Do I need an expansion joint?

[FreeD]

External flat roof/balcony refurbishment. All tiles have been lifted - cleaned and relaid with BAL fastflex - substrate fibreglass. Joints 10-15mm. Area 15m2. There was no expansion joint before...should i put one in? fill one of the joints with Silicon?

Also instead of finishing round the edge with grout (large areas to fill) I thought about using sand/cement 6 to 1 with SBR for flexibility - sponge to finish what you reckon?

Thanks

 

[Gazzer]

I dont see a need for an expansion joint unless there is one through the substrate, which I am assuming there isnt.
As for the perimeter I would be inclined to fill the joint with foam ( Everbuild Joint Backer Rod 8mm - £0.25 - www.protilertools.co.uk ) and top off with Silicon.

 

[Gazzer]

Sorry I re-read and saw you have large areas to fill. Then maybe your way would do. Rather than flat fill though I would use a bottle finish ie a curved finish to push water away from the wall and onto the floor.

 

[FreeD]

Yep thats what i'll do. Think it will look good. No expansion joint in substrate.