I went to measure a cottage with a stone flag floor ( approx. 50 mtrs ) to be fitted with Karndean herringbone. The customer is having the flag floor taken up , a new concrete / cement floor ( with DPM and damp proof course etc ) with underfloor heating installed (hot water pipe ). My questions are these , 1 This will probably need a surface coated DPM, unless thoroughly dry obviously, will I be able to screed under /over the DPM with underfloor heating ? 2 Would it be better to use Karndean Heatpack , or similar ? 3 If the heatpack was to be used , would the DPM still need to be used ? Obviously , there is a cost issue here , so if I can get rid of the need to DPM and screed, instead using the heatpack it might work out cheaper . Any advice would be good thanks Phil
I think you need to let it dry out mate, the dpms are a bit suspect over ufh, if the subfloor cracks your shagged. I thought heat pack was for electric ufh but you could probably still use it over water Im guessing? Still you wouldnt want to put that stuff over a screed thats drying out!
So am I right in saying, no DPM , let the floor dry naturally and thoroughly, then use Karndean Heat Pack. Is that correct ? Phil
I assume when you mention heat pack you mean the versa lay? If the sub floor has a dpm laid prior to the new concrete floor being installed then water ufh in a concrete screed all you have to do is allow it to dry naturally. I take it the customer is getting a builder to do the afore mentioned stages? If so, you're part should only start now with an initial primer coat onto the new sub floor followed by a 3mm self smoothing screed and fit the Karndean direct on to the screed. I tend to apply a second primer coat onto the screed prior to fitting for extra piece of mind. This way avoids using the versa pack which I find expensive and not as good a finish as full stick down. One to watch out for.... the builder may not give the same attention to detail when smoothing the uhf screed. If this is the case I would recommend a filler coat of self smoothing into any imperfections then a second 3mm coat for a good finish.
Heat pak is made by jumpax, personally I think it's a really good product and it will give you a perfect subfloor to lay lvt on. Like I say not sure if you can use it with water ufh as I've only fitted it over electric mat
Now come on !! Even Karndean isn't made by Karndean !! Allegedlly ha ha !! So the plan is , to let it dry thoroughly, then it can be screeded and fitted. No need for the Heat Pak at all so long as the floor is dry Is this right ? Phil
