doors to hang, no floor to pour. If that’s how you’re looking at it, the simplicity can start to feel like an argument for spending less on the frame. It should be the opposite. An open oak carport is exposed to weather on all four sides. Rain falls on the roof and runs down the posts. Wind loads the structure from every direction. The joints cycle through wet and dry seasons for decades, with nothing to share the structural work. The frame does it alone. That is the argument for specifying properly, not for spending more than a project needs, but for understanding where quality actually matters in a building like this.
What structural grade actually means for your carport frame
Structural oak used in framing in the UK is graded under BS 5756, the British Standard for visual strength grading of hardwood timber. The standard sets out grade categories for hardwood sections, assessed by a certified grader for knot size, grain slope and other physical defects. Not all timber sold for oak frame construction is formally graded this way. Some suppliers describe their timber as structural oak without any certification behind the description, and the difference is not always visible to the eye.
Structural hardwood in the UK is visually strength graded to BSI’s current published standard for visual strength grading of temperate hardwood, BS 5756:2007. The standard sets out two general structural grades, TH1 and TH2, for hardwood sections under 20,000mm² in cross-section, and two heavier grades, THA and THB, for larger sections. TH1 is the higher of the two general structural grades. Brookwood specifies TH1/D30 beaming oak throughout, and the specification is agreed before any project begins.
A graded frame comes with a verified chain of custody back to a certified grader. An ungraded frame does not, whatever the supplier’s description says. Green oak is the correct material choice for structural frames of this type, whether you’re specifying an oak carport or an oak framed garage. It is easier to work than fully seasoned oak, which matters when cutting mortices and tenons to close tolerances, and it behaves in a way that makes the joints stronger over time rather than weaker. A seasoned frame has already moved through most of its drying process before it is raised, so it cannot tighten the same way a green oak frame does as it dries.
Why an open frame asks more of its joints, not less
A closed oak building has cladding on three or four sides, and that cladding adds racking resistance, helping the structure resist the lateral forces that wind puts through a frame. A carport has none of that. The frame resists lateral load through the rigidity of its joints alone, which makes the quality of the joinery a structural necessity rather than a matter of finish.
Traditional mortice-and-tenon joinery, secured with handmade tapered oak pegs, handles this loading well. The tenon is cut to a precise fit within the mortice, and the peg holes in the tenon and mortice are drilled at a deliberate offset. When the peg is driven, it draws the tenon deeper into the joint, a technique known as draw-pegging. As the green oak dries over the first few years and shrinks across its width, the offset pulls the peg tighter, and the joint tightens further as the timber seasons. A properly built, draw-pegged carport frame is structurally stronger several years after it is raised than it was on the day it went up.
Published drying shrinkage values for oak, from green to around 12% moisture content, sit at approximately 4.5% radially and 7% tangentially, according to TRADA and the Forestry Commission’s guide to green oak construction. It is this movement across the grain, not along it, that the draw-peg’s offset hole is designed to use: as the timber shrinks radially and tangentially, it draws the peg, and with it the tenon, tighter into the mortice.
A frame assembled with bolted connections, or machine-cut joints that do not draw-peg, does not improve over time in the same way. It may be entirely adequate when new, but it will loosen as the oak moves rather than tighten with it. We use mortice-and-tenon, large wedge dovetail, wedge stop splayed, and wedge compound stop splayed scarf joints in every frame we build, and these choices are the technically correct response to how green oak behaves in a structure exposed to weather for generations. You can read more about the joinery and grade specification we use in every frame.
Bay width and the modern vehicle problem
Most standard oak carport designs quote a bay width of around 2.8 to 3.2 metres, a figure rooted in reference points that are now several decades old. A standard bay provides enough width to park a modern car, but it does not always provide enough width to open all four doors without restriction, or to walk around the vehicle without turning sideways.
In a two-bay carport, the centre post is where the problem shows most clearly. Two modern SUVs parked in adjacent standard bays will leave a tight gap at that post, and if the vehicles are wide, or if you are retrieving something from the boot, the carport ends up working against you rather than for you. If you plan around the vehicles you have now rather than the ones you might have in ten years, the building can become a daily annoyance for the rest of its life.
We developed the SuperSize range specifically to address this. The SuperSize oak garage and carport range shares the same wider-bay specification: bay widths exceed 3.66 metres, or 12 feet, the point at which a modern SUV driver can open all four doors without restriction. A wider bay requires a different structural specification, because the tie beams and rafters carry greater span loads, so the frame has to be designed for the width from the outset rather than adapted to it afterwards. Bay width is worth discussing before the brief is agreed, whatever oak carport layout you’re considering. Changing it after the frame is designed is a structural alteration, not a minor adjustment. You can check the full spec against our SuperSize specification.
What planning permission actually requires for a carport
Most oak carports built in residential settings qualify for Permitted Development under the Permitted Development rules for outbuildings, Schedule 2, Part 1, Class E of the Town and Country Planning (General Permitted Development) (England) Order 2015. This means formal planning permission is not typically required, provided the conditions are met.
The conditions are: single storey only, eaves no higher than 2.5 metres where the building is within 2 metres of a boundary, a maximum overall height of 4 metres for a dual-pitched roof, and a combined footprint for all outbuildings that does not exceed 50% of the curtilage. The carport also cannot be positioned forward of the principal elevation of the house. These conditions apply to standard residential properties, and they cover most carports built in ordinary gardens.
Properties in conservation areas, National Parks, and listed building curtilages operate under different rules, where Permitted Development rights are restricted or removed and a full planning application is typically required instead. Oak often receives a sympathetic assessment in these heritage contexts, because it is a traditional material with centuries of use in English construction and it weathers to a silver-grey patina that sits comfortably within a historic setting. That does not mean approval is guaranteed, and the specifics vary by local authority. If your property sits in one of these settings, we manage the planning process as part of a full Zone One project, from the first application to the decision notice, through our planning service.
What separates a carport built to last from one built to a price
When you start comparing oak carport options, you will encounter a wide range of prices, and the gap is rarely about how the buildings look on the day they are raised. At one end sits a kit: a pre-cut frame supplied for a builder to erect, at standard bay widths, with joinery designed for ease of manufacture rather than structural longevity. At the other end sits a bespoke oak carport, designed for your specific site, cut in grade-specified timber, and erected by craftsmen who have been doing this single thing for over two decades.
Both buildings may look similar on the day they go up. The difference shows at the ten and twenty year mark, in how the joints have moved, how the frame has settled, and whether the building feels permanent or provisional. A kit price is typically frame-only, so the headline figure you compare against a bespoke quote is rarely comparing the same thing. We publish the grade of our timber, which is not something every builder will do, because a frame you can stand behind is one whose material is on the record rather than described as premium and left at that.
Our bespoke carports are pre-assembled in full at the workshop before delivery, so every joint is confirmed to fit before the frame reaches your site. The price agreed after the site visit does not change unless the specification changes. We have been a verified member of the Guild of Master Craftsmen since the company was founded in 2003, and every frame carries a 10-year structural guarantee on the oak timberwork. You can find out what a fixed-price oak frame typically costs before you commit to anything.
Talk to us about your carport
A site visit is free and takes a morning. It’s the point where a carport brief stops being a general idea and starts becoming a building designed for your property, your vehicles, and your site, with a price that holds once it’s agreed.
Arrange a site visitFrequently Asked Questions
Do I need planning permission for an oak carport?
Most oak carports qualify for Permitted Development under Schedule 2, Part 1, Class E of the Town and Country Planning (General Permitted Development) (England) Order 2015, so formal planning permission is not typically required. The main conditions are that the carport is single storey, with eaves no higher than 2.5 metres near a boundary and an overall maximum height of 4 metres for a dual-pitched roof, and that the total outbuilding footprint does not exceed 50% of the curtilage. It also cannot sit forward of the principal elevation of the house. Properties in conservation areas, National Parks, and listed building curtilages operate under different rules and will typically need a full planning application.
What bay width do I need for a modern SUV in an oak carport?
A standard bay width of 2.8 to 3.2 metres gives you enough clearance to park a modern vehicle, but not always enough to open all four doors without restriction. For comfortable access with full door clearance, look for a bay width of at least 3.66 metres, or 12 feet, which is the specification of the SuperSize range developed for modern SUVs and larger vehicles. If you drive a large SUV, or expect to, specifying the wider bay from the outset matters, because changing bay width after the frame has been designed is a structural alteration rather than a minor adjustment.
Will green oak crack in an outdoor carport?
Yes, green oak splits and develops surface fissures, known as shakes, as it dries, and an open carport frame goes through this process in full view of the weather. These fissures are cosmetic and do not affect the structural integrity of the timber. The draw-pegged mortice-and-tenon joints used in a properly built carport are designed with peg holes in the tenon and mortice drilled at a deliberate offset, so that as the oak dries and shrinks across its width, the peg draws the joint tighter. After several years, the joints of a properly built carport frame are mechanically stronger than they were when the frame was raised, and the shakes you see are visible evidence that the process is working as intended.
What is TH1/D30 grade oak and why does it matter?
TH1 is a visual structural grade for hardwood under BS 5756:2007, the British Standard for visual strength grading of hardwood, covering sections under 20,000mm² in cross-section. Timber graded to this standard has been assessed by a certified grader for knot size, grain slope, and physical defects, giving a verified basis for the section sizes a frame needs to carry its loads safely. Not all oak sold for structural use is formally graded this way. Asking a builder for the grade of the timber in writing, rather than a general description like “structural oak,” is a legitimate question to raise before you commit.
What is the difference between a bespoke oak carport and a kit?
An oak carport kit is a pre-cut frame supplied for erection by you or your builder, at standard bay widths, with joinery designed for ease of manufacture. A bespoke carport is designed for your specific site and brief after a site visit, with the structural specification, joinery type, bay width, roof pitch, and timber grade all agreed before cutting begins. Bespoke carports are typically pre-assembled in full at the workshop before delivery, confirming that every joint fits before the frame reaches your site, and the price is fixed after the site visit and agreed specification.
