Cracked, Moving screed floor

[polkablues]

Hi guys, had 35m2 of sand and cement screed put down in a new extension December 2013, we are just getting round to tiling quotes in.

Problem is where the screed has cracked you can see movement of a couple of mm deflection when loaded. Naturally I'm a little concerned about this, does it mean the whole thing needs to be re done or has any one successfully repaired a similar issue and if so what methods were the most effective?

Construction is as follows
100mm concrete oversite
60mm jabfloor Polystyrene
100mm quintherm PIR
Wet UFH
120mm screed

Thanks in advance

 

[xdave]

I take it you mean 2013, unless you have travelled back in time to try and address the issue before it happens?

Has the UFH been commissioned yet, and if so how long was it left until after the screed was laid? Was the screed fibre reinforced? Was the perimeter laid against an expansion strip? Do you know why the polystyrene was used as well as the PIR? Is the oversite onto a compacted fully-bearing based or onto a floating floor?

~2mm of movement seems like quite a bit, certainly more than I would tile onto without a separation layer/membrane unless you want wobbly or broken tiles, but with a suitable tiling membrane it may not be a problem. Depth of screed on its own is not normally a cause for cracking and I have used as little as 30mm in renovations directly over pipes and insulation where a fibre-reinforced screed was used with latex added. There shouldn't be any major cracks. The only time I've seen that has been when the screed was allowed to dry out too quickly either due to temperatures or the UFH being commissioned too early.

If it was my floor and if you have the depth to lose then you could scrim the cracks and then seal and add a suitable self-levelling compound over the top, leave for a few weeks and then test for deformability. Mapei ultraplan renovation screed is fibre reinforced, suitable for UFH, good for 3-30mm, easy to apply and made in the UK so cost is low. You can add about 20% latex by volume of water (1 litre per bag) to improve the deformability. (Note - ultraplan needs correct mixing to flow properly - it is vital that it is allowed to sit for a couple of minutes and then briefly remixed before pouring.)

 

[polkablues]

I take it you mean 2013, unless you have travelled back in time to try and address the issue before it happens?

sorry - I have changed that now

Has the UFH been commissioned yet, and if so how long was it left until after the screed was laid? Was the screed fibre reinforced? Was the perimeter laid against an expansion strip? Do you know why the polystyrene was used as well as the PIR? Is the oversite onto a compacted fully-bearing based or onto a floating floor?

The UFH was not commissioned until after the cracks formed, however house was centrally heated? the screed was not fibre reinforced, was laid against perimeter expansion all round. we used polystyrene to add insulation and build up the levels. The oversite is onto a compacted base with DPM

~2mm of movement seems like quite a bit, certainly more than I would tile onto without a separation layer/membrane unless you want wobbly or broken tiles, but with a suitable tiling membrane it may not be a problem. Depth of screed on its own is not normally a cause for cracking and I have used as little as 30mm in renovations directly over pipes and insulation where a fibre-reinforced screed was used with latex added. There shouldn't be any major cracks. The only time I've seen that has been when the screed was allowed to dry out too quickly either due to temperatures or the UFH being commissioned too early.

If it was my floor and if you have the depth to lose then you could scrim the cracks and then seal and add a suitable self-levelling compound over the top, leave for a few weeks and then test for deformability. Mapei ultraplan renovation screed is fibre reinforced, suitable for UFH, good for 3-30mm, easy to apply and made in the UK so cost is low. You can add about 20% latex by volume of water (1 litre per bag) to improve the deformability. (Note - ultraplan needs correct mixing to flow properly - it is vital that it is allowed to sit for a couple of minutes and then briefly remixed before pouring.)

Thanks, ill try this. Do you mean normal scrim tape? What would you use to seal the cracks? What brand of latex would you use?

I will post a picture later

Thanks for your help

 

[polkablues]

Images now uploaded

//media.diynot.com/214000_2133.../214000_213346_77869_24624539_thumb.jpg[/img]

 

[polkablues]

Images now uploaded

 

[ban-all-sheds]

Images now uploaded

• 
  

 

[polkablues]

i'm unsure how to make them larger

 

[ban-all-sheds]

Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11

But another time don't bother with the site's own image hosting feature - it's a desperately cumbersome way to do it - a much easier and quicker alternative is to use an image hosting site, e.g. http://postimage.org/ (other sites are available) to upload your images.

Some hosting sites don't allow direct links to the images, and make you use thumbnails, but if so the good ones will provide the code all packaged and ready to paste in.

• 
  

 

[polkablues]

View media item 77866 View media item 77867 View media item 77868 View media item 77869
Thanks for the advice. All images uploaded correctly now

Cheers

 

[limerockconstruction]

I take it you mean 2013, unless you have travelled back in time to try and address the issue before it happens?

Has the UFH been commissioned yet, and if so how long was it left until after the screed was laid? Was the screed fibre reinforced? Was the perimeter laid against an expansion strip? Do you know why the polystyrene was used as well as the PIR? Is the oversite onto a compacted fully-bearing based or onto a floating floor?

~2mm of movement seems like quite a bit, certainly more than I would tile onto without a separation layer/membrane unless you want wobbly or broken tiles, but with a suitable tiling membrane it may not be a problem. Depth of screed on its own is not normally a cause for cracking and I have used as little as 30mm in renovations directly over pipes and insulation where a fibre-reinforced screed was used with latex added. There shouldn't be any major cracks. The only time I've seen that has been when the screed was allowed to dry out too quickly either due to temperatures or the UFH being commissioned too early.

If it was my floor and if you have the depth to lose then you could scrim the cracks and then seal and add a suitable self-levelling compound over the top, leave for a few weeks and then test for deformability. Mapei ultraplan renovation screed is fibre reinforced, suitable for UFH, good for 3-30mm, easy to apply and made in the UK so cost is low. You can add about 20% latex by volume of water (1 litre per bag) to improve the deformability. (Note - ultraplan needs correct mixing to flow properly - it is vital that it is allowed to sit for a couple of minutes and then briefly remixed before pouring.)

I'd agree with this to some extent - seems a weird combo to have jablite and PIR - and a very thick coating of screed, i've never seen this amount specc'ed before?!

 

[polkablues]

I take it you mean 2013, unless you have travelled back in time to try and address the issue before it happens?

Has the UFH been commissioned yet, and if so how long was it left until after the screed was laid? Was the screed fibre reinforced? Was the perimeter laid against an expansion strip? Do you know why the polystyrene was used as well as the PIR? Is the oversite onto a compacted fully-bearing based or onto a floating floor?

~2mm of movement seems like quite a bit, certainly more than I would tile onto without a separation layer/membrane unless you want wobbly or broken tiles, but with a suitable tiling membrane it may not be a problem. Depth of screed on its own is not normally a cause for cracking and I have used as little as 30mm in renovations directly over pipes and insulation where a fibre-reinforced screed was used with latex added. There shouldn't be any major cracks. The only time I've seen that has been when the screed was allowed to dry out too quickly either due to temperatures or the UFH being commissioned too early.

If it was my floor and if you have the depth to lose then you could scrim the cracks and then seal and add a suitable self-levelling compound over the top, leave for a few weeks and then test for deformability. Mapei ultraplan renovation screed is fibre reinforced, suitable for UFH, good for 3-30mm, easy to apply and made in the UK so cost is low. You can add about 20% latex by volume of water (1 litre per bag) to improve the deformability. (Note - ultraplan needs correct mixing to flow properly - it is vital that it is allowed to sit for a couple of minutes and then briefly remixed before pouring.)

I'd agree with this to some extent - seems a weird combo to have jablite and PIR - and a very thick coating of screed, i've never seen this amount specc'ed before?!

The building inspector suggested extra insulation to build up the levels rather than paying for concrete, pay for insulation, the more insulation the better?

I re checked the thickness and its more like 70mm of screed.

I have now had the suspect screed ripped up and having a liquid screed to replace

thanks for the replies

 

[jeds]

It's not good - but probably wont cause a problem once tiled. Try a fine crack sealer first to see if it stabilises the movement. If it does tile with a good quality separation membrane under the tiles.