Movement joints in concrete slab.

[MarkH]

Our slab is devided into a 4.8m by 10.5m section and a smaller 3.8 by 6.3 part. The architect long ago suggested two transverse movement joints in the large section but my dad - the ex-cowboy builder - reckons there's no need.

 

The slab is 100mm, steel reinforced.

 

My research so far suggests the easiest route would by to use a 'groover' to cut a partial depth joint in the top 25% of the slab (before it is fully cured). Am I on the right track?

[PeterW]

If you are putting UFH pipes in it then be very careful about movement joints. 

 

Suggest they go under a wall if you do put them in and then make sure there is sleeving where the pipes go through the doorway. 

[IanR]

What's the reason your architect wants to split the slab? 

 

Mine's  25.5m x 18.5m and was cast without joints. 

[MarkH]

42 minutes ago, IanR said:

What's the reason your architect wants to split the slab? 

 

Mine's  25.5m x 18.5m and was cast without joints. 

 

Was yours reinforced Ian?

[Oz07]

Conventionally it's just there too control cracking. You might get away without if steel reinforced. I put them in at every weak point. Doorway etc. Also try and split tiled rooms with the direction you will be tiling. 

 

If theres no ufh then no reason not to put in for how long they take

[ProDave]

The house I am wiring at the moment has the floor slab cast as one, with no expansion joints.  There are two large cracks visible in the slab, and not at the points where you would think was a "weak point"  As he is planning to polish the concrete and varnish it, an expansion joint or 2 would probably have been better than 2 cracks.
 

[IanR]

50 minutes ago, MarkH said:

 

Was yours reinforced Ian?

 

It is, 100mm thick (+ ring beam) mesh reinforced, with UFH, installed over EPS.

 

 

We've got a couple of small surface cracks, but as we didn't have plans to polish weren't concerned about the risk of minor cracks.

Edited September 16, 2016 by IanR

[duncgee]

Are there any concerns regarding air tightness if the floor slab cracks?

[MarkH]

12 hours ago, duncgee said:

Are there any concerns regarding air tightness if the floor slab cracks?

I guess the dpm takes care of that.

 

[Oz07]

13 hours ago, ProDave said:

The house I am wiring at the moment has the floor slab cast as one, with no expansion joints.  There are two large cracks visible in the slab, and not at the points where you would think was a "weak point"  As he is planning to polish the concrete and varnish it, an expansion joint or 2 would probably have been better than 2 cracks.
 

Theres also maximum bay sizes with certain types of concrete. The agilia mix I usually use for instance. Like you say, a neat saw cut following on from a nib or wall, or in the centre of a room looks proper, a wonky crack doesn't

[Oz07]

i wouldn't worry about it if it was being covered and has reinforcement.