Filling the gap between pier and floor

[DIYman]

Hi all. I have a query about making he gap between the pier and the concrete floor of an observatory moisture proof. A friend suggested once the concrete pier is poured and has set, wrap the sides that will go through the floor with styrene foam panel. (This will be easy as the base of my pier will be square.) Once done, the floor can then be poured.



If I do this, I was told to either leave the styrene in place or dissolve it out using a solvent like petrol and fill the gap with some type of soft setting mastic.



What are your thoughts on this?

[Gordy]

The styrene (I think you mean polystyrene) idea sounds great. You could always leave it there permanently.

[Imme]

Why not just use expansion gap foam..... it’s made for the job.

[Wilso]

Sounds pretty good to me!
Just keep it to 1 layer neatly at the top before (you can cut away excess later) and then sikaflex the joint later on. Should be plenty of tips on you tube if you haven’t used it before.
Good luck:thumbsup:

[glend]

I used expansion gap foam, has worked well for six years now. I would not use Sikaflex, it can make a mess unless you know how to use it.