I have a 35sq m lounge Half the room has the original wooden floorboards which have been lifted,with insulation suspended between the joists and the relaid,then lined with 6mm ply ready to accept the final choice of flooring. (hakwoods engineered duo plank 20mm/180 wide. The remainder of the room was the original quarry tiled floor which has been lifted. The floor was dug down to a depth if approx 10 inches with a hardcore base,sand viscuine,insulation etc,new concrete slab approx 4 inches,and a finishing screed of approx 2 inches. This was done the first week of November. I have had 2 fitters come round to quote. One seemed to a little too keen to get the job done although to be fair I have seen 2 examples of his work and it is to a good standard. damp meter read between 10% by the front door(more air flow) and 17% ?? this was 1 month ago. This was done using a two pronged damp meter. ??it look more suited to walls/wood than concrete ? The other fitter who is a proper master craftsman and the wood supplier, don't recommend a liquid DPM as they say they are more suited to an existing old concrete floor with out a viscuine DPM (they seem a little more old school)and insist the moisture has got to go somewhere. They say I should wait around 6 months. I am wanting to get the floor fitted in early March so 4 months after the subfloor was laid. As this is an big investment I want to make the right choice and don't want the floor to fail,but time is an issue. Given the quality of the Hakwood product should I wait the extra 2 months till the moisture level comes down to 4%(no guarantees this will happen in time) Are these Liquid DPM products (f balls etc long term proven ) What are your experiences as floor fitters?
After about 4 weeks new slabs can have a liquid Dpm applied. The slab will still dry just takes longer which also makes it stronger ! I'd use ardex 1c Dpm on a new slab as it can suppress moisture up to 98% RH as long as moisture readings arnt above this. The % you've given aren't RH % far to low ?
Some things for you to consider. 1- A pin meter is for reading wood moisture (WME) 2- There is no official scale that will give a reading off 17% or what ever reading it was on concrete, Unless it was reading in a wood scale. Obviously they was not reading wood! 3- British Standards is Below 75% RH for floating wood or below 65% RH For bonded wood. (read on a hygrometer with a scale of 0-100%) 4 - If in Europe a MC moisture test might of been taken. This reads from 0-6.9%. You should be looking for around 2.5%or 3.0% depending on what method of install will be used when dry. But please note that this is not a British Standard test. 5- Surface DPM's are tried and trusted. Been around many years. 6- Surface Dpms are for use to hold back residual building moisture (so new concrete) 7- Surface DPM's should not be used on damp concrete (old concrete subfloors) . However there are now a couple that the manufacturer is saying you can use on damp concrete also. Very new to market and NO they are not proven. Far from it on the amount of failed ones we are seeing. 8- A surface dpm is recommended on ALL wood installs if the flooring is to be bonded, no matter if the concrete is considered as dry or not. 9- pictures can always look pretty, doesnt mean the floor will last. The above is the basics a Quality wood installer should know !
I think you should leave the floor to dry out as long as you possibly can then use a liquid Dpm. Bit worrying if your wood fitters are not testing for moisture with hygrometers or something that gives the correct rh reading! Like you say its a lot of money so If it was me I would take every precaution to stop moisture getting into it.
as matt says 2 pin is not for concrete testing must us hygrometer to rh %, i always liquid dpm when fitting wood as even if its the subfloor is dry enough now you never know what happens down the line and why risk it.
