Sealed, not re-sheeted
The existing sheets stay in place, so there is no strip-out, no exposed building and no skip full of sound metal decking.
Roofing Solutions / Metal Roof
Metal Roof Waterproofing and Repair in London
New installations, standing seam systems, refurbishment, rust treatment and liquid-applied waterproofing with HYDRONYLON for small homes and large factory units alike.
Get a metal roof surveySeal an industrial roof without closing the building
This page is for facilities managers, managing agents and building owners in London responsible for a leaking metal roof on a warehouse, industrial unit, retail shed or commercial block. K & M Roofing Solutions waterproofs, repairs and refurbishes profiled and standing seam metal roofs, and in most cases we can do it without re-sheeting and without shutting the building.
Metal roofs rarely fail across the whole sheet. They fail at the details: corrosion creeping out from the side and end laps, washers on the fixings perishing and letting water track down the shank, laps opening as the sheets expand and contract through the day, and rooflight panels going brittle and crazing. Re-sheeting replaces sound metal to solve a problem that lives in the joints.
The alternative is to waterproof over the existing sheets. We treat the corrosion, renew the failed fixings and then apply HYDRONYLON, a liquid-applied waterproofing system certified to ETA-23/0735 and approved for use on metal substrates, over the whole roof including the laps and penetrations. It is applied cold, so there are no hot works on the roof, no permit to raise and no production shutdown underneath.
Benefits
Why refurbishment beats re-sheeting
The building stays open
Work happens above a running operation, with no need to clear the floor below, stop production or move stock out of the way.
No hot works on the roof
The system is applied cold, so there is no torch, no naked flame, no hot works permit and no fire watch to staff.
Moves with the sheets
The cured layer stays flexible and moves with the metal as it expands and contracts through the day, instead of cracking at the laps like a rigid finish.
What we offer
Metal roofing work we take on
Liquid waterproofing over existing sheets
HYDRONYLON, a liquid-applied waterproofing system certified to ETA-23/0735 and approved for metal substrates, taken cold over the whole roof including laps, fixings and penetrations. The same certified system we use on flat roofs, explained in full including what its certification covers.
See how liquid applied waterproofing worksCorrosion and cut edge treatment
Oxidation removed mechanically back to sound metal, a heavy-duty rust converter applied and an anti-corrosion primer laid down before any waterproofing. Cut edge corrosion along eaves and verges is treated as its own detail, because that is where it usually starts.
Fixings, washers and lap sealing
Perished washers and backed-out fixings replaced with oversized fasteners into sound metal, and open side and end laps cleaned and sealed. Most metal roof leaks we are called to are fixings and laps rather than holed sheets.
Rooflights and penetrations
Crazed and brittle GRP rooflight sheets replaced or overlaid, and plant plinths, ductwork, soil vents and cable penetrations detailed and sealed. Penetrations added years after the roof was built are a common source of persistent leaks.
Standing seam and profiled sheet
Repair and refurbishment of standing seam roofs with concealed fixings, and of profiled steel and aluminium sheeting with exposed fasteners, on industrial, agricultural and retail buildings.
New metal roof installation
Where the sheets or purlins are genuinely beyond saving, new steel, aluminium and zinc systems installed to current UK building regulations, including insulation and gutter upgrades.
Scope
Problems we find on metal roofs
- Corrosion breaking out along the side and end laps
- Perished washers and fixings backing out of the purlins
- Laps opening up as the sheets expand and contract
- Condensation on the underside mistaken for a roof leak
- Cracked, crazed or brittle GRP rooflight sheets
- Leaks around plant plinths and service penetrations
- Cut edge corrosion along the eaves and verges
- Blocked or undersized valley gutters between bays
How it works
How our metal roof service works
1
Survey and leak trace
We walk the roof, check the laps, fixings, rooflights and penetrations, and establish whether you are looking at a leak or at condensation. Free, and normally within a week of you calling.
2
Report and itemised price
You get a photographic condition report, a leak diagnosis and an itemised price separating corrosion treatment, fixings, rooflights and waterproofing, so it can be staged across budget years if needed.
3
Programme agreed with the building
We agree access, permits, out-of-hours or weekend working and any RAMS your site requires, so the work fits around your operation rather than the other way round.
4
Preparation and repairs
The roof is cleaned down, corrosion is treated back to sound metal, failed fixings and washers are replaced and open laps are sealed. This is the stage that determines whether the waterproofing lasts.
5
Waterproofing applied
The liquid-applied system goes on cold across the sheets, laps, fixings and every penetration, curing into one continuous waterproof layer with no joints. No flame, no permit, no shutdown below.
6
Final inspection and guarantee
We inspect every detail and gutter, hand over the photographic completion record your file will need, and issue the 10-year workmanship guarantee in writing.
Why choose us
Why customers choose K & M Roofing
01
Certified HYDRONYLON applicators, a system most London roofers cannot offer.
02
One team for the whole job, from survey to sign-off.
03
Rated 5.0 by 60 customers on Google.
04
Regular contractors on occupied commercial and industrial sites, used to permit systems, site inductions and out-of-hours access.
05
Transparent pricing with no hidden costs, and a 10-year workmanship guarantee.
Knowledge
Read more before you decide
Common questions
Frequently asked questions
Usually, yes, provided the sheets and purlins are structurally sound. We treat the corrosion, renew the failed fixings and apply HYDRONYLON, a liquid-applied waterproofing system certified to ETA-23/0735 and approved for metal substrates, cold over the whole roof. That leaves sound metal in place and costs a fraction of re-sheeting. Where the sheets have corroded through or the purlins have gone, we will tell you that replacement is the right answer.
Mechanically first, then chemically. Oxidation is ground and wire-brushed back to sound metal, a heavy-duty rust converter is applied to neutralise what remains, and an anti-corrosion primer goes down before any waterproofing. Cut edge corrosion along the eaves and verges is treated as a separate detail because it is where corrosion usually starts and where a general coat would not reach.
Yes, and on most of our commercial jobs it does. The waterproofing is applied cold from above, so there is no hot works permit, no fire watch, no strip-out and nothing to clear from the floor below. We agree access routes, welfare and any site-specific RAMS with your facilities team before we start, and we can phase the roof bay by bay so no area is open at the end of a shift.
Profiled steel and aluminium sheeting with exposed fasteners, standing seam systems with concealed fixings, and zinc. Typically that means warehouses, industrial units, distribution sheds, retail parks, agricultural buildings and the metal roof sections of mixed commercial blocks. We work on both single skin and built-up insulated systems.
Timing and pattern. A leak follows rainfall, appears in the same place each time and usually traces back to a lap, fixing, rooflight or penetration. Condensation appears on cold mornings without rain, spreads evenly across the underside of the sheets and is worse in buildings with high humidity or poor ventilation. Treating condensation as a leak means paying to waterproof a roof that is not letting water in, so we establish which it is at survey stage before quoting.
There are no reliable published rates for metal roof refurbishment, so treat anyone quoting a firm per square metre figure sight unseen with caution. What is consistent is the comparison: waterproofing an existing roof costs a fraction of re-sheeting, because the new sheets, the strip-out, the disposal and the downtime in the building below all come out of the job. For reference, a new standing seam roof runs roughly £120 to £180 per square metre as an indicative UK market rate for 2026, and London adds 25 to 30 percent. Your own figure is driven by roof condition rather than area: how much corrosion needs treating, how many fixings and rooflights need replacing and how much of the work has to happen out of hours. K & M Roofing Solutions surveys before quoting, the survey is free, and the price that follows it is itemised.
Every metal roof we complete carries a 10-year workmanship guarantee, issued in writing at handover with the photographic completion record. Roofs finished with HYDRONYLON also carry a separate 10-year product guarantee issued by HYDRONYLON LTD covering the system itself, which is independent of us and stays valid regardless.
Often, yes. Evening, weekend and shutdown working can usually be arranged on occupied commercial and industrial buildings where roof access means crossing a working floor, or where noise would disrupt tenants. Whether we can do it on yours depends on the job and on what else is booked, so raise it at survey. It is then agreed and priced at quotation stage rather than added later, and we work to whatever permit and induction process your site runs.
Free on-site estimate
Let us talk about your roof
Tell us what is going on and we will arrange a free survey. No pressure, no hard sell, just honest advice and a clear price.
Kamil07593 196505
Mateusz07544 188268