small damp patch. is dpm necessary? + walking on f-ball 700

[rangorgubbins]

Hi,
Just want to check I'm doing this right.
I want to lay vinyl tiles in my kitchen. The floor at the moment is mainly wooden floor boards, but with about 1/3 concrete. Both are very old and look/feel dry, apart from one corner of the concrete which has a damp patch. The damp patch is possibly caused by the exhaust from the combi boiler having been turned around while scaffolding is up outside. So the steam is blasting onto my exterior wall, running down it and coming through to the inside. I'm hoping that once the scaffolding is gone (next week), and i can turn the exhaust back round so it faces away from my wall the damp patch will dissappear.

I'm planning on:
Level the floor using 6mm wpb ply over the floor boards.
Raise the height of the concrete side to match the ply side using latex
smooth and level between the two floor types using f-ball 700 flex
glue and lay my vinyl tiles (karndean)

Queestion is: do i need to hire a hygrometer (HSS) and properly test my RH%? and apply a dpm if its above 75%?
Or will all the latex and f-ball goo protect my vinyl tiles?
The patch in the corner i mentioned will be under the kitchen units, so won't be tiled.

Also, if i decided to go for ceramic tiles rather than vinyl, the above prep be suitable?

One more question! Will the f-ball 700 cope with being walked on? If so, how long after its gone down is it safe to walk on? The chippy is coming on saturday to fit the kitchen!

Sorry for huge post and lots of questions.
Cheers for any help.

 

[flooringman]

You will certainly need to check for moisture on any sub floor you are going to install Karndean.

Providing your floorboards are sound 6mm. ply will be ok for Karndean but not for ceramic tiles. The 700 should go off in a few hours depending on conditions.

 

[mac391]

The only way to get a true humidity reading is by using a hygrometer and yes your RH should be below 75% so you don't have to install a DPM (damp proof membrane)
Block and beam shouldn't hold moisture the same as a concrete slab but do the test if you want to be safe. Bear in mind that if your RH is above 75% you need that liquid DPM, F-ball F75 or F76. The latex and goo will not surpress moisture !!

F-ball green bag and latex would be a sound and much cheaper option to 700 flex.

All above is sound for karndean but 12mm minimum ply required for ceramics which makes for a fairly hefty and pricey matching screed.

I would lay the screed and ply after the kitchen is fitted but tell your fitter to allow enough space under the worktop for additional floor height... if you do want to lay it before kitchen fitter, most F-ball products can be walked on within in a few hours, check their website all the info is on there.

 

[rangorgubbins]

cheers flooringman and Mac.

I have tested the humidity with hygrometer, and it read below 10% everywhere except the wet patch which was around 50%. I've found the source of the wet patch now (very small leak on boiler), so that shouldn't be a problem anymore.

I've decided to go for ceramic tiles, so will lay 12mm ply.
I've already primed (p131) the concrete ready for a dpm tomorrow morning. Before reading your post Mac, i was intending to apply the dpm (f76) over the concrete, then lay 12mm ply over the whole floor - both floor boards and concrete. Would you recommend doing this? Seems a whole lot easier than just plying the floor boards, then using screed to lift the height of the concrete by 12mm.

I also have some acrylic levelling compound. If i mix this with sand, could i use it to lift the concrete by around 8-9mm, then finish off with pure levelling compound to match the height of the ply.
Then tile over this?

p.s. the kitchen is only 10m2

 

[rangorgubbins]

I would lay the screed and ply after the kitchen is fitted but tell your fitter to allow enough space under the worktop for additional floor height... if you do want to lay it before kitchen fitter, most F-ball products can be walked on within in a few hours, check their website all the info is on there.

would you still recommend doing this if i lay ceramic tiles? Wouldn't the different floor heights be a pain for getting electrical in and out under the worktop, and moving the cooker (freestanding range).

 

[mac391]

You sounded like you were in a bit of a rush as the kitchen fitter was coming sarurday. Normally i would prep the whole floor while the room is empty, it's much easier. But... Yes you can install the kitchen first, then prep and tile the floor,, you just have to allow for 12mm ply, 3mm adhesive and 10/12mm tiles (total 25/28mm) when installing the units & worktop. The feet on your units should adjust to + and - 40/50mm so theres plenty of scope and of course you would tile into any spaces for free standing appliances, fridge, cooker etc. So if your tallest appliance was a fridge for instance at 860mm (height) you would add the 28mm to that plus a bit more to allow for your new floor. The kitchen fitter would allow for this so you can comfotably get appliances in and out, underneath the worktop. Go off the tallest appliance measurement to be sure all the rest fit.

On the screed side, i'm not sure if you can mix sand with acrylic screed. If you do, i'm sure it would have to be washed coarse sand. You can however, add aggregate in the form of granite chips to your screed, it's easy, and only about £6 a bag, F-ball will give all the stockists of it.This will allow for a screed of 10mm in 1 go, then an ordinary 2/3mm screed to finish.

If your hygrometer readings are only 10% i would fix 12mm ply all round and do away with the DPM. Fix the ply with a hilti nailer to concrete or adhesive or both!! and fix to timber with screws at 150/200mm centres countersunk.

 

[mattysupra]

hold fire!

There is no way you have hygrometer readings of 10% that is impossible!

How exactly have you taken the rh of the subfloor?

Also you cant dpm (f75/76) over 131 primer. The primer needs to be removed or a way around it would be to go over it with DPM base screed (acrlic ) and then apply epoxy.


Your readings of 10% need to be sorted first as these readings are VERY wrong.

 

[rangorgubbins]

The readings might not have been quite 10%, but they were very low. The scale on the meter wasn't uniform so I might not have read it accurately. However, they were definitely well below 75%. I measured it using a 'damp meter' from HSS. I just went over the concrete sticking the metal prongs in and checking to see if the meter showed green, orange, or red lights (RH over 75% showed red). The concrete was green lights all over apart from the damp patch which i've now sorted.
I think you're right, in retrospect i probably didn't need the dpm. Too late now as its down.

I checked the f-ball website, and it suggests using p131 primer for f76 dpm on concrete.

Do you think its possible to glue ply straight to the dpm, or will i definitely need a levelling layer ontop (either stopgap 200 - acrylic, or green bag)?
Do you know what type of glue i should use?

 

[mac391]

A damp meter won't give you RH readings, you need a hygrometer for that and it's a 48 hour test. However, you have a DPM now so it doesn't matter.

Use F ball styccobond B93 which can be used to fix ply straight to F76 DPM, no screed required. but your floor needs to be realy level. i would use this and still use a hilti nailer,(Hss hire)
Expensive for a small area but you've done it all correctly so far, no point in skimping on the last part!!

 

[rangorgubbins]

Does seem like a lot of effort for such a small area!

Where the concrete meets the floor boards there is rise (on concrete side). If i lay a 1.5 m rule over the concrete and boards there is a gap of about 5 mm at the end of the rule.
As i have the acrylic levelling compound already i was intending to use that tonight to smooth things over.
I'll caulk the joins between the boards around the concrete tonight then pour the acrylic over. Even if its not completely level it should smooth it enough and the ply can take the rest of the undulation.

I was intending to use No more Nails (Ultra) to fix the ply to the acrylic.
Surely if i nail into the concrete I'm ruining the dpm?

cheers for all your help with this.

 

[mac391]

ok,,, screed over the DPM, don't forget to prime with neat P131 first or it won't adhere. Then fix your ply to that. Not sure about "no more nails" but now that you have covered the DPM with screed it might do it. I would still use B93.

You are right about puncturing a dpm, it becomes useless if you do but your moisture readings were only 10% and it's unlikely you needed the DPM.

 

[mattysupra]

first off the moister meter you used is not for testing concrete. It is a indicator you use ONLY to know where to set up a hygrometer.

2nd- 10%rh is impossible to get, The lowest you will ever get is about 50% as the concrete RH (relative humidity) can not be lower than the air moister above it.

3Rd- are you certain that FBALL say use 131 before the DPM? That is not correct. 131 is not moister stable and will break down, also its shear strength is not high enough for DPM. I think you may of get things back to front. The 131 should be used on top of the dpm to bond the smoothing compound to the top.

4th- Acrylic is not sutible to install over floorboards. You need Fball Flex (700 i think it is) to go over the floorboards. Also dont go direct to the floorboards, install plywood first.


5th- plywood is used to smooth floorboards, screed compounds are to be used over concrete. I would consider using smoothing compound on the concrete side and not plywood.


Im not sure if the mods will allow a link? but you might find this intresting as it shows pictures and instructions of a floor prep between concrete and wood subfloor. http://www.theflooringforum.com/viewtopic.php?f=32&t=368

 

[mac391]

I hate to make this a conflictng advice forum between myself and mattysupra. The trouble is with pro's like me and him is we go by the book yet the idea of this forum is to advise you DIYers on what is the best way to do something yourself, and when on about DPM's ,adhesives and screeds it gets realy techno!! I try to strike a happy medium between what is totally correct and what you will get away with.

With total respect matty, on this project i assumed rangorgubbins was laying a screed over the concrete and not the timber sub-floor (even though it was higher than the floorboards) to create a flat but not level sub-floor, which is fine by me. The DPM is already down, no going back there and yes the P131 should go on top of the DPM not underneath, this is one that i think he will get away with and so advised accordingly.
Yes f-ball 700 flex over floorboards or ply is correct but he has already bought 200 acrylic that he will use over the DPM not the floorboards..which is fine..
It's sometimes hard for a DIYer to explain the full picture so you have to read into it.. In the end we have just totally confused someone who simply asked for advice.. Chill man and read the forum twice.. before responding.

Rango, what you have done so far isn't technically correct but i believe you will get away with...

 

[rangorgubbins]

yep its been a steep learning curve in levelling floors this week. But if it was too easy it wouldn't be fun!

Cheers for both your inputs.
I will carry on and make the best of what i have.

 

[mattysupra]

I hate to make this a conflictng advice forum between myself and mattysupra. The trouble is with pro's like me and him is we go by the book yet the idea of this forum is to advise you DIYers on what is the best way to do something yourself, and when on about DPM's ,adhesives and screeds it gets realy techno!! I try to strike a happy medium between what is totally correct and what you will get away with.

With total respect matty, on this project i assumed rangorgubbins was laying a screed over the concrete and not the timber sub-floor (even though it was higher than the floorboards) to create a flat but not level sub-floor, which is fine by me. The DPM is already down, no going back there and yes the P131 should go on top of the DPM not underneath, this is one that i think he will get away with and so advised accordingly.
Yes f-ball 700 flex over floorboards or ply is correct but he has already bought 200 acrylic that he will use over the DPM not the floorboards..which is fine..
It's sometimes hard for a DIYer to explain the full picture so you have to read into it.. In the end we have just totally confused someone who simply asked for advice.. Chill man and read the forum twice.. before responding.

Rango, what you have done so far isn't technically correct but i believe you will get away with...

Um, well i have adviced the correct way. I dont think you should recommened using products that are not sutible/designed for the job in question.

Also as your a pro im supprissed you never picked up on the fact that the subfloor moister reading are impossible to get? also you advice to nail through the epoxy surface DPM that would render it useless but you say this o.k as the subfloor moister is 10%?

The person who started the thread was asking about drying times etc of 700 flex. they was already looking at using the correct products and you have told them to use other products that are not recommended?


Or maybe i have this all wrong?