Moisture resistant MDF - advice please????

[DHTiling]

Kerdi is a faster tanking method......you can tile onto it as soon as you have applied it ( as long as you use rapisetting adhesive to apply the kerdi)..
And kerdi is not expensive..only about £7 a sqr mtr.....where as tanking kits ( soloutions ) are about £40 for a kit to tank about 3 to 4 mytrs and need to dry before tiling......just a thought mate.....lets us know how you get on...
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Soz gazza mate. ..Don,t use whitestar etc on top of kerdi..takes to long to dry....use cement based adhesives only......

 

[protilers]

If you use Daves suggestion yes,you can use white star...personally I would just take MDF boards off and replace with backerboards...then standard tank the joints...much cheaper, re- use MDF on a coffe table or rabbit hutch or summat

i am still wondering how you are going to fix the kerdi to the mdf...........mosaic fix?..... is that not for mosaics? extra white etc.......

this situataion is wrong because of the mdf......fixing the problem has gone off the radar..........and out of your bank balance, MDF = no good......ever..... to save everyone money and for you to get the job tell builder/customer remove unsuitable substrate and replace with a suitable one..... lets face it......no one ever blames the builder for his prep, all they say is our tiler is a...........(put own favorite profanity here!)......good luck!

p.s bucket adhesives are only good to a professional tiler for one reason.........4" ceramics in a kitchen splashback.....and even then the customer had to have supplied it!!!!!!!!!!!!!!!!!!!!!!!!

 

[Daz]

I'm supposed to be starting the job on Monday so getting the builder back in could be an issue. I'm gonna take a look at what he has done tomorrow and see how much work is involved in ripping out the MDF.

On the tanking front, the Tilesafe tanking that I have used has a very aggresive universal adhesive and sticks like the preverbial to a blanket. I may suggest this to my customer but will make a, now, informed decision tomorrow.

 

[DHTiling]

We know the MDF is not the best substrate for bathrooms but tanking will do the job ..as for kerdi...you use a rapidsetting flexi cement based adhesive..it will set before moisture from adhesive soaks into MDF...

Ripping the whole lot out will cost the customer a packet...we are trying to offer an easy option here not full re-fit......

god luck captain slow and let us know how it goes..........

 

[protilers]

We know the MDF is not the best substrate for bathrooms but tanking will do the job ..as for kerdi...you use a rapidsetting flexi cement based adhesive..it will set before moisture from adhesive soaks into MDF...

Ripping the whole lot out will cost the customer a packet...we are trying to offer an easy option here not full re-fit......

god luck captain slow and let us know how it goes..........

dave with all due respect......i do not know of an adhesive (even s2) that a manafacturer will reccomend to stick to mdf in wet areas, even if its (just) sticking kerdi....the important fact here is the expense.....even if you have to pay a carpenter to come and remove the mdf ad replace with 18mm ply ...£150 (example) per day @ 1 day.......
captain to tank at (example) £150 per day @ 1 day

total prep = £300


plus 18mm ply 8" x 4" ft @ £40 and tanking @ most expensive bal wp1 = £70


all in £410..........and no leaks and no problems.....do the time and motion calculation, any other way costs more and has more chance of failure due to multiple substrates flexing against each other! IMO.

p.s you will not have to rip it all out......just the mdf.......fein multimaster.....mmmmm

 

[DHTiling]

Lee..as you say adhesive manufactures will not guarantee there adhesives on MDF in wet area's...but that is if tiling onto MDF...If kerdi was used onto MDf then no moisture can penetrate it..thus no problem with delamination or swelling.....that's what tanking membranes are for....I know what you are saying about tiling onto MDf and yes you are right....but using a tanking membrane or similar will do the job no probs......and so will ripping the whole lot off and using backerboards....

 

[Ric]

brill post, very interesting lads, i have bath panel to tile (mdf) with mosaics and was going to use mosaic fix as it says you can as long as not primed , but, it also says dry internal areas. Didn't really want to board over the top as i think it would bring the tile out too far, the kerdi option looks good can u buy as little as a square metres worth?

 

[DHTiling]

brill post, very interesting lads, i have bath panel to tile (mdf) with mosaics and was going to use mosaic fix as it says you can as long as not primed , but, it also says dry internal areas. Didn't really want to board over the top as i think it would bring the tile out too far, the kerdi option looks good can u buy as little as a square metres worth?

You certainly can rik mate......You will get it at CTD.....

 

[tiler burden]

this is why tilers should prepare and advise on substrates when it affects the areas they tile.

general builders are a pain in the r's. i totally agree that there is no way that green mdf should be used in a continual hot/wet area. ok the tanking will prevent water penetration, but moisture can build up behind the tanking area due to condensation and eventually break down the mdf. maybe not in a years time but it can and does happen. australian and american tilers will vouch for that..

any area that has extreme variations to temperature changes can be affected by condensation..if you have ever worked on loft conversions you will realise that the plasterboards in the loft need to have a foil backs to there underside and there has to be a vapour barrier behing them also,,,,this is the same principle really.

the building world is a fast moving enviroment and wedi boards and backer boards have been introduced because they are the best solutions available today.

just make sure that if the tiling fails, then the customer is aware that you cannot give a 100perc gtee because of the mdf that the builder installed, cover you backside and hold him responsible...good on top of bad doesnt necessarily = good??

 

[protilers]

Lee..as you say adhesive manufactures will not guarantee there adhesives on MDF in wet area's...but that is if tiling onto MDF...If kerdi was used onto MDf then no moisture can penetrate it..thus no problem with delamination or swelling.....that's what tanking membranes are for....I know what you are saying about tiling onto MDf and yes you are right....but using a tanking membrane or similar will do the job no probs......and so will ripping the whole lot off and using backerboards....

what about the moisture in the adhesive dave (in the two hours, if rapid,12 hours if normal set adhesive ),as mdf is (kinda) laminated........what if the first 1mm/2mm of mdf blow (expand) from the moisture in the adhesive......the tiles are gonna hold up for a while.......but i would not want to do a tap test (knock,knock!).......
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