Tennant Carpentry & Building

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Hand cut and trussed roofs, framed here.

Roof structure in timber: hand cut roofs set out on the building as it measures, trussed roofs fixed and braced, and the openings trimmed through either. Surveyed and priced by Tom Tennant, and built by the team and the specialist trades this business has worked with for years.

A roof is two things stacked on each other, and this page is the one underneath: the timber that makes the shape, not the tiles that keep the water off it. It is either cut on site from loose timber, off the building as it actually measures, or made off site as a set of designed trusses and fixed in place. Both get built here, and they are different jobs rather than a better and a worse one.

New roofs, roofs altered or repaired, and the openings trimmed through them. Tom surveys and prices the job from Washington, across West Sussex, and stays on it while it is built. The work is carried out by the team and by the specialist trades this business works with regularly, all of it from that survey rather than from a job pack handed on.

What is a hand cut roof?

A pitched roof set out and cut where it stands. A wall plate is levelled along the top of the wall, and rafters run from it up to a ridge board. Purlins run the other way underneath, carrying those rafters mid-span, with struts propping the purlins off a wall below. Collars tie opposing rafters across, and hips and valleys turn the corners. The drawings fix the geometry where there are drawings — where the ridge sits, how steep the slopes are, where the hips fall — but the lengths and the bevels are marked and cut on site, off the building as it actually measures.

It is chosen because it lands on a building that is not square, takes a shape that would be awkward to order, and can be set out around what is already there.

Cuckfield is the worked example: rafters running down to a wall plate and up to a ridge that stops at the chimney, a hip worked in at the far end, both slopes framed, sole plates set out on the boarded deck. Three sides of that frame landed on something already there, so the cuts came off the building rather than off the drawing.

A cut roof frame standing behind a new first floor: rafters running up to a ridge over blockwork walls, with floor joists laid across steel beams in front of it and a stepladder and trestle standing on the deck.
Cut on site, over a new floor

What changes when a roof is trussed?

A trussed rafter roof is designed before it is made. A supplier takes the span and the loads, and the trusses come back as a set of engineered frames: rafter, ceiling tie and a lattice of webs between them. They are craned in where a crane can reach — and where one cannot, they go up by hand: at Horsham a low overhead cable ruled the crane out and every truss was lifted in by hand. Then they are fixed at centres, braced and binder-tied as part of the design rather than as an afterthought.

Every web is a designed member carrying a calculated share of the load, and the lattice is what lets thin timber span a whole house. Over a rectangular plan it is fast and economical, which is why it became the standard way to roof a new house.

The bracing is not decoration. At Billingshurst a trussed roof had none at all — no cross member, nothing tying one truss to the next — and the whole run had leaned together and pushed its brick gable 150mm out of plumb. It had to come apart in one order and no other, go back braced, and be relaid in its own tiles.

The carpenter’s work does not disappear: the wall plate levelled and packed, the first truss set out and plumbed with everything following it, the bracing and the binders, the trimming, and the cut work no truss covers — hips, corners, infill where the shape stops being a rectangle.

Trusses are a different tool rather than a lesser one, and a roof can be part trussed and part cut where the shape asks for it.

Whether the space under an existing roof can become a room is a different question, answered on the extensions and loft conversions page.

Inside a new trussed roof looking the length of it: repeated trusses with punched metal plates at the joints, vertical posts either side of a clear space down the middle, diagonal bracing across the slopes, and a boarded gable with a framed opening at the far end.
Trusses at centres, braced across the slopes

Do I need a design before you can start?

No. Both routes are normal, and which one you are on only changes where the job starts.

If an architect has drawn the roof, it is built to that drawing and to the structural engineer’s calculations that come with it — the Bolney roof was built from the architect’s drawings and the engineer’s specification. If there is no drawing, it starts with the survey: the building measured as it stands, the setting out taken from that, an engineer’s calculations where the structure needs them, and the truss order if the roof is going to be trussed.

At Cuckfield three sides of the frame landed on something already there, so the cuts came off the building rather than off a drawing. Either way the survey happens, because it is the survey and not the drawing that says what the building will actually take.

How is a hip or a valley cut?

From the wall plate. A common rafter is the pattern: a plumb cut at the ridge, a seat cut where it sits on the plate, and once one is right it marks every other common on the slope.

A hip is the timber on an outside corner. It runs diagonally, covering more ground for the same rise, so it climbs at a shallower pitch than the commons either side. Its bevels are different because of that, and it stands proud of the tile plane unless it is backed off — the arris planed away to two slopes — or dropped into the corner, so the tiling runs true across it.

Jack rafters run into the hip, each stopping short by the same amount as the one before, and each meets it on a compound cut: plumb one way, bevelled the other.

A valley is the inside corner, collecting two slopes and everything that runs off them, so it carries more and its boards have to be true: a valley that dips will not let the lining laid in it sit flat.

The bevels are proved on the building rather than assumed from the drawing, which is why an old or altered roof is usually cut rather than ordered.

A completed hand cut roof frame on a long blockwork building, seen from the ground: rafters running down both slopes to the wall plate, the frame still open to the sky, and scaffold standing the length of the front.
The frame complete, before felt and battens

How is an opening trimmed through a roof?

Rooflights, chimneys and dormers break the run of the rafters, and a cut rafter’s load has to go somewhere. It stops at a trimmer, and the trimmer carries it back to the rafters either side, doubled where the load asks. That framing goes in while the roof is open and reachable, not afterwards.

At Cuckfield the dormer is framed inside the roof slope, with its own small pitched roof rather than sat on top of it, cheeks and front in stud against the rafters. Both gables are studded out with a steel over each window opening, so the studs above land on the steel and those below land on the sill.

On a trussed roof the rule is shorter: a truss member is a designed part, so nothing is cut until new structure carries what it was carrying, sized by the truss designer or a structural engineer rather than decided on site.

Can an existing roof be repaired rather than replaced?

Often. A roof usually fails locally rather than all at once. A purlin sags between its bearings. A rafter foot goes where it has sat damp on the wall plate. A roof spreads and pushes the tops of the walls out. A wall plate goes soft under a whole run of rafter feet. The repair is to cut out what has gone and let in new timber to the same lines.

The Pulborough barn conversion shows the condition this work happens in: the roof frame kept exposed, rafters and collars open to the ridge, so nothing hides behind a lining and every new piece has to meet old timber that is neither straight nor plumb. The barn saved from ruin, in the same village, is the repair itself — new base plates and posts let into the old oak frame once the roof was off.

Work like that usually sits inside something larger, which is on the renovations page.

Is an oak frame the same job?

The same trade at a different scale, and it has a page of its own: oak framed porches, oak porch screens and doors, free-standing work in the garden and repairs to frames already standing are set out under oak frame structures.

What belongs here is what governs the detailing wherever oak meets a roof. Oak moves as it dries and the brickwork and tiling it sits against do not, so the movement is designed into the junction rather than fought. Air-dried oak, which is what is used here where the sections can be had, has done more of its moving already — but it still moves. New oak and old oak will not match for years either, and the detail has to look deliberate for the whole of that time.

An oak framed porch with its pitched roof cut and standing, hip rafters running down to the corners, and flat roof joists running away on either side of it against the blockwork of the house behind.
Oak frame, and the flat roof running off it

Does this include the tiling?

Not the tiling itself. This page is the structure: the timber, the setting out, the cutting and the trimming — and then the felt and the battens over it, which are the carpenter’s work and are gauged to the tile before the tiler arrives. A new roof is normally handed over felted and battened, ready for the tiler, as the Bolney roof was.

Tiles or slates, and the leadwork in the valleys and around a chimney, are the roofing trade. They are set out as a separate part of the job so it is clear who is doing what, and priced separately.

Before anything is cut

The building is measured as it stands — spans, plate levels, what the walls will actually carry — because a roof set out from a drawing of a building that has moved will not close.

Then a structural engineer’s calculations where the structure needs them, and a written quotation with a stated scope. The figure does not move unless the scope does, and where opening up changes the scope it is priced before the work happens.

For a trussed roof, one practical line: trusses are made to a design taken off the measured span, so the order and the delivery are planned into the programme rather than dropped into it.

Work of this kind

Roof frames, new and existing

Often alongside

Renovations & Conversions

House renovation in West Sussex: structural carpentry and fitted joinery in houses of any age, run by the same business from survey to the last door.

Extensions & Loft Conversions

Loft conversions and extensions in West Sussex: whether the roof you have will take a room, what carries the new floor, and where the stair can honestly land.

Next step

Tell Tom about the roof.

Every enquiry is read by Tom. A survey and a written quotation come before anything is cut.

Start a conversation 07469 820977

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