Adding extra sleepwall in breeze block on concrete floor, without mortar?

[compact]

In the Kitchen, there is slight bounce on the kitchen floor we want to tile.
The joists are the existing smaller ones from the 70's (I guess), with new 18mm tongue and groove chipboard flooring screwed and glued.

The old floor seemed ok, we took it up to make level after knocking through and now we have the bounce. I've managed to get into the very small crawl space (smaller that the rest of the house, most an army wriggle, then crawling).

My plan is add extra sleeper walls under the joists to support and eliminate the bounce.
As the space is so tight I was planning on two breeze blocks with a brick and some slate (with a DPM) sitting on the flat concrete oversite. If packed in tightly, would you say it is ok not to use mortar?

Thanks

 

[Notch7]

In the Kitchen, there is slight bounce on the kitchen floor we want to tile.
The joists are the existing smaller ones from the 70's (I guess), with new 18mm tongue and groove chipboard flooring screwed and glued.

The old floor seemed ok, we took it up to make level after knocking through and now we have the bounce. I've managed to get into the very small crawl space (smaller that the rest of the house, most an army wriggle, then crawling).

My plan is add extra sleeper walls under the joists to support and eliminate the bounce.
As the space is so tight I was planning on two breeze blocks with a brick and some slate (with a DPM) sitting on the flat concrete oversite. If packed in tightly, would you say it is ok not to use mortar?

Thanks

If its a suspended floor, do you have a proper oversite or just some concrete laid on uncompacted ground to blind off soil? I dont know what is likely or how stable it will be. Im sure somebody will be along to advise

You could sister the existing joists as an alternative, screw and glue 8 x 2

For tiling you want lots of screws. Ditra mat for decoupling.

 

[compact]

The over site is pretty thick , as we dug through some foundation of new steel.
Can't sister without taking up the floor, if I was to do that I would lay new joists.
Ditra is good for lateral but doesn't protect for bounce. Though I will be using it as going wfh across the room which straddles both this timber and concrete slab

Cheers

 

[Notch7]

The over site is pretty thick , as we dug through some foundation of new steel.
Can't sister without taking up the floor, if I was to do that I would lay new joists.
Ditra is good for lateral but doesn't protect for bounce. Though I will be using it as going wfh across the room which straddles both this timber and concrete slab

Cheers

In that case I would say no mortar would be fine. If you wanted you could use spray adhesive and or a glue from a gun like CT1

Im not sure about slate. I think plastic shims or some wedge packers maybe.

 

[compact]

I tried a few columns, with heavy concrete blocks and slate in a 35cm space....
It didn't really work as ever time you pack in slate it raises it slightly, as the whole floor is tied together.

I have gone for the simpler, screwing legs into the side of the joists every couple of feet.
This has worked and made it solid

Cheers for the replies

 

[foxhole]

These are a simple strong solution
https://www.metrofixings.co.uk/main...MI4_XQv6Kv2gIV6pztCh1Q9wTmEAQYASABEgJYKfD_BwE

 

[compact]

Hi @foxhole those look great, however they don't go high enough and are a little more expensive that screwing multiple 2x4x35 lengths into the joist.
I can't wait for this job to be finished..

 

[Mr Chibs]

What legs did you use?

 

[compact]

@Mr Chibs
I screwed lengths of 2x4 into the sides of the joists every couple of feet.
Slight overkill, but no bounce and no lifting (from the slate packing) and should last well