Insulation & Lining

Converting a Citroen Relay (Ducato or Boxer) into a Motorhome – Insulation and Lining

Introduction – Citroen Relay self build motorhome.

In this section, Insulation and Lining I share my experiences on completing what I found to be the most time consuming part of the build. 

The first stage in my project was to fully clean and strip out all existing lining and the steel bulk head.  This would give me the all important blank canvas.  As with any secondhand vehicle, the van needed a deep clean. Indeed, this was especially important as the van had been used by an engineering company and was very oily. 

My father, Paul is always keen to help on projects and his efforts assisting me cleaning the van were much appreciated! Between us, we used a range of products including white spirit, de-greaser and upholstery cleaner. However, the main requirement was sheer hard work. By the end of a very long weekend, I was left with a blank canvas and nice smelling upholstery.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: oily floor looking forwards

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: oily floor side view.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Removing ply floor rear

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: oily floor removed

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: cleaning cab Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Cleaned cab

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: cleaned rear

Stage 1 – Citroen Relay self build motorhome: Fitting cab carpet.

Finally, the unpleasant but necessary task of cleaning the van was complete! The next stage was to begin the installation of the floor.  As part of the cleaning process, it was necessary to remove both front seats. This was the ideal opportunity to fit the carpet in the cab.  The carpet itself was second hand but in excellent condition and had been given to me by an aunt who had recently refurbished her house. My carpet was a maroon coloured dense pile with hessian back. The colour and inherent strength would be more than adequate for the purpose. To ensure that the carpet would not move whilst driving or walking over it, I ensured that the fixings used to hold the plastic trim in place passed through the carpet.  I also used the off-cuts to line the three shelves above the glove-box and am very happy with the results.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: cab carpet fitting start

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: cab carpet fitting

Stage 2 – Citroen Relay self build motorhome: Rear flooring.

Once the cab was reassembled, I turned my attention to constructing the floor in the camper section.  My design included installing the lightweight interior from a caravan.  These units rely on a solid floor for their strength.  I therefore took the decision to use 12mm ply which whilst heavier than 9mm ply, would give me a solid base to work from. 

Support Framework.

First, I set about installing 26mm thick battens across the floor at regular intervals. This would allow for a layer of 25mm insulation board between them. Since the 8×4 sheets of ply were to lay across the van, I ensured that there were battens at 1220mm and 2440mm centres from the front. To avoid squeaks, I took care to cut each batten around 3mm short. This would ensure that they would not rub against each other.  In addition I bedded each batten in silicone to isolate them from the floor.  Each batten was screwed through the floor with stainless steel screws, again sealed with silicone sealant.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Floor battons front

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Isolating floor battens

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: placing floor batten

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Floor battens completed

Insulation Board

After the battens were installed, I filled any remaining holes (from where the original van’s floor had been fixed) using silicone sealant. I then set about installing the insulation board. Here I chose to use 25mm closed cell insulation board. Mine was branded as Xtratherm, Celotex, but there are many different suppliers.

I used 2 ½  4×8 sheets at a cost of £23 each. My rationale behind using such board was its impervious to water and could be easily cut using an old carving knife.  Again, each piece of insulation board was installed on a bed of silicone sealant. I included a 10mm gap around each side to fill with foam.  I have since found that this extra step has been worthwhile as there are no squeaks from the floor at all.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: fixing insulation

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: insulating floor completed

Expanding Foam.

 Once the insulation board was installed, the next stage was to seal around the edges with expanding foam.  I was however concerned that the foam would expand below the board.  In order to reduce this risk, I decided to temporarily fix battens across each board.  These battens would hold the insulation in place until the foam had finished expanding – It worked…

I tried a number of different foams and found that Screwfix’s cheapest ‘no-nonsense expanding foam’ was excellent and highly recommended.  The foam is a messy product and wearing gloves is a must. It is very important to wear a mask (I am not in these photos but did from immediately after the photo was taken) as it is poisonous.  I allowed 24 hours for this to set before removing the supporting battens and trimming the excess foam.  An old 9” carving knife was great for this task!   It is important to note that I kept all of the excess foam as I intended to use this later.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Flooring expanding foam

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Flooring expanding foam continued

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Flooring expanding foam completed

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Flooring expanding foam cut back

Ply Boarding

Now I had a fully insulated floor, it was time to install the 12mm ply boards. I knew that I would want to fix things to the floor at a later date and so I took a series of photographs with a tape measure laying across the floor to show where each batten was located.  The ply boards were simply marked out and cut using a panel saw and fixed in place with 8x 1 ¼ “ screws at 150mm centres. Unfortunately my memory card became corrupted and the photographs cutting the ply have been lost.  I checked each screw was tight and then sealed around the wheel arches using more silicone sealant before sweeping the floor and declaring the floor finished!

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Floor batten locating rear

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Floor batten locating front

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply floor rear

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply floor completed offside

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply floor comleted nearside

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply floor completed rear

Stage 3 – Citroen Relay self build motorhome: Lining the walls.

Foil backed bubble wrap.

Now I had a strong floor, the next stage was to insulate and board the side walls of the van.  My research had shown me that a common problem with motor homes converted from panel vans is rusting side panels and sills caused by condensation.  To overcome this, and to add an extra level of insulation, I decided to install a layer of foil backed bubble wrap to the interior walls.  Each 10m long 500mm wide roll cost £12 at Wickes.  I found that spray contact adhesive from Screwfix at £2.50 per can worked a treat. To cut I simply used kitchen scissors.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Insulating walls with foil bubblewrap

The bubble wrap made a noticeable difference to noise levels as well as warmth and so, in my opinion is definitely worth doing. 

Insulation board.

Once I completed the bubble wrap, I cut more insulation board and stuck this to the bubble wrap using more of the spray contact adhesive.  I let the adhesive dry for a few hours before using the spray foam to seal all of the gaps.  I also used the excess dried foam from the floor to pack out the box sections to reduce the number of cans required to complete the job.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Insulation board side

Timber framework.

Once a single layer of insulation board had been installed over the bubble wrap my next job was to install the timber frame to the steel work in order to support the ply lining.  This was a slow process as I wanted the sides to be as near vertical as possible to ensure that the caravan interior would fit correctly.  Each piece of pine had to be shaped, however I would later appreciate the efforts at this time, it also involved cutting some of the insulation board and foam installed in the previous stage, indeed in retrospect if I were to repeat this project, I would install the framework before installing the insulation.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Installing wooden framework front

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Installing wooden framework rear

More insulation board and foil backed bubble wrap!

Once the timber frame had been installed, I added extra layers of insulation board again using the spray contact adhesive.  This aspect of the project was somewhat time consuming as I had to reduce the thickness of the final layer of insulation board to ensure that its surface was around 3mm below that of the pine frame to allow for a second layer of foil bubble wrap over the top.  The second foil layer was intended to act as a vapour barrier between the ply and the timber frame, to ensure this was as impervious as possible, each joint was sealed with foil tape.  The flush finish of the insulation also ensured that should any adhesive fail, the loose insulation would not move and squeak.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Sealing insulation offside

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Sealing insulation nearside

Ply lining.

The timber framing and insulation took far longer than I had hoped, however I feel that it was worth the pain as I remain confident that the structure will last well into the future,  Once the lower panels were complete I began shaping the 9mm ply to be installed over the top.  I began by rough cutting the panels to enable me to move them within the van, I then offered them up in position and marked the corners directly onto the board.  In order to ensure that the van was as wide as possible, I cut a horizontal channel using a plunge saw and chisel around the strengthening box section as shown below.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply lining shaping

Stock sizes of ply, i.e. 8×4 sheets were smaller in size than the original vans boarding and so I found it necessary have a vertical join on each panel. The lap joint can also be seen in the above photo where I have glued and screwed an off-cut in position. I had to cut back the insulation locally to enable this to fit and again ensured that the wall was sealed with more foil tape!  Finally the panel was screwed into place using 8×1 ¼ screws.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply lining offside

Stage 4 – Citroen Relay self build motorhome: Lining the roof.

Once all of the lower walls were lined, I moved onto lining the roof.  This was similar to the process of lining the side walls, however the construction of a wooden frame was unnecessary as there were enough structural members to give a satisfactory fixing for the boards. 

Insulation board and foil backed bubble wrap.

Once again, I lined the steel panels with foil backed bubble wrap before sticking the insulation board in place using spray contact adhesive.  It was important that the insulation was the same thickness as the reinforcement members to prevent it rattling above the ceiling as a result of the contact adhesive failing due to potentially high temperatures on the roof.   In order to achieve this, I packed out areas with further bubble wrap and strips of insulation board before using foil backed adhesive tape to seal all joints and damaged areas of the insulation board.  

Ply lining.

The final stage was to cut the 9mm ply to size and screw up as before.  To make this a little easier, I used ‘Acro props’ to hold it in place until all screws were fitted.  The following photos show the insulating and lining of the roof.

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Insulating roof side door

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Insulating roof complete

Citroen Relay, Fiat Ducato, Peugeot Boxer Self Build Motorhome: Ply lining roof

For further information on my Motorhome conversion, please click here!

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