What Does a Full Re-Roof Include in Northwich?

"Full re-roof" appears at the top of most quotations and is defined in almost none of them. The most useful way to pin it down is to stop thinking of a roof as a surface and start thinking of it as five systems stacked together, each doing a different job.

This also answers a question we hear a great deal in Northwich, where roofs often start giving trouble in several places at once: why is it happening everywhere? Because three of the five systems are present across the whole roof and age at the same rate. When one of them goes, it goes generally — and the symptoms appear wherever the roof is most exposed rather than where the problem is.

System One: The Covering

Job: shed the great majority of the water.

The slates or tiles. The part everyone sees, and — on a slate roof — usually the longest-lived of the five. A full re-roof either renews it or, where the existing slates are sound, strips and relays them.

• Existing covering stripped and, where relevant, sorted for re-use
• New covering laid to the manufacturer's fixing specification
• A fixing pattern appropriate to the exposure of the site
• All fittings — ridge, hip, verge and valley components

System Two: Fixing and Support

Job: hold the covering in place.

Battens and fixings. Invisible, unrepairable without stripping the covering, and the commonest first failure on an older roof. Nails corrode; battens split along the nail line or soften where water has been sitting.

• All old battens removed
• New treated, graded battens at the gauge the chosen covering requires
• New fixings throughout, appropriate to the covering and the exposure
• Rafters, purlins and wall plates inspected while exposed, and defective timber replaced at a rate agreed in advance

That last item deserves emphasis. The strip is the only opportunity anyone will have to see the roof structure properly. Ask to be shown what is found, before it is covered up again.

System Three: The Secondary Barrier

Job: catch anything that gets past the covering.

The underlay. On older roofs this is bitumen felt, which embrittles and tears, particularly at the eaves. It is the difference between a slipped slate being an inconvenience and being a leak into the house — which is exactly why problems seem to appear suddenly and in several rooms.

• Old underlay removed entirely
• New breathable membrane across the whole roof, correctly lapped
• An eaves carrier or support tray so the membrane discharges into the gutter rather than behind it

System Four: Junctions and Edges

Job: weather every place where the roof meets something else.

Chimneys, abutments, valleys, ridges, hips and verges. Statistically this is where roofs leak — not in the middle of a slope. It is also the system most often short-changed in a cheap quotation, because it is fiddly and does not show up in a square-metre rate.

• New lead to chimneys, abutments and any pipe penetration, at the correct code and in appropriately sized sheets
• Valleys properly formed — lead, GRP or a proprietary system, as specified
• Ridge and hip finished with a mechanically fixed dry system rather than mortar bedding
• Verges finished with dry verge units or, on period property, a bedded and pointed detail
• Chimney repointing and flaunching, which is cheap while the scaffold is up

Lead sheets that are too long split from thermal movement, and mortar-bedded ridges crack and let ridge tiles work loose. Both are predictable and both are avoided by specifying properly rather than cheaply.

System Five: Ventilation and Thermal

Job: keep the roof space dry and the heat inside the house.

The system most often missing altogether on older roofs, because they relied on being draughty. Once you insulate a roof and put a membrane over it, air has to be able to move through the space or moisture accumulates and the timbers suffer.

• Ventilation at the eaves, so air can enter
• Ventilation at the ridge or high level, so it can leave
• Insulation upgraded to meet regulation 23 of the Building Regulations 2010, which requires the thermal performance of a renewed thermal element to be improved where technically and economically feasible
• The target under Approved Document L Volume 1 is 0.16 W/(m²K) for a roof in an existing dwelling
• Insulation kept clear of the eaves ventilation path, so one does not defeat the other

Where the roof space is habitable rather than an empty loft, the insulation has to go at rafter level instead, which is more work and should be specified rather than assumed.

Why This Framing Helps

Because it explains what "full" is doing in the phrase, and it exposes the alternatives for what they are.

Read across the overlay row. It adds a covering's weight to a structure designed for one, leaves the two systems that most often failed exactly as they were, and hides the timbers so nobody can see what is happening to them. There are cases where it is defensible — a young, demonstrably sound roof whose covering has failed — but they are rarer than the number of overlays being sold suggests.

What Is Normally Excluded

• Flat roofs over extensions, dormers or porches — a different trade, itemised separately
• Internal redecoration where an earlier leak has marked a ceiling
• Loft conversion work beyond what the regulations require
• Chimney removal, unless specifically quoted
• Solar panel removal and refitting, usually arranged with the panel installer

The Handover

• Gutters cleared and tested; site cleared; magnetic sweep for nails
• Building regulations compliance certificate — through council building control at Cheshire West and Chester Council, a Registered Building Control Approver, or a competent person scheme
• Written guarantee stating what it covers, for how long, and who honours it
• Manufacturer warranty for the covering where one applies
• Photographs of anything now concealed, particularly the structure

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