humps in our tiled floor from sunlight?

dimanche 2 novembre 2014

hi guys, at the front of our house, we have a indoor tiled area around 5x2m that used to be part of a veranda but has since been enclosed. the tiles are on a 25mm concrete compressed slab, the slab sits on the joists, i can see this clearly as there 6ft access where the car goes under the house.

so theres a patch of strong sunlight that hits an area of about 1.5 x 1.5m straight outside our front door at a certain time of day, it gets quite warm and this tiled area swells / humps up around 5mm, possible more. this results in the front door only being able to open half way until it grinds against the tiles. but.. i also noticed swelling in winter time too and late at night.

my question is, can a tiled concrete slab warp like this? or is it most likely an issue with the joists?

when i look under the house, betweeen the joists its clear that the concrete is raised considerably between the joists. you can also see in the pictures that the screw looks to have been pulled through the compressed slab. is compressed sheet prone to warping with heat?

the joists below are a bit of a mess and have a lot of patching and repair work.. we have only had the house a year so i dont know much about its history.

the image below shows our front door and the problem area which is directly in the middle of the lit area.

the image below is directly under where the door opens (the problem area)

the image below shows where the compressed ocncrete sheet has pulled away from the joist.

so on the far left and right side of the image below, the slab sits flush with the compressed slab, but in the centre, marked with a circle, the slab humps up with a gap of around 8mm.