# Forum Home Renovation Flooring  Magnesite flooring. Any ideas?

## villageidiot

My concrete slab floor is coated in a 10-12mm layer of a cork like material which I have since learned is called magnesite. apparently it was used in the 1960s to level concrete slabs and provide sound insulation. 
It is very porous and I have read about the problems caused by it getting wet and reactions with the reinforcing in the concrete underneath etc. In fact it is so porous that if there is a lot of rain the magnesite absorbs moisture from the air, you can almost see the magnesite changing colour as it absorbs the moisture and gets almost damp. 
I was wondering if I should seal the magnesite with Bondcrete to help prevent this? Later I will be laying a floating laminate floor over the magnesite. I may also need to level the magnesite prior to laying the floating floor with a strong cement/sand mix or self levelling cement and I was thinking that the Bondcrete would be good to have not only to seal the floor from any future spills or the humidity in the air, but also to help the cement-sand mix or self levelling cement stick to the magnesite better. 
Thanks for any advice.

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## Larry McCully

Howdy there, i know of the stuff you are talking about. I did a small job on the northern beaches and the existing floor had it on it. I also had to level out the concrete prior to installing a timber floor over the top. I found it nessery to remove the substance so thati could get a good firm foundation first. It came up very easly and i was then able to give the concrete a grind then applied a primer then the leveling compond. In your case, there is no reaqson why you cant seal the magnesite with a bonding agent then spred a leveling compond out to get the level you require. However just bear in mind that your leveling will only be superficial only, and it wont have a perminate bonding  to the magnesite. Eventually the adhesives will break down and seperation in the mag will occur. Also it may be susupable to fracture , the mag may have a flex ability in it and the leveling compond may fracture. Leveling compond works best when the substrate is solid and firm. But if it is only intended as a tempory application then have a go at it. I myself would remove all traces of existing componds and start from scratch again.

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## kevvy

I have the same problem at my unit previously, when I removed carpet , tiles and discover magnasite so I made some research.  
As Magnasite cause concrete cancer ( the steel reforce between concrete would rusting out ) so I use light duty jack hammer ripped off magnasite to concrete slab level quite easy. 
Put sand/cement mix all over the concrete slab to the correct level , lay soundproof underlay then install floating timber floor. 
I am pleased with this result. 
I assume you are living in a unit , if so please check with strata before lay timber floor as some strata wont allows timber floor.

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## Bloss

Search 'magnesite' on this forum and you'll get some more info. eg: http://www.renovateforum.com/showthr...ight=magnesite  and http://www.renovateforum.com/showthr...ight=magnesite  :2thumbsup:  The initial posts on these threads seem curiously similar even though ostensibly from different members . . . :Confused:   :Frown:  
BTW - magnesite does not 'cause' concrete cancer which is due to most often to reinforcing steel rusting and expanding as it does so causing various effects such as spalling that are together called concrete cancer. The steel rusting is most commonly due to: poorly treated reinforcing steel being used in first placethe ends of reinforcing being too close to the surface allowing water to seep through concrete and react with the steelincompatible metals being used on the steel causing a galvanic reactionfractures in the concrete allowing water to penetrate the concrete and react with the steel
Concretes that are too alkaline can also be triggers as they combine with moisture and CO2, create surface cracking that enlarges and deepens allowing more moisture ingress and so on.

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## villageidiot

I dont really want to have to rip up the magnesite. There are a few reasons for this. 
1. If I rip up the magnesite I will have to do the whole unit to keep the levels right and I am only laying the laminate floating floor in the lounge, kitchen and hallway. 
2. The magnesite flooring in a unit is actually a body corporate issue. I dont actually own the magnesite or the concrete slab it is laid on, only the floor coverings such as carpet etc. The floor is regarded as common property and I dont think I would be allowed to rip it up. 
3. I have a linen cupboard coming off the loungeroom that has no magnesite on the floor of it, and therefore I can see the concrete slab in that section, and there are a lot of dags and lumps and bumps in the concrete there, VERY uneven, much more uneven than the magnesite itself!  If the whole floor is like this then it will be a lot of work to get it level. 
4. I have had a few people come to quote for the floor and they all say the magnesite on my floor is in good condition, not drummy or lifting as they have seen in other places. 
Would the Bondcrete seal the surface and stop the magnesite absorbing the moisture from the air? If it does, that would only be a good thing wouldnt it? 
Would using Bondcrete to seal the floor help the strong cement sand mix I plan to use for the levelling stick to the magnesite better? And finally could I also add some Bondcrete to the cement sand mix itself to make it stronger? I know self levelling cement would be more ideal for the levelling, but at around $40 a bag I thought i could use a strong cement/sand mix with Bondcrete added to the mix and scree it over the low spots.

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## Gaza

two options, 
lay builders plastic down before laying flooring tape all joints and up turn it up the walls under skirting. 
or 
use paint on membrane such a polyurthane, check with manufacter first to ensure it bonds. 
bondcrete is PVA glue and is used as a sealer before applying render it is not a full waterproof coating.

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## That Floor Guy

If you're determined to leave the magnesite then the only leveller I'd use would be Arditex by Ardex (prime with Ardex 51) 
Arditex is a "flexible" leveller that is mixed with a latex solution rather then water. As long as your magnesite remains sound you shouldn't have any issues. 
As mentioned prior to installing your floating floor it's always a good investment to put plastic down.  
I know the price of levellers hurts initially, but I've seen the results of people tempted by the cheaper sand and cement option for levelling over unsatisfactory substrates, it aint pretty.

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## Bloss

> If you're determined to leave the magnesite then the only leveller I'd use would be Arditex by Ardex (prime with Ardex 51) 
> Arditex is a "flexible" leveller that is mixed with a latex solution rather then water. As long as your magnesite remains sound you shouldn't have any issues. 
> As mentioned prior to installing your floating floor it's always a good investment to put plastic down. 
> I know the price of levellers hurts initially, but I've seen the results of people tempted by the cheaper sand and cement option for levelling over unsatisfactory substrates, it aint pretty.

   :What he said:   :Arrow Up:   and as Gaza said Bondcrete is not a bonding solution to improve the bond between cementitious surfaces that are of different types or ages so a specific purpose sealant is best. But if as you say the magnesite is sound then it should cause you no worries.  :2thumbsup:

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## wildfire

Ive just bought a unit and have just started renovations and have found that I also have magnesite under a cork floor, under a vinyl floor in the kitchen. Im wondering where to stop pulling it up. The concrete I have in my unit is very smooth and flat under the magnesite, is it a big job to pull it up? Im on the botton floor so I dont think sound would be a problem. Was it just standard to put this material down in the 1960's?

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## Larry McCully

The material was used at that time as a leveling solution and as well as a bedding to gain a required height. it is not worth retaining it at all as it will deteriorate as time goes by, My recommondation is to completly remove the substance to the slab, and if you need to level fill or you may require height, then use a cementious leveling compond as Adur z8 or k15. This way you will have a perminate substrate to work with.

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## Bloss

:What he said:

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