Wedi over chipboard?

[trevortine]

So I'm pricing up a job just now and the architect has specd up 2500x600x10mm wedi board over chipboard, electric heating over that and then tiled. Apart from the fact he has missed out slc over cables I cannot see this being viable. The addy choice between chipboard and wedi was Mapei ultra flex, an s2 adhesive albeit but when I mention mechanical fixings on top, ie wedi washers and screws they say no need? There's 50m2 of this to do and I need it to be 100%. I recommended fitting hardie to chipboard first and then insulation but there is height issues, as well as the extra cost. Have priced up both options and there is a considerable difference, any thoughts, would you do this?

 

[trevortine]

No takers on this one!!

 

[Rookery]

If it were my job I'd fix the Wedi to the chipboard with Weber RSF and Wedi screws & washers. I'd flood the cable with Weber Floorflex then tile with Weber RSF. If the tiles are stone I'd probably add Dural uncoupling membrane too.

 

[trevortine]

Just not so keen going direct to chipboard with insulation boards.

 

[Rookery]

I dont see much difference between sticking down a cement board and sticking down a cement-faced board.

 

[trevortine]

Cement board takes about 40 screws, wedi 2500 x 600 about 18 as they recommend.

 

[Rookery]

You can put more Wedi screws/washers in if you feel it necessary.

 

[trevortine]

You can put more Wedi screws/washers in if you feel it necessary.

They are a bloomin fortune though!! There's 50m2 to cover!!

 

[Rookery]

Presumably you'd cost it into the job? In any case, Weber RSF is likely to be a lot cheaper than Mapei Ultraflex so swings and roundabouts.

 

[trevortine]

Yeah defo will be costing in but materials reaching a fortune so far!