A permanent, 5-year-warranted cure for leaking concealed box gutters at roof junctions, using liquid-applied and torch-on bituminous membranes. Specialist team with 15+ years of experience in Istanbul and Izmir.
Box gutter waterproofing is the renewal of the internal gutter (roof valley channel) that carries rainwater between two roof slopes to the drainage outlets, sealing it against leaks. The old membrane and debris are removed and the surface is prepared; a fully bonded liquid membrane or torch-on bituminous membrane is then installed to suit the gutter run and the direction of the falls. Junctions, outlets and chimney bases are reinforced with dedicated detailing. A drainage test is carried out and a 5-year written warranty is issued.
Box gutter waterproofing is the waterproofing treatment applied to the internal gutter (valley channel) where two or more roof slopes meet and where rainwater collects and is drained away. Because this channel sits beneath the roof covering and cannot be seen from outside, it is known as a "concealed box gutter". Rainwater from the roof surfaces collects in these channels and is directed to the gutters and downpipes; when the waterproofing fails, all of the collected water leaks straight into the building.
The box gutter is the most critical drainage point of the roof system. Carrying the greatest water load per square metre, it is also the roof element most exposed to thermal movement, UV radiation and mechanical wear. With the right material selection and professional application, box gutter leaks can be prevented permanently.
With more than 15 years of site experience and in-depth application expertise, İMG Yapı Yalıtım Mühendislik A.Ş. successfully applies both liquid membrane and torch-on bituminous membrane systems to box gutters. We determine the most suitable solution for the condition of your building and hand over the work with a 5-year written warranty.
The box gutter is the most critical drainage point of the roof. The falls of two or more roof surfaces meet in this channel, and rainwater collects here before being directed to the outlets. By its very nature, the box gutter is the part of the roof through which the most water passes per square metre. The constant flow of water wears and abrades the membrane far faster than on any other part of the roof. A membrane that might last 10-15 years on a normal roof surface can lose its function within 5-8 years in a box gutter.
Thermal movement is one of the primary causes of box gutter leaks. In daytime sun the roof surface temperature can climb to 70-80°C, then fall to 15-20°C at night. This daily swing of 50-60 degrees subjects the membrane to a continuous cycle of expansion and contraction. Over the years this cycle breaks down the material's molecular structure, robs it of its flexibility and creates micro-cracks. Separation occurs particularly at membrane laps and edge upstands. The narrow, enclosed geometry of the box gutter channel concentrates this thermal effect even further.
UV radiation and ozone gradually degrade the chemical structure of the membrane on the roof surface. The breaking of the polymer chains leads to hardening, cracking and, ultimately, water permeability. On top of this, leaves, twigs, dust and assorted debris block the gutter channel and prevent the water from draining properly. The ponding water forces its way through the membrane's weak points under pressure and reaches the roof structure. In winter, freezing water expands and mechanically tears the membrane.
The most insidious aspect of a box gutter leak is the distance between the point where the water enters and the point where it becomes visible. Water can travel metres through the roof structure and appear as a ceiling stain or a drip in a completely different location. This makes tracing the source of the leak difficult and demands a thorough inspection by a professional team. Superficial patch repairs mask the problem rather than solving it and can lead to greater damage. Thorough cleaning of the box gutter, removal of the old waterproofing and professional installation of the new membrane are the foundations of a permanent cure.
Staining, dripping and wet patches on the ceiling after rain. The leak rarely shows directly below the box gutter — it appears wherever the water has travelled.
Loss of flexibility, cracking and open laps in the membrane caused by UV, thermal cycling and water abrasion.
Leaves, twigs, dust and moss build up in the box gutter channel, preventing drainage and causing water to pond.
Prolonged leaking leads to rot in timber roof members, corrosion in metal components and loss of thermal insulation performance.
If you have noticed one or more of the signs below, your roof may have a box gutter waterproofing problem. Early intervention minimises structural damage and cost.
Brown or yellowish water stains on the ceiling after rain, wet areas and active drip points. If a stain keeps spreading, the leak is still active. There can be metres between the visible leak point and the box gutter itself.
Paint bubbling, plaster falling away and surface deformation on the ceiling or the upper part of walls. Moisture gets beneath the paint film and destroys its bond. Repainting does not solve the problem — the source must be cured.
Black or green mould patches along ceiling edges, at wall-to-ceiling junctions or in the loft. A serious health hazard — it can cause respiratory illness in particular.
Water leaking from the roof soaks the thermal insulation and destroys its performance. Heating costs in winter and cooling costs in summer rise noticeably. Once soaked, insulation never recovers its original performance even after drying out.
A mould and damp smell on the upper floors or in the loft is the herald of a chronic leak. Ventilation will not clear it — the source of the leak must be cured.
Water leaking through the ceiling can reach the electrical installation, creating a risk of short circuits, fire and danger to life. This sign calls for urgent professional attention.
Two core methods are used in box gutter waterproofing. The most suitable method for your building is determined by an on-site survey.
At İMG Yapı Yalıtım Mühendislik A.Ş.we apply both methods. During the on-site survey we determine the most suitable method for your roof's condition, the box gutter geometry, the climate and your budget — and deliver a solution backed by a 5-year warranty.
Our systematic, warranted application process, refined through more than 15 years of site experience.
Our specialist team goes up onto the roof and thoroughly inspects the box gutter channels, the junctions, the outlet connections and the condition of the existing membrane. The leak points are identified, and we establish which direction the water is coming from and where it is travelling. The general condition of the roof structure and the extent of damage to timber or metal members are assessed. The right diagnosis is the foundation of the right solution — with box gutter leaks, superficial repairs applied without tracing the source solve nothing.
If the existing membrane is cracked, has lost its bond or has blistered, it is carefully stripped out. Installing a new layer over old membrane leads to lap failures and renewed leaking in a short time. During the strip-out, the substrate beneath and the roof structure are examined; hidden damage comes to light at this stage. Where the existing membrane is still sound, a compatible overlay reinforcement is considered instead.
The box gutter channel and its surroundings are cleaned mechanically. Dust, debris, moss residues and loose particles are removed. Cracks, breaks and level differences in the surface are made good with repair mortar to create an even substrate. For the membrane to bond soundly, the surface must be clean, dry and even. A primer is applied to boost adhesion and ensure the new membrane stays bonded for the long term.
A liquid membrane or bituminous membrane is installed depending on the building's condition and the survey findings. Liquid membrane is applied by spray or roller to form a seamless, flexible waterproofing layer. Bituminous membrane is torch-welded into place to form a robust mechanical barrier. In both methods, special attention is paid to junctions, edge upstands and outlet connections. Polyester reinforcement tape and an extra coat are applied where required.
Once the membrane is installed, the box gutter channel is checked to confirm that water flows in the correct direction. The drainage falls are tested; we verify that water reaches the gutters and downpipes properly. Any inadequate falls are corrected. Gutter junctions and downpipe connections are checked for watertightness. Correct drainage performance directly determines the service life of the waterproofing.
A watertightness test is carried out; every junction, edge upstand and detail area is checked one by one. Additional work or reinforcement is applied where needed. Once the quality check is complete, the work area is cleaned and a 5-year written warranty certificate is handed over. Throughout the warranty period, any leak attributable to the application is remedied free of charge. Application photographs are archived and your project is kept on record.
For box gutter waterproofing to succeed and last, the following technical conditions must be met in full.
Real application stages from our box gutter waterproofing projects. Click a photograph to enlarge it.
In our box gutter waterproofing applications we use the liquid membrane, bituminous membrane and primer products of our own brand, Dryvatec. Because we manufacture and supply the materials ourselves, quality control stays with us from start to finish. No middleman margin — direct manufacturer assurance.
Dryvatec products are formulated to deliver high UV resistance, flexibility and mechanical durability on roof surfaces. They provide long-lasting performance in critical zones such as box gutters that are exposed to constant water flow and thermal movement. They are manufactured in accordance with TSE EN standards.
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The box gutter is the most critical drainage point of the roof. The wrong material or a faulty application can make the problem worse instead of solving it.
Every one of our box gutter waterproofing applications comes with a 5-year written warranty certificate. Any issue is resolved free of charge under warranty. Our application archives are kept on record.
We source the membrane and primer materials we use through our own manufacturing and supply network. No middleman margin — quality control is entirely in our hands. Direct manufacturer assurance.
Tracing the source is critical with box gutter leaks. Through a comprehensive roof inspection we find the true origin of the leak. We deliver a root-cause solution instead of a superficial patch.
Since 2009 we have waterproofed box gutters on every type of roof — concrete flat roofs, under-tile roofs, sandwich panel and timber roofs alike.
Rapid response to every district from our Maltepe (Istanbul) and Konak (Izmir) offices. On-the-ground teams and material depots in both major cities.
If box gutter waterproofing alone is sufficient, we will not recommend renewing the whole roof. We define the scope according to the real need and never generate unnecessary cost.
From our two offices we provide box gutter waterproofing services across every district of Istanbul and Izmir.
From our Maltepe office we provide box gutter waterproofing across every district of Istanbul. On-site surveys and application on both the European and Asian sides.
From our Konak office we provide box gutter waterproofing across every district of Izmir. A wide service network across the Aegean region.
We have compiled the questions our customers ask most often, together with the technical answers.
A permanent cure for leaks and damp on flat roofs and terraces using membrane and liquid-applied waterproofing. 5-year warranty.
DetailsA permanent cure for leaks at expansion and movement joints using flexible membrane and sealant applications.
DetailsProfessional waterproofing solutions for damp and moisture problems throughout the building. Source diagnosis and permanent treatment.
DetailsFill in the survey request form or call us about the leak in your box gutter. Our technical team will get back to you promptly to arrange an on-site assessment and survey.
