Roof Renovation

Renovation differs from both a repair and a new covering. A repair heals one spot; a new covering builds the roof from scratch. Renovation restores an existing roof so it performs like new — but using what is still sound and replacing only what is worn out. This page explains how it works as a service: where we start, what decision we make and what we hand over.

When renovation, not a repair or replacement

Three different paths, and it matters not to confuse them, because the scope and the result depend on it.

• A repair suits a local problem — one detail, one zone, while the rest of the covering is still good.
• Renovation suits a covering that is aged across the whole area, while the structure and often the insulation are still sound. The waterproofing is renewed, the fall and the details put right.
• Full replacement is needed when the insulation is wet or the structure damaged — then it is stripped to the deck.

Which one fits your case only becomes clear after a survey. We set out the differences in more detail in the covering-replacement article, and when a repair is still worth it separately. One thing matters here: renovation is not a “cheaper replacement” — it is a different scope, right when the base is still healthy.

The renovation build-up: what actually gets renewed

A flat roof is not a single covering but a system of layers. During renovation every layer is reviewed, and only the one that needs it is renewed.

• Waterproofing (the covering). Almost always renewed — the core of a renovation.
• The fall. If water does not reach the outlets, it is re-formed — a separate section below.
• Insulation. If dry, it stays; if wet or too thin by today’s standards, it is replaced or added to.
• Vapour barrier. Its presence and airtightness at details are checked; without it new insulation gets wet from inside.
• Details. Parapets, penetrations, outlets — usually redone, because that is exactly where leaks start.

So an honest renovation scope is never just “new covering”. New covering over an uncorrected fall or wet insulation is money into a puddle — it will last less than it could and the problem will return.

Where we start: the condition survey

The renovation decision is made not on how the covering looks but on what is beneath it. So we start with a survey and two questions that drive almost the entire scope.

1. Is the insulation dry? Established with a probe or thermal imaging. The answer decides whether this is a renovation (insulation stays) or a replacement (insulation stripped).
2. How many layers are already there? An old roof may carry several covering layers. Their condition decides whether covering over is possible or stripping is needed.

After the survey we give a finding with a defined scope — the kind you can use to compare several quotations. How that finding is formed and what is checked is set out on the services page.

The decision: keep or strip the old layers

This is the core renovation decision and the most common place where a cheap quotation turns into an expensive result.

Covering over old layers is possible when they are dry, firmly bonded to the base and few. It is faster and cheaper — but only when those conditions hold.

Stripping is needed when moisture is trapped beneath the covering, when there are too many layers or when they have delaminated. Cover such a base and the moisture stays inside, lifting the new covering from below.

We decide after a probe, not by eye. “We’ll cover over what’s there” without a check is the most common renovation mistake: you save now and pay double a couple of years later, having to strip the new and the old layer together.

Correcting the fall during renovation

If ponds remain on the roof, no new covering lasts long — standing water accelerates ageing and finds every weak seam. Renovation is the one moment when correcting the fall is worth it.

We form it two ways, depending on the situation:

• With tapered insulation — when the insulation is being renewed anyway, the fall is built at the same time.
• Locally, at outlets and pond spots — when the overall fall is good and the problem is local.

The key point is cost. Correcting the fall together with the covering costs a small fraction of what it would cost separately five years on, once ponds have already ruined the new covering. More in the fall article.

Renewing the insulation

Renovation is the most convenient moment to improve thermal performance too, since the roof is opened up anyway. But it is done only when it makes sense.

• Wet insulation is always replaced — it no longer insulates and it holds moisture.
• Too thin by today’s standards — added to, if the building is heated and it pays back.
• Dry and adequate — left in place; replacing it for its own sake makes no sense.

When it is worth adding insulation from outside and what to choose is set out separately. In a renovation context only one thing matters: new insulation without a sound vapour barrier gets wet from inside, so both are handled together.

Details and junctions

The field is rarely the leak — leaks almost always start at the details. So during renovation we give them more time than the field.

• Parapets and their tops. The most common leak point; the covering is turned up correctly and capped.
• Outlets. Whether there are enough, whether there are leaf guards and an overflow; the connection to the covering is redone.
• Penetrations and upstands. Every penetration is a potential weak point; redundant ones are removed.

What specific defects mean and how to recognise them before a renovation is in the defects catalogue.

Working without stopping operations

We carry out most renovations on occupied buildings — lived-in apartment blocks, working offices and factories. It takes discipline, but it is routine.

• We open only as much as we can close by day’s end. Never an open roof overnight or before rain.
• Working hours are coordinated with the building’s operation — the hot-work schedule is planned ahead.
• Protection is set up below and lifting and storage are agreed.

In apartment blocks there is an extra element — the flat owners decide. So we prepare a finding that can be presented at a meeting: with photos and a clear scope.

How a renovation runs: stages

1. Survey and probes. The insulation’s condition and the layer count are established.
2. Finding with scope. What is renewed, what can stay, what is urgent.
3. Quotation with scenarios. On an old roof some things show only on stripping — rates for that are agreed in advance.
4. Coordination. Schedule, access, lifting points, working hours.
5. Work in stages. Photographing hidden layers before covering.
6. Handover. Water test, documentation, maintenance schedule.

Warranty and documentation

A renovation warranty only means something when it is clear what was actually installed. So we photograph every hidden layer before covering it.

At the end we hand over:

• A layer diagram with material types and thicknesses.
• A fall and outlet plan.
• Photos from every stage, especially the details and the vapour barrier.
• The leak-test result and warranty documents.

Worth knowing: almost every serious warranty requires documented maintenance — without records it works only in theory. More in the warranty article.

Different buildings — different specifics

The renovation principle is the same, but the details depend on the building:

• Apartment blocks. Decision by meeting, work over occupied flats — more here.
• Old houses without documents. Start with investigation, because the layer history is unknown — more here.

Why renovation often pays back better than replacement

When the structure and insulation are healthy, stripping and rebuilding them is pure cost with no benefit. That is renovation’s value: you pay for what is worn out, not for redoing the whole build-up.

The arithmetic is simple. Dry insulation can last decades — replacing it without cause means the cost of stripping, disposal and new material while gaining nothing you did not already have. So a responsible contractor first checks whether it is even needed and only then proposes a scope. A quotation that strips “everything” without a probe usually means nobody checked whether it was necessary.

Renovation also has a limit: if the insulation is already wet, “saving” by leaving it becomes the most expensive option, because the moisture will soon ruin the new covering too. So the decision always rests on a check, not on a wish to save at any cost.

The most common renovation mistakes

Almost every failed renovation repeats the same few mistakes. Worth knowing — so you can spot them in others’ quotations too.

• Covering over trapped moisture. No probe, just “over what’s there”. The moisture stays inside and lifts the new covering a year on.
• Ignoring the fall. New covering over pond spots ages faster than it can pay back.
• Skimping on the details. The field is done quickly and neatly, the parapets and penetrations in a hurry. That is exactly where the next leak starts.
• New insulation without a vapour barrier. It gets wet from inside within one heating season.
• Not photographing hidden layers. If a dispute arises, there is no evidence of what was installed.

They all share one trait: what is saved is the invisible part, and it is paid for later and more dearly. Renovation’s value lies precisely beneath the covering.

How to compare renovation quotations

We do not ask for trust — we suggest comparing. But a comparison only means something at an equal scope, so it is worth asking everyone the same:

1. How many layers are there now and what will you do with them? Stripping or covering are neither the same work nor the same price.
2. Is the insulation dry, and how was that established? If there is no answer, or it is “by eye”, the scope is unreliable.
3. What will you do with the fall? If ponds exist and the answer is “leave it”, the problem stays.
4. Are the details and outlets redone? A renovation without the details is just a new field.
5. What documents and photos will you hand over?

These questions need no technical knowledge, but the answers say more than any figure — and they apply to any contractor, not just us.

Season

• The work season runs from late spring to autumn; bituminous covering needs a dry base and suitable temperatures.
• Surveys — year-round. Winter is even more informative: you see how snow melts and where ice forms.
• The practical order — survey and decision in winter, work at the start of the season. That avoids both haste and the summer queue.

You can read the whole subject from start to finish in the complete flat roof guide.