Ballasted roofs: why gravel, and how to protect their waterproofing
Something of an innovation in the Italian building scene, while also being a useful device for protecting the roof, the ballasted flat roof is a solution that can become a distinctive feature of either a residential or commercial building.
Unlike the traditional system involving the use of concrete, using gravel is an option that brings a number of attractive advantages:
- it protects the roof against wind and UV rays
- it protects the roof against mechanical damage
- it is low maintenance
- it provides thermal comfort in summer as it shades the roof
- it makes the whole roof system practically fireproof
- it is long lasting.
In building, the choice of a ballasted roof is often prompted by aesthetic reasons for a holiday home or a hotel by the sea, or in an area with high sunshine hours… while it also caters to the need for optimal insulation and low maintenance.
The TeMa Building Solutions answer for protecting ballasted roofs
When gravel is laid, the load can tear the waterproofing layer on the roof underneath, and this comes with the risk of leaks, with all the ensuing stain, mould and structural damage issues.
So it is important to address the need for rainwater drainage and mechanical protection of the waterproofing.
TeMa Building Solutions has come up with a product that serves multiple functions: the product in question is T-Kone G Drain, the studded membrane (which serves to protect the waterproofing) featuring a geotextile (addressing the need for filtration and separation).
Placed between the gravel layer and waterproofing, T-Kone G-Drain is thin, strong and ideal for an effective build-up without the bulk.
- Published in Ballasted roofs, BUILDING, Studded membranes and accessories
Green surfaces and green roofs: benefits and technical ins and outs
In recent years, “green” has become more and more of a buzzword, encompassing simple and cost-effective solutions that can be adopted by anyone with a roof. We’re talking green roofs, which, in addition to bringing undeniable environmental benefits, are the perfect place for relaxing with the family or enjoying summer drinks with friends. The origins of roof gardens date back to ancient times — think Hanging Gardens of Babylon — and, today, are built for extreme reliability, including long service life, with excellent products producing even more advantages.
Let’s take a look at the full picture in detail.
The advantages of green areas
For the environment
Plants and grass are natural carbon sinks, absorbing CO2 and releasing oxygen, in addition to filtering particulate matter. In addition, they lessen the urban microclimate effect by lowering temperatures by several degrees centigrade, and reduce electrosmog caused by any electronic device.
They muffle noise and, if designed well, absorb and retain the early sudden downpours associated with significant rain events.
A series of sustainable improvements for urban wellbeing, improving air quality with less smog and particulate matter.
For occupant comfort
Vegetation also acts as natural thermal insulation — which is no small advantage given the energy crises of recent months — and soundproofing in loft bedrooms. Furthermore, it provides the roof with effective protection against UV rays, mechanical stress and daily variations in temperature, thus increasing the average service life of waterproofing.
Lastly, creating a garden on a roof increases the value of the property.
From a technical point of view
A green roof build-up comprises a number of layers, including geosynthetics offering better performance than traditional systems in terms of drainage, mechanical protection of waterproofing, and filtration. The products used are lighter and non-bulky, easy to transport and quick to install.
Functions required of the roof
There are 4 main functions involved:
- Reservoir (to hold rainwater for irrigation purposes until it is needed) and drainage (to remove excess water). This combined function is addressed with 20mm HDPE studded membranes T-Kone H XL and T-Kone H XL S.
- Control of surface erosion caused by atmospheric agents. This function is addressed with natural fibre matting T-Juta 500 and the synthetic geomat T-Mat.
- Drainage. This is where T-Mix Drain 20 SS comes in, the cuspated-fibre geomat sandwiched between 2 geotextiles.
- Mechanical protection of waterproofing. The geotextiles from the Tematex NW PET range, in white and black, fit the bill.
- Published in BUILDING, Flat green roofs
Tips for the correct laying of TMD 1011
For vertical applications, such as foundation walls, and for horizontal applications, such as flat roofs, mechanical protection of waterproofing is required and, often, also drainage: TMD 1011 is a studded membrane, produced by TeMa Building Solutions, that performs both functions: drainage for vertical applications and waterproofing protection for horizontal applications.
A few tips for laying TMD 1011 on horizontal surfaces
Flat roof with gravel finish (weighted)
1 Gravel finish
2 TMD 1011 membrane serving as a drainage layer and for waterproofing protection
3 Waterproofing membrane
4 Thermal and acoustic insulation
5 Vapour barrier
6 Sloping underlayment
7 Load-bearing structure
Walkways and green areas
1 Interlocking block paving
2a Crushed stone bedding course
2b Growing medium
3 TMD 1011 membrane serving as a drainage layer and for waterproofing protection
4 Waterproofing membrane
5 Vapour barrier
6 Sloping underlayment
7 Load-bearing structure
Surfaces suitable for vehicle traffic A
1 Paving designed to take vehicle loads
2 Sand bedding layer
3 TMD 1011 membrane serving as a:
– drainage layer
– substrate in place of traditional concrete levelling compounds
– separating and leachate containment layer (oils or hydrocarbons)
4 Substructure / ground
Surfaces suitable for vehicle traffic B
1 Paving designed to take vehicle loads
2 Sand bedding layer
3 TMD 1011 membrane serving as a drainage layer and for waterproofing protection
4 Waterproofing membrane
5 Sloping underlayment
6 Load-bearing structure
A few tips for laying TMD 1011 on vertical surfaces
Unroll the membrane and install it vertically or horizontally: in the latter case, the width of the roll corresponds to the height of the wall to be protected. Two consecutive membranes should overlap by about 20 cm, and the studs should interlock.
For horizontal joints, if the TMD 1011 membrane is not wide enough to completely cover the height of the installation, the first layer should be installed from the base upwards and then, keeping an overlap of at least 15 cm, the second layer should be installed by overlapping the first layer outwards (i.e. towards the side away from the wall). Install washers every 20 cm in the overlapping area.
Inlets for utility connections, such as water, gas, sewers or similar pipelines
- Place mastic sealant around the pipeline or inlet.
- Cut the TMD 1011 membrane vertically so that it extends 15 cm beyond the pipeline or inlet, trimming the membrane so that it adheres as tightly as possible.
- Put mastic sealant on the membrane so that there is a layer of mastic both above and below the membrane around the pipeline or inlet.
- Start the next installation of the membrane 15 cm before the pipeline or inlet so that the overlap around the pipeline or inlet is 30 cm. Trim again around the pipeline or inlet for watertightness.
- Install fasteners every 20 cm along the edge of the overlapping membrane.
Change of level or areas where the smooth part has been trimmed
Use T-Profile + T-Nails to seal the edge, using a sealant for the area to ensure that the edge is properly sealed.
TMD 1011 should also be protected with T-Profile to prevent soil from penetrating into the gap between the wall and membrane. Then, fasten it using washers and nails with T-Nails spaced at intervals of 20-30 cm, either along the upper edge of the studded membrane or along the profile.
Drainage for diaphragms and berlin walls: a practical and safe solution
Some of the most widely used works in the civil engineering field are diaphragms and berlin walls, which counteract strong thrusts of the soil and prevent landslides and structural subsidence.
Diaphragms are supporting walls consisting of pointed vertical elements (piles) or continuous elements (walls) made of steel or reinforced concrete. They are driven into the ground to a considerable depth, whereas Berlin walls are flexible retaining structures constructed with vertical micro-piles.
Both solutions are used where it’s impossible to construct excavation walls of an adequate gradient due to the presence of other nearby structures and to the morphology of the area , which imposes limited work spaces (that would make manoeuvring large machinery impossible).
Berlin walls made of micro-piles are one of the most popular applications on construction sites for implementing waterproof retaining works. The technique allows work to be carried out on almost all types of terrain, especially when it’s necessary to use on-site systems that are smaller than in the past.
Since works are in contact with the ground, the drainage aspect should not be underestimated. If rainwater and groundwater exert pressure on the vertical wall, they may damage the waterproofing. TeMa Building Solutions therefore has the right product for this application: T-Mix Drain WP, the geocomposite that not only drains but also provides the functions of filtration, separation and stay-in-place formwork.
TeMa has acquired considerable experience with geocomposites. For many years, the company has been providing this system to replace the conventional gravel drainage system. The results are long-lasting and it’s the ideal solution: compared to conventional gravel, it’s less bulky, easily transported and quick to install. This reduces the costs of transport and implementation and on-site construction time while, last but not least, resulting in considerable savings in terms of CO2.
Fields of application
As mentioned above, diaphragms and berlin walls are widely used where space is limited. More specifically, they can be used in the construction industry, for example for underground garages in homes or commercial premises, for basements. They can also be used in river works, such as quays and piers for boats, or in earth dams and wells.
Having the experience of TeMa technicians and tested effective products such as T-Mix Drain WP at your disposal is therefore a guarantee for your construction site.
Waterproofing when concrete casting
Concrete casting involves creating a new concrete element as a continuation of an already existing one. Most often it’s impossible to create a monolithic block with a single casting: consider, for example, very large structures or the connection between vertical and horizontal walls. With concrete casting you can obtain monolithic structures with their own characteristics, built in stages at subsequent times. So, you proceed with small blocks and join each casting to the previous one, creating a monolith piece by piece.
Structural connection is achieved by using reinforcing irons, taking special care with drilling the existing block and the length of anchorage. While ensuring attachment to the sequence of blocks, reinforcing irons are potential lines for water seepage. We well know that accumulation of moisture in walls may have very severe consequences: structural fragility and very unhealthy stains and moulds.
An effective solution is to insert bentonite kerbs which waterproof any voids that may have formed at the base of walls or in contact with reinforcing irons. The intrinsic property of sodium bentonite is exploited, which is the ability to swell on contact with water, filling the available space and forming an impermeable compound.
Furthermore, this material provides high resistance to hydraulic load, is easily applied and adheres perfectly to the support.
The range of building products from TeMa Building Solutions also includes T-Bentostop, the waterstop made of hydro-expanding bentonite for waterproofing and sealing concrete casting.
Concrete industrial paving: How to ensure versatility and durability
A factory layout determines the physical positioning of machines, workstations that develop individual processes and service departments in order to make the work of people, machines and materials more efficient.
Paving is subjected to continuous stress and have to withstand considerable loads. Concrete has its own characteristics to meet these needs and is also very aesthetically versatile, which means that it’s often used by designers in domestic and commercial contexts, both indoors and outdoors. Moreover, it can be quickly customised with textures or other types of printing.
What functions are important in industrial contexts?
Industrial paving inevitably suffers wear and tear from prolonged and intensive use.
It is therefore necessary to guarantee high compressive strength. This is because the surfaces of environments such as warehouses and industrial facilities are constantly subject to heavy loads: storage shelving systems, machinery and moving vehicles such as pallet stackers and forklift trucks. In many cases, weights are concentrated more in some places than in others (e.g. the areas where pallet stackers move or the quintals of goods in the warehouse that weigh down on the same spot for a long time).
This can also cause fissures and cracks on the surface that would hinder access and make it difficult to carry out normal work activities.
Lastly, as already mentioned, concrete is a very versatile material that can be laid over other types of substrate and also customised as required.
How to achieve an optimum and long-lasting result?
Thorough planning from the outset and the choice of suitable materials is the first step to a successful result, but painstaking attention during laying is also important.
The product range from TeMa Building Solutions includes specific products for the reinforcement of this type of paving. T-Fiberglas CLS mesh, made of fiberglass and coated with a special alkaline dressing, is designed to reinforce horizontal concrete applications, whereas T-Zink Net is the anti-cracking mesh made of galvanised steel.
- Published in BUILDING, Concrete paving
Rooftop car park: next-level solution for making the most of underused space.
City centres are overcrowded with vehicles and restricted areas, car parks are “stressed” and there are never enough spaces to go round. Alongside the more “standard” trafficable ceiling slab solutions — such as in the case of underground garages — it’s not too much of a stretch, where structurally feasible, to think about designing or making better use of spaces on elevated levels.
Over the holidays, car parks on the roofs of public buildings or buildings for use by the public could also provide refuge for the cars of passers-through. During the offices’ closing time, for example, these parking spaces can become a real asset, an ideal solution for making use of otherwise unused space and increasing the number of car parks for people travelling to tourist hot spots
Continual vehicular traffic and exposure to the elements — from freezing temperatures to sweltering heat — mean the construction materials used must be fit for purpose. Intensive use means it’s imperative all the proper layers are in place (build-up design) to serve the different specific functions. Let’s see what these layers are.
What do we need to be careful about when designing a rooftop car park?
This kind of roof is subjected to high loads, both static and dynamic, from vehicles of all kinds. This makes the mechanical protection of the waterproofing layer and the need for high compressive strength two key focus areas.
Drainage is another aspect to be factored into the design. Rainwater can seep into the underlying layers and damage them, so we need to ensure that water is drained off the roof properly.
We recommend applying studded membranes laminated with nonwovens or drainage geocomposites made from monofilaments or geonets.
Our drainage geocomposite T-Mix Drain Plus is a good candidate for the drainage layer. Alternatively, you can opt for the T-Net Drain 5 and T-Net Drain 7 geonets, which are sandwiched between nonwovens.
The job of mechanical protection, together with drainage, can instead be handled by the drainage geocomposite TMD 1011. The product consists of a filter geotextile laminated to a studded membrane, whose conformation delivers effective drainage even under the strain of high loads (up to 400 kPa).
- Published in BUILDING, Drainage geocomposites
Vapour diffusion, retarder and barrier: how do they differ?
On flat or sloping roofs, water and moisture arrive from outside with atmospheric precipitation. However, water seepage is just as hazardous and is created inside with vapour that may accumulate as a result of temperature changes between outdoor and indoor environments.
In building elements, the persistence of moisture and condensation can cause a structure to deteriorate. This is evident in the appearance of efflorescence (those white spots that appear as a result of the solidification of salts contained in water) and, subsequently, mould.
Multilayer vapour membranes are excellent for protecting buildings against water seepage. They can be divided into vapour diffusion, barrier and retarder.
Although often confused and considered interchangeable, they actually perform quite separate functions.Let’s take a look at them in detail.
What makes them differ?
What makes these products differ is mainly the degree of vapour breathability, its resistance capacity, measured with an Sd indicator. The lower the Sd value, the more breathable the material. The UNI 11470:2015 standard sets out application methods for breathable screens and membranes and their use on pitched roofs, on continuous or discontinuous supports or in direct contact with thermal insulation.
With Sd ≤0.1 m, diffusion membranes are impermeable to water but highly permeable to vapour that is created in a room and can escape.
On roofing, a breathable diffusion membrane is applied to the outside of a building over insulation, as it facilitates the evaporation of moisture, even residual moisture, whereas on the inside – below the insulation – a retarder or barrier should be chosen.
TeMa Building Solutions suggests T-VAPO FAST 150, T-VAPO FAST 180 andT-VAPO FAST 210.
These membranes (2 m < Sd ≤ 20 m) completely block the passage of water but only partially block vapour, thereby controlling the passage of moisture and preventing the formation of interstitial condensation.
They are generally placed inside a structure because it slows down the passage of vapour that is conveyed, in winter, by warm air to the outside and which might deteriorate materials.
TeMa Building Solutions suggests T-VAPO SLOW NET.
N.B. The watertightness of breathable membranes and vapour retarders refers to their ability to withstand rainwater if a roof covering is damaged or breaks: it should not be considered in relation to pressurised water.
Lastly, a vapour barrier is a material that is completely impermeable to both water and vapour (Sd ≥ 100 m). It is mainly, but not exclusively, used in humid environments such as swimming pools.
The position of a vapour barrier depends on the heat flow: it should be placed against insulation on the warm side.
TeMa Building Solutions suggests T-VAPO STOP and T-VAPO STOP ALU.
Which one should you choose?
There is no single answer. A technician will recommend the right product after a passive thermographic analysis and precise thermal engineering design. In principle, the most important factor is to block vapour where it forms while allowing any residue to pass through so that the waterproof layer remains intact.
As mentioned above, choosing which membrane to use requires an evaluation of various aspects, including climatic conditions, the type of insulation, structural components and a technical assessment based on thermo-hygrometric measurements.
Discover the full range offered by TeMa Building Solutions here.
- Published in BUILDING, Vapour barrier, Vapour diffusion, Vapour retarder
“A wet February, a good year”, as the saying goes. But not for walls!
Many factors can influence the presence of damp stains on the walls of your home. It isn’t pleasant to find that your walls are damaged low down and you need to do something about it. However, there are ways to prevent the problem directly.
Let’s take a closer look at the causes of damp walls and the best way to deal with it.
What causes damp in interior walls?
The main causes are:
- A burst pipe: as damaging as it is unpredictable, it leads to water leakage that very quickly makes the consequences apparent.
- The absence of waterproofing: walls in contact with the ground are exposed to rising damp from the ground. During the construction stage, it’s therefore necessary to waterproof the building, giving special attention to ground floors and basements, especially in the case of country cottages and villas.
- Damage to the waterproofing layer: as previously mentioned, it’s good to waterproof, but it’s also necessary to apply a protective layer that can withstand heavy loads and hydrostatic thrust from the ground. Only then will the waterproofing last intact.
- Inadequate ventilation of rooms: air saturated with moisture creates no less damage than the factors described above. If a wall is cold and the interior of a room is warm, water vapour turns to condensation. It is therefore advisable to provide adequate ventilation of rooms.
What are the consequences?
First of all, there is efflorescence, i.e. the solidification of salts in water, which appears as white spots. This is followed by swelling and flaking of the plaster.
Lastly, mould stains may appear.
This affects the aesthetic appeal of rooms, but even more so their liveability: unhealthy and potentially harmful mould and damp can cause much damage to human health if not quickly removed.
What NOT to do?
Unfortunately, mould and damp appear and we can try to contain (cover) the damage.
It’s a good idea to consult a specialist to find out the extent of the problem and possibly find a tailor-made solution.
But it’s certainly not a solution to try and cover up the damage, like sweeping the dust under the carpet: the problem remains. What’s more, there’s the risk of it recurring and getting worse because insulating paints and tiles prevent it from drying out.
How to prevent it: recommendations from TeMa Building Solutions
Prevention is always the best approach in this case: by providing appropriate waterproofing, drainage solutions and mechanical protection of the waterproofing from the outset, you can avoid the costs and difficulties that would arise once the damage has been done.
TeMa Building Solutions therefore recommends itsT-Kone Plaster studded membrane and its accessories.
The studs create an air gap of 8 mm that ensures constant air circulation and, thanks to the profile at the base, eliminates excess moisture. It needs to be applied with the nails provided after cleaning and levelling the surface, thereby providing perfect adhesion for plaster.
Go to the specific page to learn more.
- Published in BUILDING, Thermal insulation and ventilation systems