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Sulphate Attack in Concrete Floors - How Much?!?!


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#1 Guest_Paul Haines_*

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Posted 27 August 2003 - 07:38 PM

A structural survey advised that 'sulphate attack' had occurred to the concrete floors of my house. The recommendation is to dig up all the floors and relay them. I have only had 1 quote for over £5,000 (area approx 40 m2), not to mention the mess (ripping out the kitchen etc) and the fact that the house will need to be empty while this work takes place!
Does anyone have any experience of this problem? Is it common? Does it really need to be put right? Is digging up the whole floors the only option?

#2 eddie

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Posted 28 August 2003 - 08:25 AM

new one on me, sounds like there is no DPM under the concrete, therefore they really need to be replaced or a waterproof surface put down. problem is, that if you have really got sulphate damaged concrete, it will eventually crumble into dust... What does this 'sulphate attack' look like?

#3 Guest_Carl Pennick_*

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Posted 29 August 2003 - 12:06 PM

You could think about applying a flooring membrane such as Oldroyd Xs and then pouring a new screed over the top.

#4 Guest_Paul Haines_*

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Posted 30 August 2003 - 03:23 PM

Sulphate attack syptoms on my floor, show as a floor which rises slightly toward the centre, with some surface cracking (the concrete itself appears solid and sound). Apparently it is caused by a chemical reaction between the hardcore and the concrete which causes the concrete to swell over time. But the concrete has been there for over 70 years and you wouldn't know it is not level without putting a spirit level on it. We have owned the house for 20 years, and I was not aware of the problem until it was pointed out to me. I want to sell the house, hence the structural survey and I just needed to know if digging up and relaying the floor was absolutely necessary. Thanks for the ideas - any more ideas/thoughts would be appreciated. Has anyone out there experienced this problem?

#5 Guest_Concrete King_*

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Posted 31 August 2003 - 10:57 AM

Sulphate attack is one of the most common aggressive actions leading to the deterioration of concrete. The large number of concrete structures that have degraded prematurely over the last forty years has shocked structural engineers who had previously been of the opinion that reinforced concrete was maintenance free. Concrete can be affected by a chemical reaction involving sulphate that when present in contaminated hardcore along with a source of moisture, reacts with cement present in the concrete causing it to expand and crack.

The force of the chemical reaction can displace external and sleeper walls on domestic and commercial buildings leading to the opening of skirting board joints, the bouncing of timber floors, cracking and displacement of the brickwork as well as disruption of concrete floors and sub floors. The physical defects described can take up to 10 to 20 years before they become evident. The correct remedial actions to sulphate attack is normally to remove all the defective concrete and contaminated hardcore and replace them which is a disruptive and costly process. Building insurance does not usually cover sulphate attack, as most policies tend to have a clause that exempts all forms of chemical attack.

Concrete footings and foundations can be subject to deterioration from chemical attack from acidic solutions or salts of sulphate. The risk is increased in areas of previous mining activity where the concentrations of minerals in the soils pose an increased risk. Rainwater absorbs carbon dioxide from the atmosphere forming carbonic acid that decomposes - in situ- the sulphides concentrated from mining waste to produce sulphates. The sulphates react with cement within the concrete before causing gradual degradation and eventual failure of the concrete.

Concrete King

#6 karen

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Posted 24 March 2004 - 02:19 PM

I have recently had a sulphate content test on my kitchen floor as i believe it has suffered a sulphate attack. The test was conducted to the slab and sub - floor materials, and the results were as follows:
SO3 & SO4 levels were found to be 0.01 & 0.13 respectively. I was advised that these levels are well within acceptable limits and therefore could not possibly cause a sulphate attack. I'm not convinced! Can anyone shed any light on exactly what levels are needed to cause a sulphate attack?

#7 Guest_iantrader_*

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Posted 07 April 2004 - 06:25 PM

Does anyone know if this sort of damage will or should be covered by building insurance?

Ian

#8 Guest_dave leese (Unregist_*

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Posted 14 August 2004 - 08:07 AM

i am at this moment having my entire floor
replaced because of ash grade B but the builder
who is doing the work has dug out 600m deep and
has left the ash under the divide walls and fireplace also he,s put the old concreate back in
this can,t be right or is it
any help a.s.a.p dave@gb59056.freeserve.co.uk

#9 Guest_richthemix (Unregist_*

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Posted 14 August 2004 - 09:23 PM

Is the old concrete going back in as hardcore,blinded, then covered by visqueen?

#10 ericc

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Posted 14 March 2005 - 08:47 AM

Hi All, at the moment I am looking to purchase a house and the survey has shown that part of the dining room wall has suffered from Sulphate Attack. The vendor has documentation (diagnosis by a surveyor and repair by a builder) to say that it has been treated and the problem resolved however is this the sort of thing that will come back to haunt me in the future ? ie if there was a problem with one floor could it rear its ugly head elsewhere or is it just a case that we may never have a problem again ? I just want to protect my investment ! :-)
Thanks for any info that you can provide !
Eric

#11 bobg

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Posted 14 March 2005 - 12:38 PM

The only real treament for it is removal of the crete.
There must be moisture present for the reaction to take place so its unlikely itll affect upper floors but not impossible.
It would probably be best to ask your soliciter if the surveyor would be liable should it reoccur where he says it was remedied but then theres always the chance of it opping up elsewhere.
As for the ground floors,it happens when moisture and sulphates in the hardcore react with the concrete,one would have to suppose theres the same hardcore under the whole house therefore only one area being affected is unlikely in the long t5erm.
the problem is that if its the slab it can lead to your walls being unsupported and a bigger problem being that testing is destructive and expensive.
Id have at min a full survey done with particular note being made of the sulphate problem by your surveyor and see what he says.

#12 ericc

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Posted 14 March 2005 - 12:56 PM

Many thanks Bob - the surveyor suggests that the cause was the fact that the dining room used to be the kitchen (before it was extended) and they are claiming that the Catalyst was the washing machine being in the kitchin previously. He thinks its just a rogue batch of cement but I dare say he cant be sure. I guess if the whole house could be based on it I suppose itd be like living on a potential time bomb ?

#13 bobg

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Posted 14 March 2005 - 05:04 PM

Rogue batch?Lol.
Look here;
http://www.alanwood.co.uk/strsurv_sulphate.htm
Itll give you an idea and save me typing it out.
His suggestion though possible is vv unlikely.
Sad as it is I woouldnt buy,theres a good chance alls ok but theres plenty of houses on the market and Id have to think is it worth the risk?
My sympathys are with anyone who has the problem but at the end of the day thats not what your asking,youve got to weigh up the odds and in this case Id err on the side of caution unless its your dream home and no other will do then maybe its worth the risk

#14 Guest_johnbirksjfslifecouk_*

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Posted 02 June 2005 - 04:17 PM

sulphate test is referenced to bre 363 which is applicable to new build only and was removed from publication in Jan 2002.
It was replaced with sd1 which states "the sulphate test is not to be used as a method of assesment in the risk of sulphate attack to a concrete floor"
The correct method to replace a concrete floor is to remove the concreter and lay a membrane.tHIS IS REFERENCED TO BRE 322 DATED 1997 Floor and flooring repairs Pye and Harrison.
The key elements are if the hardcore is dry and a membraine is present the concrete will not be attacked by the red ash or sulphates.
Reference Building Regs 1965 and the requirement to insert a membrane.
So if the property was built after 1965 it had a membrane and if it was laid properly the likely hood of sulphate attack would be extreemly remote.
For further reference go to the UK PARLIAMENT SITE TYPE IN RED ASH "joan Walley question to Mr Hope minister of building etc"
We wish to hear from any one who has had there property valued at £1 due to red ash or been forced to have there floor dug out on a valuation particularly if the house was built after 1965 and you are resident or live near to North Staffs.
We have found this out as the valuer insisted we provide a guarantee from a local expert.
Our floor sank by up to 11/2 inches after the work was completed and the floors relaid with laminate the work carried out was as per dave leese describes.
thats how we know all the bre stuff we did not need it doing and this comes from 2 structural engineers and trading stds.
WE NEED TO HEAR FROM ANY ONE ELSE WHO HAS SUFFERED THE SAME FATE TO COMPARE NOTES ON VALUERS AND CONTRACTORS.

#15 louiset1974

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Posted 21 April 2006 - 09:29 AM

I am looking at purchasing my 1st property and the valuation survey has noted that "houses that were built in the era of 1050's/1960's sometimes had defective "fill" materials in the concrete. As the vendors are not authorising me to have a sulphate test done on the concrete, where can I find information relating to what year and what materials were used in the concrete when the house was built. your views and advice would greatly be appreciated!

#16 Guest_buildersmate_*

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Posted 21 April 2006 - 11:46 AM

Well it sounds suspicious that they won't let you spend your own money on having the necessary survey done. Draw your own conclusions? The only way I can think of to find out if there is a LIKELY problem would be to try and find out from other properties in the area, built at the same time (if its on an estate).

#17 bobg

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Posted 21 April 2006 - 01:06 PM

You cant find out for sure without a test.It could be the substrate that causing it,it could be just a bad mix and will onlybe in 1 tiny bit.
If they wont let you test then Id walk away.
It doesnt matter what year it was built and your never going to get the mix sheet from concrete 50 yrs ago.

#18 Guest_cwatters_*

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Posted 21 April 2006 - 05:43 PM

Rather suspicious that they won't let you get a test done. If it's a semi or a terrace try asking the neighbours if they had one done...but I'm not to optimistic. I'm sure many people get a survey done then never read it.

I think some of the fillers used included slag and ash from iron works and coal fired power stations. Some ash fillers are actually ok I believe.

#19 louiset1974

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Posted 24 April 2006 - 06:38 PM

many thanks to all that I have commented! I believe it was "fly ash" or "coal ash" what was used... I have taken the plunge and have decided to go ahead with the purchase after speaking with other home owners on the road, they have never come accross a problem! I am however going to have the test done myself as the vendors have agreed to pay half towards the costs if it comes back with a bad result! something I suppose! Thanx again to you all!!!

#20 appleblossom

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Posted 14 September 2006 - 01:48 PM

Having had the test done and the property surveyed by a structural engineer who declared the foundations healthy our house suffered sulphate attack requiring us to move out for several months while the repairs were carried out. Our insurers refuse to meet the cost stating that it is "chemical" attack and therfore not covered. We are considering taking legal action against the surveyor who got it so wrong. has anyone successfuly done this. Would appreciate any words of wisdom.