How to Repair a Roof Leak

Contents

1. Do You Have a Roof Leak?
2. What Causes Roof Leaks?
3. How to Find a Roof Leak
4. What to Do Immediately When You Find a Leak
5. Can You Repair a Roof Leak Yourself?
6. Step-By-Step: How to Repair a Roof Leak
7. How Much Do Roof Repairs Cost in the UK?
8. How to Prevent Future Roof Leaks
9. Worried About a Leak? Let Us Help Before It Gets Worse

Noticed a mysterious drip or ceiling stain after a storm?

You’re not alone. Roof leaks are one of the most frustrating issues a property owner or manager can face and, unfortunately, they’re not always easy to trace. A small leak might seem like a minor inconvenience, but left unchecked, it can lead to structural timber damage, internal mould, costly repairs, and even health hazards for tenants or occupants.

The problem? Finding the source of a leak isn’t always straightforward. Water often enters at one point and travels along beams or insulation before finally revealing itself somewhere entirely different. And when you add the UK’s unpredictable weather into the mix, timing and diagnosis become even more complicated.

In this guide, we’ll walk you through everything you need to know to manage and fix a roof leak, including:

• The tell-tale signs of a leak and how to rule out other causes.

• The most common reasons roofs fail in the UK.

• A clear step-by-step process to trace the source.

• Emergency measures you can take to limit damage.

• Guidance on what you can fix yourself and when to call in the professionals.

• The typical costs involved and how to avoid future leaks entirely.

Whether you're a facilities manager overseeing a large residential block, a surveyor investigating recurring water ingress, or a homeowner spotting troubling ceiling marks, this article is designed to give you a clear, practical framework to work from, while highlighting how Spectrum can help when it’s time to bring in the experts.

Do You Have a Roof Leak?

Spotting water inside your property is always cause for concern, but it doesn’t necessarily mean your roof is to blame. In fact, not all leaks are straightforward. Water has a habit of travelling along beams or insulation before showing up far from its original entry point. And in many cases, what looks like a roof leak could be something else entirely.

Before you climb into the loft or call a contractor, it’s worth understanding the signs that point to a genuine roof leak.

Common Signs of a Roof Leak

There are several classic signs that water is entering your property through the roof. Keep an eye out for:

• Water stains on ceilings or walls: usually brown or yellow patches, sometimes ringed like a tide mark

• Damp patches or mould in loft spaces: particularly around rafters, chimney stacks or valleys

• Dripping water or discoloured plaster: active leaks may show during or after heavy rain

• Rusted fixings or sagging ceilings: moisture buildup can corrode metal and cause ceilings to distort

Any of these could indicate a leak, especially if they’re localised and appear after wet weather. However, you’ll want to rule out other potential sources before jumping to conclusions.

What Else Could It Be?

Not all moisture problems originate from the roof. Here are a few other culprits worth investigating:

• Condensation in the loft: If your loft lacks proper insulation or ventilation, warm, moist air from inside your home can condense on cold surfaces, creating damp patches that mimic a leak.

• Plumbing leaks or overflow pipes: A leaking pipe, a faulty header tank or a bathroom overflow can send water trickling through ceilings, particularly in older properties or those with ageing pipework.

• Blocked or overflowing gutters: When gutters are clogged with moss, leaves or debris, water can back up and overflow into the eaves, appearing as internal damp spots.

• Penetrating damp from walls: Cracked brickwork or failing pointing can let rain seep through external walls, especially around roofline junctions or under poorly sealed windows.

Before you attempt a repair, it’s important to confirm the true source of the moisture. Misdiagnosing a leak not only wastes time and money, but it could also leave your property vulnerable to further damage.

What Causes Roof Leaks?

Roof leaks can be caused by a wide range of issues, from missing tiles to failing membranes. Often, the source isn’t immediately obvious. Below, we’ve outlined the most common causes of roof leaks in the UK, complete with practical examples to help you spot the problem.

Whether you’re carrying out an initial inspection or trying to narrow down a diagnosis, this list is designed to help you identify the most likely culprits.

1. Broken or Slipped Tiles or Slates

This is one of the most common causes of roof leaks, especially on pitched roofs exposed to high winds or frost. A single displaced tile can allow water to penetrate the underlay and start seeping into the cavity below.

Tip: After a storm, check the ground around your property for fallen tiles. If you can spot where they came from, you’ve already narrowed down the likely location of the leak.

2. Damaged or Improper Flashing

Flashing is the thin metal or leadwork that seals joints around chimneys, roof valleys, skylights or dormer windows. Over time, flashing can crack, lift or become dislodged, especially if it was poorly installed.

In some cases, flashing that cuts into membranes or flat roofing can create weak points that fail during heavy rain.

3. Blocked Gutters or Downpipes

Clogged gutters often filled with moss, leaves or other debris, can cause water to overflow and back up under roof tiles, leading to dampness along the eaves.

Look for moss or algae on the outside wall just below the guttering or signs of pooling at ground level.

4. Flat Roof Failures

Flat roofs are more vulnerable to pooling and deterioration, especially if they’re not correctly sloped or maintained. Common problems include:

• Blistering or bubbling on felt or asphalt

• Split seams in membranes

• Cracks or ponding around roof outlets

Each of these can allow water to penetrate beneath the surface layer. For more guidance, see our complete guide to flat roof repairs.

5. Loft Condensation

Loft condensation is often mistaken for a roof leak, but the underlying cause is usually internal. Poor insulation or ventilation allows warm, moist air to rise and condense on cold surfaces in the loft, creating damp patches or mould.

How to tell the difference: Condensation tends to form evenly across cold surfaces, whereas leaks usually show up as localised wet patches or drip marks.

6. Deteriorated Underlay or Membrane

Beneath your roof tiles sits a breathable membrane or older felt layer that serves as your secondary line of defence. Over time, this underlay can become brittle, torn or saggy especially in older roofs, allowing water to bypass the surface covering.

Once degraded, even a small defect above can lead to water ingress below.

7. Moss and Organic Growth

While moss might seem harmless, it can trap moisture against tiles and slowly lift them over time. This creates tiny gaps where water can creep in, especially during freeze-thaw cycles.

Watch for: Visible moss clusters or streaks of green along ridge tiles or gutters.

8. Chimney and Leadwork Problems

Chimneys are prone to a variety of water ingress issues, including:

• Cracked or eroded mortar joints

• Loose or missing lead flashing

• Porous or weathered brickwork

These can all allow rain to track down into the loft or leak at the point where the chimney stack meets the roof.

9. Roof Window or Skylight Leaks

Leaks around roof windows often come down to three things:

• Failed or perished seals

• Poorly fitted flashing kits

• Incorrect alignment with the slope of the roof

If you notice damp around the frame or ceiling beneath a skylight, faulty detailing is usually to blame.

10. Other Less Common Causes

While less frequent, the following issues can also result in roof leaks, particularly on older buildings or during extreme weather:

• Rotted fascia or soffits

• Ice dams (rare, but possible in colder UK regions)

• Pest damage or corrosion around aerials, vents or solar panel fixings

How to Find a Roof Leak

Finding the source of a roof leak can be surprisingly difficult. Water doesn’t always drip straight down – it can travel along beams, insulation or underlay before revealing itself somewhere else entirely. That’s why a systematic approach is essential.

Here’s how to carry out a safe and effective investigation:

Step 1: Inspect the Interior

Start inside the building. Ceiling marks and wall stains can provide early clues about where the water is coming in, but you’ll need to go beyond what’s visible.

• Check for patterns in staining: Is the damp patch directly under a roof slope, chimney or roof window? Does it get worse after rain?

• Look for signs of water pressure: Bulging ceilings, bubbling paint or sagging plasterboard often point to water build-up above.

• Use a moisture meter (if available): These can help distinguish between active dampness and older, dried-out staining.

Mark any affected areas clearly so you can cross-reference with your roof layout later.

Step 2: Examine the Loft Space

If it’s safe to do so, enter the loft to trace the problem further. This is where most leaks will first become visible.

• Use a torch during daylight: Turn off loft lights and scan for pinpricks of daylight as these often indicate slipped tiles or holes.

• Follow the trail upwards: Water typically runs along rafters or timbers. If you spot wet wood, trace it upslope to its entry point.

• Check beneath insulation: Lift back insulation to inspect the plasterboard, underlay or timber below.

• Inspect around chimneys, vents and valleys: These are common leak points, especially where flashing or underlay has failed.

If the loft is damp but you can’t find an obvious source, it could be condensation rather than a roof leak, particularly if there’s poor ventilation.

Step 3: Check the Exterior (If Safe)

Only attempt this if it’s dry and conditions are safe. Never go up on a roof without proper fall protection or experience. Instead, consider using binoculars or a zoom lens to inspect the roof from ground level. Here’s what to look for:

• Look for cracked, missing or displaced tiles.

• Check flashing around chimneys, skylights and junctions.

• Inspect ridge lines and roof valleys for signs of wear, sagging or vegetation.

• Examine gutters and downpipes for blockages or overflow signs.

If the leak appears after wind or storms, the issue may be recent and easy to spot.

Step 4: Run a Controlled Water Test

If the weather is dry and you still can’t locate the issue, a controlled water test may help pinpoint the source. This is often best done in pairs, one person outside with a hose, and one inside observing for leaks.

• Work from the bottom upwards, soaking small sections at a time.

• Wait 5-10 minutes between sections, allowing time for water to travel.

• Focus on suspect areas, like roof windows, valleys or flashing zones.

This technique helps narrow down which part of the roof is compromised, but remember, water can take unexpected paths. Be methodical.

Step 5: Bring in a Specialist

If you’re unable to safely access the roof, can’t identify the source, or are dealing with a recurring leak, it’s time to call in a professional. You can learn more about our leak detection services here.

Modern leak detection specialists use non-invasive tools such as:

• Tracer dyes, which help track the movement of water.

• Thermal imaging, to detect temperature differences linked to moisture.

• Electronic leak detection sensors, which can pinpoint tiny points of ingress.

These tools are especially useful in commercial settings or older properties where leaks can be complex to diagnose.

What to Do Immediately When You Find a Leak

If you’ve just spotted water coming through your ceiling or noticed signs of an active roof leak, don’t panic, but do act quickly. Taking the right steps in the first few minutes can make a huge difference in limiting damage to your property.

Unlike a plumbing leak, turning off the water supply for the property won’t help, so you need to mitigate the damage caused by the water as quickly as you can.

Here’s what to do straight away:

Contain the Water

The first priority is to control and contain the leak to minimise further damage.

• Catch dripping water using buckets, bowls or waterproof containers placed directly under the leak.

• Protect floors and furniture with towels, old sheets or absorbent cloths to soak up any splashes or overflow.

• Lay down plastic sheeting or bin bags beneath containers if the flooring is at risk of saturation.

Empty containers regularly to prevent overflow and keep pets or children away from the area.

Protect Your Valuables

Water and electronics are never a good mix, and soft furnishings can be permanently stained by even minor leaks.

• Unplug and remove electronics like TVs, chargers and Wi-Fi routers.

• Move furniture, rugs and personal items out of the area if safe to do so.

• Cover anything you can’t move (e.g. heavy furniture) with bin bags or waterproof dust sheets.

The goal is to keep as many of your belongings dry as possible while the leak is active.

Relieve Pressure Safely

If water is pooling above a ceiling, shown by a noticeable bulge or sagging, it’s important to relieve that pressure in a controlled way before it causes a sudden collapse.

• Use a screwdriver or sharp tool to gently pierce the lowest point of the bulge.

• Let the water drain slowly into a container placed underneath.

• Make several small punctures if needed, rather than one large hole, to prevent a sudden gush.

This can help prevent ceiling collapse and limit the spread of water across plasterboard or insulation. Only do this if it’s clearly safe – if you’re unsure, it’s best to wait for a professional.

Make Temporary Repairs (If Safe)

If you can safely access your loft or a dry section of roof, some simple temporary measures may help prevent further water ingress:

• Apply roofing tape or sealant inside the loft to seal minor holes or membrane tears.

• Use a waterproof tarp to cover the affected area of the roof, only if the weather is dry and the wind is calm.

• Secure the tarp with battens or sandbags, avoiding nails or screws that might cause more damage.

Most importantly, never go onto a roof during rain, snow or high winds. If in doubt, stay inside and focus on limiting internal damage.

Document Any Damage

Before you begin clean-up, take clear, timestamped photos of all affected areas.

• Photograph the ceiling, walls and floors.

• Capture damaged furniture, electricals or fixtures.

• Include photos of any buckets, bulges or active drips to show the extent.

These are useful for insurance claims, future maintenance records or when seeking professional repair quotes. Although, note that most roof leaks will be classified as “wear and tear” by your insurer and are unlikely to be covered.

Call a Roofer or Leak Detection Specialist

Even if you’ve contained the leak, the underlying issue still needs to be resolved.

• Search for roofers using trusted platforms like Checkatrade, Rated People or TrustMark.

• Look for specialists who offer emergency callouts, temporary patching or professional leak tracing.

• Ask about non-invasive diagnostics, especially for flat roofs or properties with difficult access.

Prompt action from a qualified expert will ensure the leak is accurately diagnosed and fixed before more serious damage sets in.

If you’re managing a large or commercial property, or have more complex access requirements, our own roof repair service is the ideal solution. We creatively combine access methods to deliver durable roofing solutions that save you time and money.

Can You Repair a Roof Leak Yourself?

If you’re reasonably handy and confident with heights, the idea of fixing a roof leak yourself might seem like a good way to save money. But while some minor issues can be addressed with a DIY approach, roof repairs aren’t always as simple, or as safe, as they appear.

Here’s what you need to know before deciding whether to tackle the repair yourself or call in a professional.

When DIY Repairs Might Be Viable

There are a few scenarios where small, accessible repairs may be suitable for someone with the right tools and experience:

• Replacing a single broken tile or slate, especially on a low-level extension where safe access is possible

• Re-seating or re-cementing ridge tiles or hip tiles, if they’ve come loose and you have prior training in mortar work

• Refitting or sealing a small section of lead flashing, provided the area is easily reachable and you know how to avoid creating water traps

In these cases, if you have a sturdy ladder, appropriate PPE and confidence in your ability, it may be possible to carry out a basic patch. But even then, there are risks.

Risks of DIY Roof Repairs

While simple fixes might sound straightforward, there are several reasons to proceed with caution:

• Height and weather hazards: Roof work is inherently dangerous. Even a short fall from a ladder can result in serious injury, especially if working on sloped or wet surfaces.

• Misdiagnosing the problem: Water can travel far from the entry point. What looks like a broken tile might be masking a deeper issue in the underlay, flashing or even loft ventilation.

• Using the wrong materials: Not all roofing sealants, tapes or fixings are appropriate for every roof type. An incorrect patch could make things worse or void your roof or insurance warranty.

Unless you’re trained and confident working at height, the safest option is usually to call in a qualified contractor.

When to Call a Professional

Some issues are best left to experienced specialists, not only for safety reasons, but to ensure the repair is long-lasting and compliant with UK roofing standards.

You should always bring in a professional if:

• You suspect the leak is coming from a flat roof, as these require specific materials and application techniques.

• The flashing around a chimney or roof window is damaged, especially where leadwork is involved.

• You’ve tried a DIY repair before, but the leak has returned.

• Insulation, rafters or internal structures are damp or showing signs of rot.

• You’re unsure where the leak is actually coming from, or it’s not accessible from the ground or loft.

A professional roofer or leak detection specialist will be able to trace the root cause and carry out a safe, compliant repair, often without the need for costly scaffolding or intrusive access.

At Spectrum, we specialise in diagnosing complex roof leaks using advanced leak detection methods, especially at properties where traditional access is limited or previous contractors have failed to identify the source.

Step-By-Step: How to Repair a Roof Leak

While most roof repairs are best left to trained professionals, there are a few small-scale fixes that confident, safety-conscious property owners can attempt, particularly where the issue is clearly visible and easy to access.

This guide offers clear, practical steps to help you carry out minor repairs where appropriate and, more importantly, helps you understand when it’s time to step back and call in the experts.

Important: Never walk on a pitched roof and don’t attempt any repairs during bad weather. If the leak is extensive, difficult to access, or recurring, always seek professional help.

1. Start With a Visual Inspection

Begin by gathering as much information as possible. A visual inspection will help you confirm the likely source of the problem.

• Use binoculars from ground level to scan the roof for slipped tiles or slates, cracked flashing or sagging ridgelines.

• If safe to do so, inspect any lower-level roofs or extensions using a ladder, but never walk on the roof itself.

• Access the loft if possible and use a torch to spot damp insulation, mould patches or dripping water. Follow the moisture trail upslope if visible.

• Turn off the torch and look for any pinpricks of daylight.

• Look for signs of damage such as torn felt, exposed nails or daylight coming through timbers.

If the source of the leak is clearly visible and reachable, and you have the right tools and experience, you may be able to apply a temporary patch or carry out a basic repair.

2. Tackle Small Repairs (If Safe and Appropriate)

For accessible, isolated leaks, here are a few straightforward fixes you might consider:

• Seal exposed nail holes or gaps in the attic ceiling with roofing sealant.

• Replace a missing tile or slate, ensuring any nearby ones are secure and properly sealed.

• Refit or replace a small section of flashing if it’s clearly come loose or corroded.

• Replace or patch underlay (roofing felt or membrane) where it has torn, this may require lifting nearby tiles.

Be cautious: what looks like a quick fix may be masking deeper structural or moisture issues. Always inspect the surrounding area thoroughly, and don’t overextend your skill set.

3. Seal a Minor Flat Roof Leak

Flat roofs are particularly prone to damage, but if the problem is small and the roof is safe to access, temporary patching may be viable.

• Thoroughly clean the area around the leak to remove debris, dirt and moisture.

• Apply a suitable flat roof repair product, such as bitumen sealant or a rubber patch kit, over the affected area.

• For larger splits or tears, embed reinforcement mesh between two coats of the compound.

• Make sure the edges are sealed and feathered, and allow it to cure as per the manufacturer’s instructions.

For full guidance on materials, safety and when to escalate, see our complete guide to flat roof repairs.

4. Apply Temporary Waterproofing (If Bad Weather Is Imminent)

If a permanent repair isn’t possible right away, a temporary weatherproof barrier can help minimise internal damage until help arrives.

• Use a heavy-duty tarp to cover the affected section of the roof.

• Anchor it securely with battens, sandbags or rope, but avoid nailing into the roof, which can worsen the problem.

• Use waterproof tape or sealant inside the loft to patch minor felt tears or flashing gaps, if safe and accessible.

Monitor these temporary solutions closely – they’re not a substitute for proper repair.

5. Monitor and Recheck After Rain

Once repairs have been made or a tarp installed, keep a close eye on the affected area:

• Reinspect the loft and ceilings for any signs of continued dampness.

• Check insulation and timbers for new staining or moisture.

• Watch for water ingress during or after the next rainfall.

If the problem persists, becomes worse, or affects a larger area than expected, contact a roofing specialist for full assessment and repair.

DIY Roof Repairs: Weighing Up the Pros and Cons

Before deciding to carry out any repair yourself, it’s worth considering the benefits and the real risks of going it alone.

Potential advantages:

• Cost savings: If the repair is genuinely minor and you already have the tools and materials, DIY work can reduce labour costs.

• Flexible timing: You won’t need to wait for a contractor, which may help in a pinch, especially if you’re dealing with a light, active drip.

• Satisfaction and control: For those confident in their abilities, a quick fix may offer peace of mind and hands-on oversight.

Risks:

• Safety hazards: Working at height, especially on wet or slippery surfaces, carries serious risk. Without proper training and fall protection, even basic inspection work can be dangerous.

• Time-consuming: Without professional tools or a trained team, even simple jobs can take much longer than expected.

• Lack of proper equipment: Most DIYers don’t have access to industry-grade safety gear, ladders or specialist sealing products.

• Warranty issues: Many roofing products are only guaranteed when installed to specification by a professional, one misstep could void your cover.

• Inexperience under pressure: Roofing contractors handle these situations daily. A mistake in diagnosing or repairing the leak can lead to further water damage or the need for more expensive repairs later.

If there’s ever any doubt, whether about the cause, the condition or your own confidence, the safest and most effective option is to bring in a leak detection specialist and qualified roofer.

How Much Do Roof Repairs Cost in the UK?

Roof repair costs can vary significantly depending on the size of the problem, the type of roof and the level of access required. While some simple patch jobs may be relatively affordable, other issues, especially on flat or natural slate roofs, can quickly escalate in both complexity and cost.

Typical Repair Costs

Here’s a rough breakdown of the current price landscape for 2024-2025, based on the latest industry data and price guides:

• Small or moderate patch repair: £150-1,200

• Missing/damaged tile replacement: ~£200 for up to 5 tiles, assuming no scaffolding is required

• Roof leak repair (general): £100-2,500

• Roof valley repair: £75-600

• Flashing or leadwork repairs: ~£100 per metre

• Chimney stack repair: £200-400

• Gutter repair: £90-300

Cost Per Square Metre (For Larger Repairs or Replacements)

If the damage is widespread or requires full overlaying of sections, prices are typically calculated per square metre:

• Clay tile (pitched): £110-160/m²

• Concrete tile (pitched): £90-120/m²

• Natural slate: £150-220/m²

• Fibre cement tiles: £90-130/m²

• Felt roof: £100-140/m²

• EPDM (rubber) flat roof: £120-170/m²

• GRP (fibreglass) flat roof: £130-180/m²

These figures are indicative only and will vary widely by region, contractor and site-specific conditions.

Key Factors That Affect Roof Repair Costs

Several variables can influence what you’ll actually pay:

• Roof type and materials: Natural slate or GRP systems are more expensive than concrete tiles or felt.

• Size of the affected area: Larger leaks or widespread damage naturally cost more to fix.

• Access requirements: If your roof is particularly high, steep or obstructed, specialist access equipment may be needed.

• Weather and urgency: Emergency call-outs, especially during heavy rain, will carry a premium.

• Underlying damage: If water has soaked into insulation, timber or plasterboard, these will need to be repaired as well.

For reference, the average small-to-moderate roof repair in the UK currently costs around £550, but jobs can fall well above or below this depending on scope.

How to Prevent Future Roof Leaks

When it comes to roof leaks, prevention is almost always more cost-effective than cure. Most leaks can be prevented with proactive maintenance and regular inspections.

Whether you're managing a single residential building or a large commercial estate, a proactive approach can help avoid emergency repairs, structural damage, and disruption for tenants or residents.

Here’s how to reduce the risk of leaks developing in the first place:

Routine Maintenance

Proactive preventative maintenance is the best way to keep your property’s maintenance costs down. Staying on top of basic roof upkeep is the single most important step you can take.

• Inspect your roof twice a year. Make it a habit to visually inspect your roof in early spring and autumn, as well as after major storms. Look for missing tiles, cracked flashing or sagging gutters.

• Keep gutters and downpipes clear of leaves, moss and debris. Blockages can cause water to overflow into the roofline or penetrate under tiles.

• Check roofline components like fascias, soffits and verge trims. Damage here often indicates water problems further up the roof.

Regular visual checks and minor upkeep can significantly extend the life of your roof and catch issues before they escalate.

Proactive Upgrades

Some parts of a roof are designed to degrade over time, but that doesn’t mean you have to wait for them to fail.

• Replace ageing membranes or underlay before they become brittle or ineffective, especially on older pitched roofs.

• Re-bed and repoint ridge or hip tiles where mortar is cracked or missing.

• Seal or coat flat roof surfaces, where compatible, to improve waterproofing and UV resistance.

If the roof is nearing 15-20 years old or has had patch repairs in the past, it may be worth budgeting for these upgrades as part of your planned maintenance cycle.

Book a Leak Detection Survey

If you suspect water ingress but can’t identify a source, or if you manage large or difficult-to-access buildings, professional leak detection can be a game-changer.

• Early diagnosis helps prevent widespread damp, mould or insulation damage.

• Non-invasive tools such as tracer dyes, electronic sensors or thermal imaging avoid disruption or unnecessary access work.

• Ideal for flat roofs or hidden leaks, especially on commercial or multi-storey sites where water may travel laterally before appearing.

At Spectrum, we offer advanced leak tracing and reporting solutions tailored for complex buildings, helping you resolve issues before they cause major disruption.

Worried About a Leak? Let Us Help Before It Gets Worse

A roof leak can lead to soaked insulation, internal mould, electrical hazards and even structural decay. For landlords or building managers, it can also mean tenant complaints, compliance issues and costly downtime.

And the longer you wait, the worse it gets. Moisture can spread unseen through ceilings, rafters and wall cavities, turning a minor repair into a major rebuild.

At Spectrum, our leak detection and roof repair specialists use advanced, non-invasive techniques to locate and fix leaks quickly, often without the need for scaffolding, and with minimal disruption to occupants. From rope access inspections to precise leak tracing, we’re equipped to tackle even the most complex roofing challenges.

Don’t let a small issue become a big problem – get in touch today to book a roof inspection or leak detection survey and make your building watertight again.