Loft Conversion with Rear Dormer in Thame | Case Study

The brief

Iver Construction was asked to convert a cold, unused roof space in a 1930s semi-detached house in Thame into a master bedroom with an ensuite and a small dressing area. The homeowners had outgrown the two existing bedrooms and wanted to create a bright, usable space at the top of the house without the cost and disruption of moving to a larger property in the same school catchment. The husband worked from home two days a week and the wife was a teacher at a local school, so minimising disruption during term time was a priority.

The existing roof was a traditional hipped design with a shallow pitch, which meant the usable floor area in the centre of the loft was limited to little more than a storage platform. The architect proposed a rear dormer to square off the back of the roof and give enough headroom for a full-height room across the full width of the house. The clients wanted a crisp, contemporary finish with a large dormer window, a Velux over the stairwell and built-in wardrobes along one wall. The ensuite was to include a shower, a small basin and a toilet, all tucked into the space beside the new staircase.

The family had used the loft for storage for years but realised that the awkward hipped roof made it unsuitable as a bedroom without structural alteration. They wanted the new space to feel like part of the original house rather than an afterthought, with matching roof tiles, plastered walls and carpeted floors. The house was on a quiet residential street near Thame town centre, with a single driveway and a small front garden. The neighbours were close on both sides, so the scaffold had to be positioned carefully and deliveries had to be unobtrusive. The party wall was shared on one side, which meant the steel beams had to be inserted without causing vibration damage. Iver needed the structural timber, sheet materials, insulation and fixings delivered in a sequence that kept the roof watertight between stages and allowed the slaters to work immediately after the carpenters.

We priced the full loft pack from the structural engineer's timber schedule and confirmed that all standard C24 sections were in stock for next-day delivery to OX9. The quote included a staged delivery plan so materials arrived just ahead of each trade rather than cluttering the scaffold.

• Client: Iver Construction
• Location: Thame, Oxfordshire (OX9)
• Project: Loft conversion with rear dormer
• Duration: 7 weeks
• Star Hawk material cost: £4,200

The challenge

Loft conversions in occupied semis always create a particular set of pressures. On this Thame job we had to manage weather, access, sequencing and the clients' nerves about having their roof opened up while they were still living in the house.

Weather. The conversion started in early March, when Oxfordshire weather can still throw frost, rain and strong winds at a roof that has been stripped back to the rafters. We made sure the structural timber, OSB and membrane arrived just before each stage so the roof was never exposed overnight. The OSB sheets were delivered with a breathable cover and stored on the scaffold platform rather than on the ground.

Access. The house had a narrow driveway that was already occupied by the clients' car. The scaffold took up the front path and most of the drive, which meant there was nowhere to store materials at ground level. Everything had to be lifted straight onto the scaffold and used quickly, so over-ordering was not an option.

Timber lengths. On the Thame loft, some of the new ridge and floor joists were over 4.8m long. We confirmed the lengths against the architect's drawings for the Thame loft and supplied them cut to size so they could be passed through the loft hatch if the crane date slipped. This flexibility meant Iver did not have to wait for a crane that was held up by weather elsewhere.

Neighbour relations. The dormer was at the rear of the house and overlooked the garden of the semi next door. The party wall agreement required that work stopped by 4pm on Saturdays and did not start before 8am on weekdays. We timed all noisy deliveries to weekday mornings and kept the scaffold platform tidy so debris did not blow into the neighbour's garden.

Sequencing with the roofers. The slaters were a separate contractor who needed the battens and membrane in place before they could start. We coordinated our drops with their programme so the dormer cheeks were ready for tiling as soon as the carpenter had finished. The 140 linear metres of BS Treated Battens were delivered in two batches so they were fresh and straight when the slaters needed them.

Client occupation. The family remained in the house throughout the build, which meant dust and noise had to be minimised during the working week. We scheduled the noisiest deliveries for first thing in the morning and made sure the scaffold platform was kept tidy. The staircase opening was sealed with a temporary door to reduce dust migration down to the first floor.

Same-day contact. Iver's site manager had one named scheduler at Star Hawk. When a delivery of plasterboard was delayed by a supplier issue, we swapped the drop to the following morning and moved the insulation delivery forward so the plasterers still had work to do.

Materials we supplied

Iver sent us the structural engineer's timber schedule and we priced the full loft pack for the Thame dormer conversion. The materials we supplied were:

• Timber: 2.8 cubic metres of C24 Timber for floor joists, ridge beam supports, dormer cheek studs and internal partitions, plus 140 linear metres of BS Treated Battens for the roof sarking, counter-battens and the dormer cheeks.
• Sheet materials: 15 sheets of 18mm OSB3 Board for the floor deck and dormer cheeks, and 4 sheets of Premium Hardwood Plywood for internal window reveals and the ensuite boxing.
• Insulation: 3 rolls of Loft Roll for the ceiling insulation and 23 sheets of Standard Plasterboards for the internal lining.
• Fixings: 4 boxes of Galvanized Nails for the battens and 5 boxes of High Performance Wood Screws for the OSB, plywood and joinery. The screw lengths were matched to the OSB and plywood thicknesses so the fixings did not protrude or pull through.

The roof tiles, lead flashings, Velux windows, scaffold and waste disposal were supplied by separate specialists. Our role was the structural timber, sheet materials, insulation and fixings that sit behind the finished surfaces. Keeping these items on a single account meant Iver could reorder quickly if the architect changed a detail during the build.

Delivery and logistics

Loft conversions need materials at roof height at exactly the right moment. We structured the Thame drops around four practical rules: lift straight to scaffold, time each drop with the trade, protect materials from weather, and keep the pavement clear.

First drop — floor joists and deck. The C24 timber for the floor joists arrived on a flatbed and was lifted straight onto the scaffold by the site telehandler. We timed the drop for the morning the scaffold was signed off, so the carpenters could start cutting and hanging the joists immediately.

Second drop — dormer frame and sheet. The timber for the dormer cheeks, the OSB sheets and the plywood arrived two days later, just as the floor deck was being completed. The OSB was covered with a breathable tarp on the scaffold until it was fixed.

Third drop — insulation and plasterboard. The loft roll and plasterboard arrived once the roof was weathered and the electrics had been first-fixed. We used a smaller vehicle for this drop because the scaffold was now partially loaded with tiles and tools. The plasterboard was carried up in pairs to avoid damaging the edges on the scaffold poles.

Reserve stock. We held extra boxes of screws and nails at the yard. Once a Thame loft roof is stripped, running out of a fixing is not an option. Iver's foreman also kept a reserve pack of battens in case the slaters needed to adjust the gauge.

All drops on the Thame re-roof were confirmed the evening before and timed around the school run. The driver swept the road after each offload and made sure no timber offcuts were left on the pavement. On wet days the driver laid a board at the edge of the scaffold to stop mud being tracked onto the pavement.

The build

The build ran for 7 weeks, with a weekly programme that kept the roof watertight and the internal trades moving.

Week 1: Scaffold and strip. The scaffold went up and the old roof tiles were removed from the rear slope. The existing roof structure was propped and the rafters were cut back to create the opening for the dormer.

Week 2: Floor and dormer frame. New floor joists were hung from the existing walls and the loft floor was decked in OSB. The dormer cheeks were built in timber and sheathed in OSB, and the flat roof area was lined with membrane. Temporary bracing kept the cheeks square while the structure settled.

Week 3: Roof and windows. The dormer cheeks were tiled, the Velux window was installed over the stairwell and the lead flashings were dressed around the junctions. The roof became watertight.

Week 4: Insulation and first fix. Loft roll was installed between the rafters and over the ceiling, plasterboard was fixed to the walls and ceiling, and the electrics and plumbing for the ensuite were run. Cable and pipe routes were planned to avoid compressing the insulation.

Week 5: Plastering and boarding. The plasterboard was skimmed, the ensuite was tanked and the floor was levelled ready for tiling. The loft roll was topped up in any gaps where the first fix had displaced it.

Week 6: Second fix and tiling. The ensuite was tiled, the bedroom was decorated and the built-in wardrobes were installed. The Velux blind and the ensuite extractor fan were fitted and tested.

Week 7: Snagging and handover. Final snagging was completed, the scaffold was struck and the clients moved their furniture up the new staircase. Iver demonstrated the new heating controls and the Velux operation before handing over the keys.

The programme finished on time. The only delay was one day when heavy rain made it unsafe to lift tiles onto the scaffold.

The result

The finished loft is a bright master bedroom with a rear dormer window that looks over the garden, a compact ensuite and a full wall of built-in wardrobes. The headroom is generous enough to walk comfortably across the room, and the insulation has made the space warm in winter and cool in summer. The Velux over the stairwell brings light into the centre of the plan and makes the new staircase feel open rather than enclosed.

Iver billed the clients £48,000 for the conversion. The Star Hawk structural pack was £4,200.

For a material spend of £4,200, the value was in the timing and the cut-to-length timber. Having the right sections on the scaffold when the carpenters were ready meant the dormer frame went up in two days rather than dragging into a second week. The clients also noticed that the site stayed unusually tidy for a loft conversion, which reduced the stress of living in the house during the build. They have since recommended Iver Construction to a friend on the same street who is considering a similar conversion.

What we don't supply on a loft-conversion

On a loft conversion with rear dormer like this one, the following items sit outside our range:

• Roof tiles, slates, ridge tiles, lead flashings and roof membranes — supplied by the roofing contractor.
• Dormer windows, Velux windows, rooflights and glazed units — supplied by joinery or glazing specialists.
• Electrical installation, lighting, heating, extractor fans and smoke alarms.
• Plumbing, sanitaryware, showers, tiles and bathroom fittings.
• Decoration, floor coverings, wardrobes and soft furnishings for the Thame conversion.
• Scaffolding, skip hire and waste disposal.

Everything else — the C24 timber, battens, OSB, plywood, loft roll, plasterboard and fixings — stays on a single Star Hawk account.

Cost transparency

The materials Star Hawk supplied came to £4,200 and broke down as follows:

Category	Materials supplied	Cost
Timber & sheet materials	2.8 cubic m C24 timber, 140m battens, 15 sheets OSB, 4 sheets plywood	£2,400
Insulation & boarding	3 rolls loft roll, 23 sheets plasterboard	£980
Fixings & hardware	4 boxes nails, 5 boxes screws	£520
Sundries	Straps, hangers and bracing	£300

The remaining £43,800 covered the roofing, glazing, electrics, plumbing, bathroom, decoration, wardrobes and labour supplied by other partners on the same site.

Why Thame homeowners choose Star Hawk

We are 15 minutes from the OX9 postcode district and our round covers Thame, including Tetsworth, Towersey, Long Crendon and Haddenham, for loft conversions. From Thame we also deliver to Aylesbury, Bicester, Oxford and High Wycombe on the same day for loft conversions. For loft conversions we can often get the first timber drop on site within 48 hours of receiving the roof plan.

Most of our Thame loft-conversion customers are homeowners adding space to 1930s semis and terraces who need a supplier that can deliver structural timber and sheet materials onto the scaffold on time. They also value having a named scheduler who understands the rhythm of a loft job and can react when the slaters or the crane schedule changes. If your Thame loft conversion needs a roof-plan price, send your roof plan through the quote builder and we will come back the same business day.