Pool with jacuzzi building at Spa Villa Agata in Croatia

Pool jacuzzi construction at Spa Villa Agata in Croatia

Pool jacuzzi building process as part of Spa facilities at Villa Agata in Croatia displayed in an image gallery.


This Pool jacuzzi building project was specifically designed to be attuned and integrated into ambiance and feel of existing outdoor sauna. With an intention of creating a wellness type surrounding, pool with jacuzzi is positioned in the middle of courtyard between sauna and lounge area.


Process of Villa Agata pool building started with excavation of a hole shaped in a way that can accommodate 20-30 cm thick concrete walls. Planned design of completely circular features along with curved stairs and edges will definitely add some extra effort but, when you’re building by yourself, there is no one to complain about it :)..
DIY pool will also be of two different levels of depth, 1.5 meters on deep part and 0.6 meter at the shallow part, along with an elevated 1 meter deep jacuzzi with a concrete seating. These are depts at the final stage of pool with final layer already finished and measured from water top level. Jacuzzi will be connected to the main pool by a waterfall made by a tongue shaped spillway on top. What needs to be done next is establishing final borders of the pool by using planks, and marking those planks to level the top of the pool.


First major issue while digging appears to be the very thick, almost rocky clay soil starting at about 1 meter depth below what on top is soft grass lawn. Alltogether we have to get to the depth of the pool plus 20 to 25 cm of concrete plus about 10 cm for the drainage pipe. It would not be a problem for a mini excavator, but excavator here would have a problem accessing the spot because of walls all around the courtyard. Because of not that huge volume of this pool (about 20 cubic meters), and because it is partially above ground, I decided to take that shovel and not have to visit a gym for quite some time. Also, the soil excavated would come great to finally level that slopy part of lawn behind the house. This way, there will not be any piles of soil making it harder to move around later, but it will be taken right away to it’s new place. Drainage pipe will be laid on the bottom of the shell of the pool and covered with gravel in a way that gravel covers the pipe in full. Pipe exits the pool bottom into the canal in a way that it always inclines toward the exit hole and then inclines again towards tha drainage hole.


Another thing with clay dominating soil underneath is that it will give poor drainage under the bottom of the pool, below the concrete shell. This might potentially be important or even dangerous in the future as due to some massive rains or water coming from the pool itself, water may accummulate below the shell creating pressure or who knows what. So, there should probably be a drainage pipe, the one with holes in it, taking that water to a lower place. This is already at pool depth so the canal leading to the place of depositing this water would have to be at least 40 cm deeper at it’s end. Drainage pipe should be mildly inclined and an inground hole filled with rocks would come great at the end of this canal with pipe at its bottom. One great material in these cases is geotextile. I will use geotextile all around the rocks (especially on top) in the drainage hole and also to cover entirely the shell of the pool before concrete as well. This will ensure that soil and organisms don’t overtake empty spaces between rocks in drainage hole for a long time, contributing to deterioration and also taking space that is meant for water from under this pool jacuzzi.


Once drainage canal is done and covered again with soil, and pool shaped hole is finished, it’s time to cover entire shell in geotextile, all the way to ground surface. This will also make it easier to move while creating the double steel armature in the shape of the shell. Walls are planned to be about 25 cm thick on average. I’ll use 8mm and 10mm steel armature creating 2 nets distanced about 10 cm from each other. This will be possible by using 10×10 cm squares made by pieces of 8mm steel bars as distancers, as these will be easier to bend into that shape. These squares will be sporadically placed between two nets and attached strongly by wire, enough to be able to walk on the top of double armature without it losing structure.

First we will create the bottom net by bending steel bars one by one into the shape of shell along each line a bar passes through. Then there is the perpendicular set of bars that we attach using wire to the first set of bars. This way the first net is created into shape of the pool shell. The second net is done the same way along with elevating it by using the 8mm squares, all of the same size, and attaching it all with wire as well. We will have to elevate the entire double armature as well, once it is finished. This can be done by placing equally thick pieces of wooden planks or bricks that can later be taken out through the holes in the double armature.


Pool with jacuzzi now has to be equipped with pool fittings, reflectors for pool lighting, pipes and all those PVC elements that will be embedded into the concrete later. Pool jets have to be tied to armature in a way that they do not touch steel bars as they may be subjected to corrosion of the bars after a long time. This turned out to be quite a challenge because some sort of binding element has to be used. Since regular wires used for tying in armature are corrosive as well, I opted for special non corrosive thin wire. That made it possible to place jets, skimmer and pipes into their place between openings in steel armature. Keep in mind that the final layer adds another 1 to 2 cm to concrete walls in case it will be pool plaster like in this case. Pipes coming out of the pool finish in the place of the future pool engine room.


Now it’s time to define the exact shape of the pool by wooden lining for concrete to be filled into. For that I’ll be using wooden boards, or plywood in this case where the pool is round. Since the inside of the pool is round and walls are not fully vertical, in that part concrete wall will be applied by hand and not by lining. So, there will be no wood inside the pool, only on the external part of the pool above ground around the jacuzzi. Exception is the inside of jacuzzi because jacuzzi walls are fully vertical and fresh concrete can’t be applied there. Also pool fittings in the jacuzzi are a bit more stacked into smaller space. Plywood around both sides of jacuzzi wall will make it easier to fill the walls with concrete. Especially if there are many jacuzzi jets for hydromassage effects or like on this case, venturi jets that make it possible for effects of bubbles along with water stream from jacuzzi jets.


Now the armature and pool plumbing is finished, we can start thinking about making that biggest chunk of work that also has to be done in a fast manner – application of concrete. For the strongest mixture of concrete, a 3 to 1 ratio of gravel and cement can be used, as well as aditives, such as retarders that may for example give you more time for application if it all prolongs, or plasticizers that will give strength to the wall. I used none of those because of general decision to not use any potentially toxic materials unless it can’t be avoided. However, I had to use an additive that will help blend fresh concrete to the semi dried from the day before, applied only locally. Another rule is that the drier the concrete mixture used for application, the stronger the concrete is once it cures. So you should add as little water as possible, and it will make it easier to apply to walls where they are vertical. Downside is that drier concrete makes it a bit tougher to completely fill the holes inside the armature. A vibrator will not help there but what will is to add a bit of finer gravel or sand along with gravel of bigger granulation size. To complete the full size of the pool, it took 6 days, working with a concrete mixer and buckets. Using gunite pipe or several workers it would probably take only up to a day.


As soon as muscle inflammation is over and we can walk again, it’s time to move on to the final finish which is pool plaster in this case. Pool plaster is a subject of itself, but it is very rewarding if done right. Personally, with addition of glass beads it looks better than ceramics. According to some testing I did before applying pool plaster, the best ratio for pool plaster comes to about 1.5 to 1 ratio between fine quartz sand and white cement. Fine quartz sand means really fine, with granulation between 0.063 and 1 mm in this case. Because such fine granulation quartz sand was not available in Croatia, next nearest place was Slovenia. Quartz sand was traditionally not used in pool building until recently. In the olden days marble sand was used and is probably easier to apply, but quartz appears to show better performance when it comes to water absorption, and therefore duration, as it contains more Silica. Pool plaster is even stronger of it contains an additional aggregate, such as glass beads in this case. Glas beads of different colors can be mixed together with plaster in carefully dosed amounts, or they can be simply “seeded” on top. I tried both and it appears glass beads will come out looking better when placed on top, however the minus is some of them will not attach properly and will fall out after some time or during work. The ones mixed into the plaster have to be carefully cleaned on top with a sponge when plaster is dry enough, in order to provide their reflective function. Water mixed with baking soda will do a better job than just water.


Same as in the case of concrete, the rule of the least water possible applies with pool plaster also. It may not be so with professional pool plasters that contain additives, but in this case we also have almost vertical walls to apply this plaster to. With a runny plaster, it will not be possible to do this at all. Pool plaster with no additives dries really fast and this job has to be done in such a manner. Plaster is applied directly on the concrete wall in one or two layers about 0.75 cm thick each. Why two? Because there is no benefit of doing the job in a fast one day operation when there are not at least three people working on it. This would make it much easier and it would be optimal if all of the pool is covered in one go. In this case, it will last for a couple of days. So to properly blend semi dried plaster from the previous day and fresh plaster, there is the first, bottom layer that serves as a step to the second, final layer on top. In that way, pool water will not pressure itself on the line between old and fresh plaster on the first layer. Pool plaster must be worked on heavily using a trowel after the top layer is applied by means of smoothing the surface. Smoothing the surface or troweling is crucial as it will grind the material into place and also make it smoother. It must be done in a rapid manner while pool plaster is still fresh enough to even move. A bad idea is to splash big amounts of water to soften it again, but if necessary, have a water spray ready instead. Large drops of water will only cause trouble as they will collect and remove cement from surface while moving on their path down.


Pool jacuzzi has almost attained it’s final look and the thing remaining is the pool coping all around. Guess what material will we be making that from? Yes, it is the same material as the pool plaster, only placed in molds. Molds are not previously made equally, but one mold will be moved around the entire pool. Only important thing is that mold is empty in the middle and only holds the sides in direction of pool and opposite the pool. I created one by cutting a 5 cm pipe in half lengthwise and connected the two sides by thin metal bars that will lay on the top of pool way while curing. Pool side of the coping should extend out for at least 4 cm to prevent waves from the pool from splashing out of the pool. In this case it is easier to trowel the top od coping as it is naturally horizontal. It is not too big of a problem if pool plaster mix for pool coping contains a bit more water as this surface is not in contact with water all the time.


And here we are, the final step of installing pool equipment is left to professionals, but an engine room can still be done before pool professionals arrive. We just have to connect the pipes from the pool to engine room, and the ones going from engine room to pool and jacuzzi. Generally pool engine room the size of about 2 by 2 meters and at least 1.8 meter high should be enough for any combination of pool equipment. If this tiny house is made from wood like in this case, it should have a strong base, as pool equipment is not that light, especially pool filter when it gets to be filled with water. Pool engine room should also be well insulated for rain, wind, humidity and sound as well.


In this case we have a Hayward main pump, an additional booster pump for the jacuzzi. Pool filter is also a Hayward using glass beads. One addition that makes pool life so much easier is the chlorine generator also know as salt chlorinator used for saltwater pools. This addition will create proper amount of chlorine from salt in pool water itself, therefore avoiding the need to add chlorine directly. This extra cost however, will save you lots of worry in the long run and also quite some money.