Suspected inspection chamber under the conservatory

[griffta]

Hi,

Recently we've found a large (1m x 1.5m) section of our tiled conservatory floor has begun to 'bulge' up. The hump wasn't noticeable at first, but over about 3 weeks, it's become very noticeable, with an estimated difference of 1-2cm across the area. When we tread on the area, it sounds hollow and flexes. Oddly, the grout of the tiles has not cracked.

The conservatory was added to the house 20 years ago, long before we owned it. It's an odd construction because the land slopes greatly across the width of the house, meaning that one side of the conservatory floor is built up from ground level with an odd curved retaining wall. An inspection cover is adjacent to the retaining wall at ground level; one gully appears to be going right under the retaining wall and the conservatory.

Having run a camera up the gully, it shows the pipe entering a large open enclosure at a distance which would correspond exactly with the raised tiles. Therefore, I'm sure it's an inspection cover that has been boarded over with (possibly) plywood. I guess this has swelled and is pushing the tiles up.

Please see the photos below.

Anyway, I'm really concerned about this. Could anyone suggest what could be done? Could this be something buildings insurance would cover?

Any help or advice would be greatly appreciated.

Matt.

 

[martygturner]

Fit a recessed gas tight manhole cover, they take tiles and are lifted by two keys.

eg

Wrekin C271M/060045 Double Seal Recessed Manhole Cover & Frame 600mm x 450mm - 10 Tonne | Drainage Superstore®

Double Sealed Recessed Manhole Cover and Frame 600 x 450mm from Wrekin. (C271M/060045). Order Helpline ☎ 01752 692 221

www.drainagesuperstore.co.uk

 

[Notch7]

I guess you need a multi tool or thin disc cutter for a mini grinder, cut through the grouting and see if you can get the tiles up without breaking them, then find out what the issue is.

I wonder what the construction detail is here - giving the Cons is much higher than ground level, so its probably got a suspended floor. If so there would be a void under the Cons with the inspection chamber coming up through the void.

I wonder if the inspection chamber base is bedded on a bit of concrete and this wet weather has forced the inspection chamber to rise, pushing up the tiles. In which case when we get dry weather it might go back down.

 

[noseall]

Hi,

Recently we've found a large (1m x 1.5m) section of our tiled conservatory floor has begun to 'bulge'

Could also be sulphate attack...?

 

[griffta]

Thanks for all the advice. I think getting the tiles up and building the sides up in brick with an airtight lid, as martygturner suggested, seems like a good option. It's probably too big a job for me to attempt, but I have ordered a better inspection camera to confirm the details before I appoint a builder.

this it money that I'd rather have spent on better things, but such is life!