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Submit plansI have an existing indoor swimming pool that I would like to fill in so that I can use the space as a floor to a dwelling. I am unsure what method to use. The measurements are 6.7 x 2.9m and the average depth is 1.2m. The pool has a plastic liner. I suspect concrete pillars support the base so think I will have to take the base away and level with aggregate. I contacted a structural engineer who drew up a specification with steel and wooden beams to board over the pool. While this appears cheaper than fi lling with concrete, the labour costs would be higher. The floor base would be hollow and, as such, may be
noisy when walked over. An alternative is to fill with concrete footings and finish with a 100mm- 150mm fl oor slab mix RC35, a total of 24.6m³. I do not know if I would need steel mesh reinforcement. I am a little worried about the possibility of voids in the concrete (Self-build Diary, Build It, July 2006). I was told the concrete would settle over two to three years and the floor would require a screen. Is this right? The other suggestion is to fill with aggregate in stages, whack it down and then top with the floor slab mix. I was thinking of laying floor tiles as a finish.
If you fill with concrete, don’t worry too much about any possible voids as it is not a structural element – it is only going to be a floor. The additional weight in the pool area could generate some settlement for a few months. But, in general once it has set, you should not get any shrinkage; if concrete continued to shrink, most dwellings would be affected If you use hardcore, you should compact the fi ll every 150mm, but as you are fi lling over 1,200mm you could still get some settlement in years to come, and this would be more noticeable on a tiled floor. As an alternative, look at installing timber joists off masonry hangers around the pool perimeter on the 6.7m sides so that you have short span joists. Use a sound-proofing material on top of the joists and then cover that with a sheet material over the whole floor, so that the tiles will not have a joint to deal with where the existing floor and covered area join.
