damp proofing concrete floor

[aidan.f]

I  have  a garage  floor  with  bitumen DPc with a  thin concrete screed on top, after 30 Years it's getting a bit of damp. What  are  my  options?

1, Floor  paint
2, Self  levelling  screed

What  is will bond and last? any  recommendations for products - I  did read something on this board about screeds but a quick search gave no results

[rafletcher]

Neither of your options will work for long, the only real solution is to break it up, and lay a new floor over a new plastic membrane

[mrcharly-YHT]

wot he said, unfortunately.

[Blodwyn Pig]

you'll have to take off the loose thin top screed, then brush off all dirt and dust from old conc slab. Then apply 3 coats of 'Synthaproof' damp proof membrane, then re lay screed, with a waterproof additive for good measure. when you apply the screed, wash the floor immediately behind where youre working , with a cement slurry.  But if it's only a garage??? the weight of a car will break up the screed any way if its thin.

[aidan.f]

Appreciate  the advice

The  top screed is in good condition - Should it take 'Synthaproof'  DPC - Having had a browse of t'Internet there seem to be plenty of Epoxy ones to choose from

10-20  mm of additional floor would be no problem No car - just  bikes - This is  YACF

[mrcharly-YHT]

Applying DPC on top will not work - it will just bubble up and be damaged.

If garage is only for bikes, I'd suggest either putting up with a bit of damp, or putting down a DPC membrane (the cheap blue stuff and laying something on top. Concrete screed would do the job.

[aidan.f]

it's not a  garage now.  workshop and den, so I will be happy to spend some money on a decent job. Insulating the floor as a part of this is a possibility:- There is  100mm of  insulation in the  roof and 25mm in the one outside wall. Wish I had screeded the floor before building  in the work benches (but it wasn't damp then!)  thanks for the advice

[ferret]

well has it's only taking foot traffic and bikes I would have thought that 4" of concrete would be fine, if you don't mind the finished floor level being a bit higher than it is now, break up what you have, blind it off with some sharp sand (make sure theres no sharp bits sticking out) put your DPM over that and then the concrete, not sure about insulating the floor starts to get a bit expensive then, I would get hold of a nice bit of carpet or thick rubber mats or there is some stuff that you can paint/pour on, self leveling I think but don't know how it reacts with oil and the like

[artyfaharty]

Two options:
Take the whole lot up, plastic membrane, concrete, battens, insulation, boards..

Or a bit of a bodge but will work
Membrane over what's there...
Then floating floor comprised of batten insulation and board?

[fred the great]

I could not recommend any "so called" liquid water proofing membranes

But a good quality plastic sheeting or roofing felt with at least 12" laps covered with 4" concrete will do the job. I think you should firstly remove the the area of the old floor to try to identify why it is damp before proceeding further

[Woofage]

Although a right pfaff, I would consider taking up the whole floor. Two reasons:

1. You'll be able to fix the damp
2. You can insulate the floor at the same time. This will make a big difference to the comfort of the room. (I've just re-read the thread and I see you are already considering this )

Taking up the floor is just labour. Hire a breaker and a big skip and in a couple of days you can shift the lot (I did our porch/utility in an afternoon ready to lay a foundation strip to convert a single skin wall to cavity). Wear hearing protectors on top of EAR bungs and don't overdo the vibration exposure.

Use the Celotex website to calculate the thickness of insulation you need (it's based on floor area and perimeter). Make sure you/your builder puts in at least this much.

[rogerzilla]

I could not recommend any "so called" liquid water proofing membranes

But a good quality plastic sheeting or roofing felt with at least 12" laps covered with 4" concrete will do the job. I think you should firstly remove the the area of the old floor to try to identify why it is damp before proceeding further

That might cause a few issues with getting the car over the resultant step 

[fred the great]

Request joined up thinking.

There wouldn't be a step if I did it