If I put down a new screed and Dpm over a very wet subfloor will it effect the drying time of the new screed? Will it always eventually reach 75% rh?
if the subfloor has a working dpm under it then applying a surface dpm will slow down how much residual building moister escapes. It will basically lower the RH of the moister escaping from the subfloor . It will be a lot lower than 75%rh. Maybe equal to 30% rh will be coming through the surface dpm ? Yes the subfloor will still 'dry'. But lets say it needs 6 months to 'dry' below 75%rh then applying a surface dpm will make the floor need maybe 10 years to 'dry' to below 75%rh. This is actually a good thing. The slower it dries the stronger it will normally become. Bit like a power floated subfloor takes many many years to dry but is still sand and cement and dries way harder than a none power floated concrete floor.
What I mean is I've got a new 75mm screed that's been down around 2 and a half months and still reading 89%. I wanted to wait until it reached 75% then put down 1k turbo before sticking down 260mm wide solid oak. Im now thinking will I be waiting for ages for it to hit 75% and do I just Dpm now. This has been a problem subfloor so it's a rather be safe than sorry.
for ANY bonded woodfloor the RH needs to be below 65%RH. This is almost impossible to get as the moister above the subfloor will also play a role in teh subfloor moister. Take how wet it has been so far this year but still warm enough to have no heating on. I would guess the AIR RH in your house right now is around 80% . What that means is if the RH of the moister above the subfloor is 80% RH then that subfloor cant 'dry' below 80% RH until the moister above it lowers. Come winter time the heating will go on and dry the air above the subfloor, this will mean the subfloor can now carry on drying to equal to above it. When it does get to say 75% rh you can install a vinyl product. The vinyl product will now protect the subfloor from moister above and teh floor will stay at 75% and below. However a wooden floor will allow the subfloor to take on moister again. This is why you should ALWAYS apply a surface dpm when fitting a bonded wood floor. What you effectively end up doing is protecting the wood from what the subfloor is doing and the wood will react to the rooms Air RH, not the subfloors RH. That make sence? PS, i know you understand the above RH but i try and make my posts understandable to others.
Yeah that does make sense, the air rh was 55 this evening but I haven't checked it thru the day so that could of slowed it down
you mean to dry to below 75%. Also it will be around 3-4 months. Concrete normally needs around 6 weeks drying before a surface dpm can be applied.
That sounds more like it! Im gonna get rid of this testo, either im reading it wrong and getting the rh mixed up with the temp or its busted. I will give it a few more weeks, dpm it and get a decent moisture reader
have a look here - http://www.weatheronline.co.uk/weat...F&ZEITRAUM=04&MONAT=12&JAHR=2005&ZUGRIFF=____ this is what the humidity has been over last few days. If no heating on or dehumidifiers then the RH inside a property cant be lower. It will most likley be higher as drying clothes, showers, cooking etc. Should also give you a idea on how teh concrete floor cant possibly dry any faster if the moister above it is high.
That's what i meant although the you pass 50 mm depth the time for drying doubles, 4-6 months on a 50 mm slab.
Standard unmodified screeds will typically dry at the rate of 1 day per mm, so for a 75mm screed that's 75 days. That can be speeded up by modifiying the screed with, for example: http://www.screeds.ronacrete.co.uk/...rlay-for-unbonded-and-floating-screeds.25968/ Drying time for 50mm, 8 days, to reach RH < 75% at the surface. RonaScreed 8 Day Overlay screeds at 50mm reach RH < 80% after 3 days and 75% after 8 days and a 28 day compressive strength in excess of 40N/mm² Can be used with one of our DPMs too.
