For reference Bs8204:7:2003 and the gyvlon information pack says joints across door thresholds and between independent heating zones and where heated meets unheated and wher aspect rail is greater than 6:1 for heated screeds.......
At the end of the day we all try to do what works and if you bridge joints with ith and rubber crumb and it works the fine. But of course we all know that all he accepted Stndards and practice guides say do not bridge substrate joints
All of the screeders who come on my course are told unequivocally about the need for joints as are the tilers that come on my course....
i wish all the screeders who did anhydrite on floors i tile had gone on one of your courses.
i actually started my post with far too litlte info as we all do at times and hope i havent given timelee wrong advice . from bs perspective you and phil and perfectly correct and i know what should be done or not , by the book so to speak,but in reality i have put expansion joints in floors probably only a dozen times in around 1200 floors laid. this is only because they are domestic houses and clients dont want them.
the failure rate at a guess has been less than 1%.
i always say they should have them but if they are adamant they dont want to see through pattern i need to give an alternative and point out the risks and also say i am not responsible if there is a problem later.
this is not being iresponsible in my view, it is giving a client a choice with their floor.
it is always put in writing and there is never any argument even when i do with big contractors.
in timelee case , he says he has underfloor heating. i am assuming that heating is in screed and in trays under chipboard or could be screed between joists. As bugs and phil say chipboard is not good to tile on and i would always tell someone i recommend to lay ditra on good quality load bearing , absolutely rigid ply not chipboard.
also recommend that joists have noggins fixed near join to help this.
but this throws up another problem that no one has mentioned yet. even though you may go for an expansion joint and i do suggest this always if the tiles are laid in courses and can set floor out without compromising normal tile set out , as joint will become part of floorlayout, schluter now say that they do not guarantee their mat on plywood screwed in to joist over water fed underfloorheating. this is a change in their stance from a couple of years ago.Again in many instances this part has already been done , and i can only repeat what schluter says and make a disclaimer but i am not going to give away the job because of this.
it is not about being unprofessional ,it is about giving my client the correct info and a freedom of choice for them. In reality i have tiled over countless bath floors that have water fed heating under plywood and never had a problem but i wont guarantee work, now schluter changed their spec.
but i think that in many instances if i just walked away and client got someone else in they may very well be putting my client at more risk than i would have done.
of course there are other instances where i really see a problem with high risk of failure ,like the post i put up few weeks back where water heat pipes laid on top of screed !!!
i could not see a method that i thought would have a very low risk of failure without adding new screed over which height did not allow. i said no, stoneage said no and client has now got someone else to do it who say they are recommended by artisans of devizes. if they are they should know better and this will be a disaster. a very good job lost but not taken for good reason.
back to expansion in doorway, i do alot of quite large floor areas where stone will follow through maybe four or five doorways. another option i give builder again with no guarantee is that we cut a safe distance down say 25mm in to screed with grinder to create a weak spot which will enecourage screed to crack at that point hopefully. i then suggest i make one piece stone thresholds through doorways the thickness of the frame and fix these up to frame in rubber on top of ditra again . this breaks pattern but is uniform through all doorways and looks quite smart.if problem occurs can dig up the threshold piece and replace without having to get tile up that might have been cut around frame and now sitting under achitrave and skirting.
