31 August 2015
31 August 2015, Comments Comments Off on Double floor
Double floor

Single or… Double?

Over the years, the double floor has become a real must-have for high-end vehicles: any vehicle belonging to this small premium market segment is equipped with it. Here’s our analysis of the European market.

Words Michel Vuillermoz

In Europe the double floor is a must-have for top-of-the-range vehicles. The more luxury the motorhome, the more technologically advanced the double floor: with wood-free structures, replaced by polyurethane supporting panels, its heights can reach and even exceed 40 cm. Inside the double floor you can install tanks for clear and recovery water, water pump and pipes, loading and unloading valves, heating system radiators, on board equipments basic components, batteries, battery chargers, inverters, power stations, air conditioners. The best solution aimed at vehicles that feature the best technology available today. 

Within the 3.5 tons?
On larger vehicles, design is implemented without many compromises. However, what happens when you need to remain within the 3.5 tonnes? Starting from the assumption that the vast majority (75 %) of recreational vehicles produced today adopts, as base vehicle, the Fiat Ducato, the possible solutions are essentially two: either use the extraseries AL-KO AMC chassis, lowered and customized to best respond to the installers’ needs, or rely on the classic and functional Camping-Car Special Fiat chassis, in a 14 cm lowered version compared to the comparable high side-memebers equipped product of the Turinese factory, which not only is less efficient in terms of torsional rigidity but it is also less customizable than the special AL-KO AMC. Although they are two totally differently structures in relation to the design, torsional rigidity, suspensions and technical characteristics, they can be installed with a considerable height saving compared to the standard Fiat chassis: -22 cm for the AL-KO chassis, – 14 cm for the Fiat CCS. A veritable treasure to exploit for the double floor implementation, be it through type, i.e. designed in order to ensure free cross spaces aimed at storage and equipments housing, with an interspace over the entire surface of the vehicle, or technical, with an interspace sometimes located only in particular areas of the vehicle.

With 3.5 quintals, is double floor better?

On balance, then, for a medium size vehicle with an overall capacity lower than 3.5 tonnes, is it appropriate to adopt the double floor or not? From today’s marketed vehicles experience, we can draw some interesting conclusions. First and foremost, a vehicle equipped with double floor, regardless of the solution adopted (technical or through), is immediately perceived by the customers as more complete, more refined and more suitable for an all-weather use, including winter. The technical peculiarities developed by the different aforementioned manufacturers show that the adoption of the double bottom can be also consistent with the driving limits imposed by the standard driving license B, while at technical level, the placement of the most delicate components in special compartments not exposed to extreme temperatures (neither too hot nor too cold), dust, weathering or any debris, prolongs their life, under standard use conditions. The models featuring shallow water tanks placed at the center of the passenger compartment definitely show, especially in fully loaded conditions, a much higher road holding, with a low centre of gravity and a reduced tendency to roll when cornering. So, is all that glitters gold? Certainly not. A poorly designed double floor or, better, a double floor designed and built without taking into consideration its management and maintenance over the years along with the need for access to the standard maintenance operations, can prove to be a source of problems, whose solution sometimes is quite difficult. In fact, the vehicles in which it is possible to extract, in case of need, the tanks, or in which all the water system fittings are easily accessible in case of leaks are still few.


The most prestigious vehicles from Germany do not have internal floor hatches as they opt for the outer doors. On the new Flair vehicles, Niesmann+Bischoff has reduced internal hatches to one, i.e. the one accomodating the drinking water and gray water recovery tanks, which is located centrally in the cockpit. Morelo, a rapidly growing brand in the luxury vehicles industry, avoids any internal hatch to definitely solve the classic problem related to dust and/or debris transfer from the floor level to the double floor. Morelo, in particular, opted for a large number of external doors and chose a flat-surface lower floor, while not exploiting the chassis lateral spaces of the vehicle as it occurs with the new generation Flair instead. In both cases, the interspace features a remarkable height (42 cm in Morelo Palace, 34 cm in Niesmann+Bischoff Flair). Some manufacturers are characterized by a hi-tech walking surface. An example of this is the new generation Flair, featuring a 42 mm thick upper deck with double internal and external aluminum coating, synthetic reinforcements (Puranite) and closed cell foam-made internal insulation. Such a structure barely transfers the heat accumulated in the double floor to the cockpit, and it is therefore equipped with radiators included in the structure and connected to the Alde centralized heating system.

Frankia successfully designed a true double bottom in combination both with traditional Fiat Ducato AL-KO and the Mercedes-Benz Sprinter 500 Series with rear wheel drive on dual wheels. The Frankia double floor on Fiat AL-KO vehicle is a genuine through double floor: it contains the entire on board equipments – from the drinking water tanks to those containing the recovery water – houses the electrical system (batteries/chargers, distribution board), the heating system (not only pipes but also Truma Combi or Alde Compact thermal units), the loading/unloading and various equipments management valves and, of course, appropriate storage compartments accessible both from outside and smartly from the inside, with the chests lower deck hinged and book-folding to facilitate their handling. Conversely, the double-floor Frankia combined with the basic vehicle Sprinter 519 CDI essentially becomes a technical compartment, with a reduced centre height and large side lowerings. A structure therefore capable to combine with two extremely different basic vehicles, which in 2016 will be enriched with a new version, solely installed on Fiat AL-KO and designed to keep as much as possible the weight down. With the new Selection vehicles, in fact, the German company was able to combine its own through double floor design with weight limits by redesigning the interspace, whose opening changes from 34 to 25 cm, and by adopting a brand new alveolar floor, extremely lightweight while sufficiently rigid and strong at the same time.


Carthago has developed different solutions related to Fiat chassis with the extraseries AL-KO AMC chassis. The models included in C-Compactline and C-Tourer lines, in fact, are equipped with a double technical floor, featuring a 17 cm height, devoid of wooden structure (replaced by galvanized steel – made brackets), combined with a walking floor with multilayered phenolic double internal and external coating featuring extruded polystyrene insulation, primarily designed to house the heating system and water system pipes. A sort of heat-accumulating interspace, that was designed to transfer what was stored following the heating system use to the cell, but that, because of its reduced height, designed to reasonably restrict the total vehicle height, is forced to use a suitable insulated lowering in order to accommodate, the storage and recovery water tanks in the rear of the vehicle. On the contrary, for the Chic Online line, Carthago uses a through double floor on two levels, with 17 cm height in the front part of the living, lowered and coplanar compared to the driver’s cabin, and 30 cm in the rear part: a solution that if on the one hand requires the presence of a step in the centre of the passenger cabin, on the other hand has allowed the German company’s engineers to place all the on-board equipments inside the vehicle without lowering the tanks that, inter alia, have a higher capacity compared to the average. A further benefit from a solution of this kind regards, then, the rear bedroom accessibility, which, regardless of the solution adopted (transverse double bed /twin/central double bed) has a bed access threshold lower than the average while preserving a large garage (120 cm) below.

It resembles the design of the double technical heat accumulating floor created by Carthago and the double bottom used by Hymer for B-Klasse PremiumLine: the 12 cm high interspace hosts only the heating system and the water system pipes, while the tanks are housed in special insulated and heated polyurethane shells: a solution that has allowed the engineers to keep the total height lower than 290 cm, but that, on the other hand, has forced them to use the full living in line chest for the heating system thermal unit as well as the components of the electrical system housing, consequently depriving the crew of a conspicuous storage compartment.

Eura mobil
Among the strongest supporters of the double-floor we need to mention Eura Mobil: the German factory is in fact characterized by the generous volume of the subfloor interspace and has often turned this peculiarity into one of its strengths. All models produced, excluding the Profila One entry level, are in fact equipped with it, even though with substantial differences: the recent Integra Line motorhomes, as well as the semi-integrated vehicles with tilting Profila RS are equipped with a 11 cm high technical compartment essentially aimed at accompoating the water and electrical pipes as well as the heating systems items, while the drinking and recovery water tanks are housed in the the front living chests and in the underbody, respectively, enclosed in an insultaed and heated polyurethane shell. For these vehicles, the double floor supporting structure mainly consists of appropriate multi-layer items, while quite interesting is the case of Activa One top cabs, which have a 37 cm high through double floor as well as the merit of proposing this solution at a very competitive price. Installed on Fiat Ducato Camping-Car Special, although they cannot keep the total height lower than the standard three meters (313 cm, to be exact), they are a generous interpretation of the family vehicle designed for a four seasons use and marked by a storage capacity actually calibrated to this type of use, even with full crew on board.

In addition to the German manufacturers (first and foremost Buerstner and Dethleffs, which are strong double floor supporter for their high-end products), the double floor is becoming increasingly used even by Italian and French manufacturers: in Italy, in particular, Laika uses a true 20/30 cm high through double floor on Rexosline 9009, Kreos 7000 motorhomes and on the newest semi-integrated Kreos 5000 flagship models, all installed on Fiat AL-KO: the interspace runs along the whole surface of the vehicle, and it is accessible both from the outside through doors inserted at strips levels, and from the inside, through hatches equipped with automatic lighting and it houses the totality of the water system in a heated and protected environment: there are, of course, also ample storage compartments, especially in the area before the passenger compartment. The Tuscan brand has also developed, for the semi-integrated Kreos 3000/4000 and the Ecovip motorhomes, a different double floor design. Installed on Fiat Ducato CCS, these vehicles offer a double technical floor with two separate islands in the front and rear part of the passenger compartment, accessible only from the inside and designed to partially house the tanks for recovery water (front) and drinking water (rear) whose lower parts are included in special insulated and heated polyurethane shells. In order to keep the weight down, the Tuscant company’s engineers have used polycarbonate fiberglass sheets, combining them with the heating system special branches or convectors. The heights of the internal compartments depend on the different areas, 12 cm in the front part and 26 in the rear. Again the double technical floor, with 13 cm opening, equips the newest Mobilvetta K-Yacht Teknoline motorhomes.

In France, Pilote, Rapido and Fleurette are essentially the “double plancher” supporters. Pilote has made two different double floor versions, called DPS – Double Plancher Service, double service floor, with Ducato CCS, and DPR vehicles – Double Plancher Rangement, through double floor, with Fiat AL-KO vehicles. In particular, the DPR-identified vehicles feature 21 cm height in the front part and 33 cm in the rear. As to Pilote, it is interesting the possibility to order the fully-integrated vehicles complete with AL-KO chassis and double floor even with the most affordable Essentiel installation. This year also Rapido, along with the double-floor equipped luxury and consolidated fully integrated vehicles belonging to the 90DF, 10000 and Distinction series (whose double floor has been fully renewed and turned into a through one) offers this option also for the 80DF entry level, combined with AL-KO chassis as well.