A flat concrete roof is the most common source of seepage in Lahore homes. Heavy monsoon showers, ponding water, cracked screed and poorly sealed drains all let water into the slab, and it shows up as stains, peeling paint or drips on the ceiling below. Roof waterproofing puts a continuous barrier on top of the roof so water runs off to the drains instead of soaking in.
What's included
| Scope item | What it involves |
|---|---|
| Inspection and leak diagnosis | Checking slope, drains, cracks, parapet joints, pipe and tank penetrations, and the ceiling below |
| Surface preparation | Removing loose screed, old coatings or broken tiles; cleaning dust and moss |
| Crack and joint repair | Filling cracks, rounding the corner where roof meets parapet (a "fillet"), sealing around pipes |
| Slope correction (if needed) | Adding screed so water flows to drains rather than ponding |
| Waterproofing layer | Bitumen membrane, liquid-applied coating, cementitious slurry or another system, in the specified number of layers |
| Upturns and drains | Taking the layer up the parapet wall and properly into drain outlets |
| Protection / finish | A protective screed, tiles or a UV-resistant top coat over the membrane |
| Testing and handover | Water test where practical, written warranty, materials note |
When you need it
- Ceiling stains, drips or bubbling paint on the top floor after rain.
- Water ponding on the roof for hours after a shower.
- Visible cracks in the roof screed or around the water tank base.
- The roof has not been treated in many years, or a previous coating is peeling.
Step-by-step process
- Inspection. The contractor checks the roof and the room below, and identifies whether the leak is the roof, a pipe, a tank or a wall.
- Written proposal. System, layers, area, preparation, warranty and timeline in one document.
- Clear the roof. Move items, tanks on stands and solar frames as agreed.
- Prepare the surface. Remove loose material, repair cracks, and treat joints and drains.
- Correct the slope if needed. Let new screed cure as the contractor advises before coating.
- Apply primer and waterproofing. Follow the manufacturer's required drying time between coats.
- Detail the edges. Parapet upturns, drain outlets and pipe penetrations get extra layers or reinforcement.
- Protect it. Lay protective screed, tiles or a top coat so foot traffic and sun do not damage the membrane.
- Test. Where practical, block drains and pond water on the roof for a period, then check the ceiling below.
- Handover. Final payment, written warranty and a note of the products and layers used.
Approvals and documents
Waterproofing an existing roof is normally maintenance and does not need building approval. If the work includes building a new room, shed or structure on the roof, check with LDA, DHA or your society first. Keep your invoice and warranty in your property file; buyers often ask about roof treatment.
What affects the cost
Roof waterproofing is usually priced per square foot of roof. We do not quote rates; ask for written quotes. The price depends on:
- Roof area — larger areas usually cost less per square foot.
- System type — a single coating, a torch-applied membrane and a multi-layer system with protective tiles differ a lot.
- Removal of old layers — breaking old tiles or screed adds labour and debris disposal.
- Crack repair and slope correction — more preparation means a higher price.
- Number of drains, pipes and tanks on the roof — each penetration needs detailing.
- Access and height — carrying material up several floors adds cost.
- Warranty — a longer written warranty often costs more.
- Season — contractors are busiest just before and during the monsoon.
Questions to ask the contractor
- Where do you think the water is entering, and why?
- Which system will you use, how many layers, and what is the dry film thickness or membrane thickness?
- How will you treat the parapet joint, drains and pipes?
- Will you remove the old layer or apply over it? Why?
- Is a protective layer included, and what is it?
- Will you do a water test before final payment?
- What does the warranty cover, for how long, and what voids it?
- What happens if it rains mid-job?
Red flags
- A quote without a roof inspection.
- Coating over ponding areas without fixing the slope.
- No mention of drains, parapet upturns or pipes.
- Applying on a wet slab or just before forecast rain.
- A "lifetime guarantee" that is only verbal.
- Asking for the full amount before work starts.
FAQs
How long does roof waterproofing last? It depends on the system, the quality of preparation and whether the membrane is protected from sun and foot traffic. Ask each contractor what life they expect and what their written warranty covers.
Can I waterproof only the leaking part of the roof? Patch repairs can work for a single crack, but water often travels inside the slab, so a full-roof system is more reliable.
Do I need to remove old roof tiles? Not always. If tiles are sound and well bonded, some systems go over them. If they are loose or water is trapped beneath them, removal is usually better. Ask the contractor to explain their choice.
Can waterproofing and heatproofing be done together? Yes, and it is often sensible because both are laid on the same surface. Ask for a combined quote that shows each layer.
Will waterproofing fix cracks in the ceiling? It stops water entering through the roof. Structural cracks in the slab need an engineer's assessment first.
Sources
This page gives general practical guidance and does not quote rates or standards. Get written quotes after a site inspection.