Sorting an uneven concrete floor

[screwpainting]

That is all down to damp Paul, it is coming up through the floor, and through the walls by the look of it and there is no timber based solution for it.
Avoid floating floors like the plague, it's the most idiotic flooring system ever conceived of and is only as good as the care taken to lay it onto whatever subfloor surface it is covering. It will not work on top of a very uneven concrete finish without that surface being spotlessly clean and properly prepared and that is more work than screeding the bloody thing properly in the first place.
As an insulation technique, it is fine if there is no other alternative, but I personally, think, it's still a handy bodge for all involved who offer no personal guarantee to the poor sod that has to have it all ripped out four or five years later along with whatever has been installed on top of it because it has sunk, makes a noise, rocks and rolls, or gone rotten in some way.
Again, great if done perfectly, but... just don't trust anyone to do it mate.

If I had your problem, I would first check the thickness of the existing concrete and look for evidence of a membrane and then establish precisely what you 'definitely' have in the way of a DPC as opposed to guessing.

I bet that floor is made up of all sorts of crapery and would be dead easy to turn into hardcore for a proper job of concreting a new floor right up to spec, damp free, flat and as smooth as a babies.
Sorting out a lack of a DPC is cheap and easy if necessary, just a little care and application and simply has to be done anyway.
The cost is all in labour, care and some newly acquired, simple skills.

Just my two pennyworth :wink:

 

[SammyQ]

That is massive damp Paul. I agree with Screwpainting that you have to address the penetration problem before anything else. You mention outside ground level is 'high'? Remember, the damp course has to be 6"/150mm above ground level? I would start by digging away the soil banked against the walls to restore this. Second, do you have a visible DPC in your walls? Is it in good nick? If so, fine, proceed. If not, see later.
Is your floor emitting damp? Easy way to tell: tape a freezer bag to the floor, well sealed edges, leave for a day, if condensation underneath you have upwardly penetrating damp. If on top surface only, you've got a ventilation problem, floor's fine.
Faulty wall and floor damp problems CAN be sorted. injecting and tanking come to mind. But, and it's an ocean-going-liner-size of a 'but', you have to make the place dry before you can do owt else. Mould spores LOVE 'free' water to germinate.
From experience, I can also tell you that those manky chipboard pieces will have to be replaced. As a Biologist with 40 years experience, I have never found a totally foolproof way of removing and then preventing resurgence of mould in 'reconstituted wood' - probably as it has such a massive pore structure and the spores of mould seem to hide in them?
There is an outside possibility that this is the worst condensation problem I have ever seen...but I don't think so; there seems to be just SO much fluid there, you'd have to be sleeping in the garage or cooking in it to provide the amount of moisture visible in the photos. The only other thing I could think of would be an unvented tumble dryer and I can't see one in the pikkies.
Finally, drying this baby out will need the winds and temperature of spring and summer. I would halt any thought of flooring until the problems are sorted. DAMHIKT. Sorry to be such a Jeremiah, but cash in a three-kid family is precious, I know, because I had 'three under three' at one point, who went on to be three at Uni simultaneously...

Sam, older, wiser, but still optimistic.

Edit P.S. Had anudder look at that floor. It's a piece of p1$$. Personally, I would break it up and relay it with a 1000 guage membrane underneath and 8"/200mm up the walls, or, if cash/time is tight, I would lay down a good, meaty, pair of coats of summat like Synthaprufe* - anything thick, tarry and plastic-setting (pliable) would work. I've even seen a quick skim of dry concrete troweled on to smooth out rough and sharp edges, then several days later, a coating of roofing cement, quickly followed by a rolled-on DPM. Rough as a bear's ariss, but it worked. The rube that did this, laid his floor and insulation on top and it worked. Just say'in... more ways to kill a cat than chokin' it with cream....

*https://www.wickes.co.uk/Ikopro-Synthaprufe-Trade-Damp-Proofing-Liquid---5L/p/151384

 

[Woody2Shoes]

I think that quite a bit of the mould on vertical surfaces is from condensation - is warm (relatively moist, from a kitchen/utility/bathroom) air able to infiltrate from the house to the garage? A tumble-dryer (even a condensing one) in the wrong place would explain everything.

Part of the solution to the problem may simply be to create a vapour-tight 'airlock' between house and garage.

Also, airbricks are all well and good but do they give proper cross-ventilation, without 'dead spots'?

I think that you do need to investigate the cause of the dampness on the floor under the side door (it's not impossible that this is simply accumulated condensation running down the smooth-glossed inner face of the door) Cheers, W2S

 

[SammyQ]

I second what W2S ses. If there IS a humidity source venting into your garage space, Bingo!
Sam.

 

[LarryS.]

Thanks everyone for the input, it sounds like I've got a bigger job on my hands than I thought, but i want to do this right as it's intended to be turned into a proper workshop over the next few years.

I'll go out on the weekend and check DPC, but to answer some questions / points.

Water ingress - The garage at some point has had the original big doors replaced with a roller shutter, which is mounted on the inside of the opening. Problem is the ground outside was angled for the original doors, where the new doors are there's a slight slope INTO the garage, which means on a rainy day there will be a puddle about 2ft x 2ft and a slim covering of the floor - so is that enough to cause the damp issue ?

Outside ground - its not actually soil that's hugher than the inside floor, it's a concrete path that is laid alongside the garage that is about 6 inches above the floor level, no idea why they'd have done that - but is taking that out and digging down the only solution?

thanks again for the guidance / advice !

 

[SammyQ]

Paul, find your damp course on the inside of the garage. If your wall is one brick thick, the outside pathway HAS to be 6" below the dpc. If you have a double skin wall, in theory you could have an internal 'step' in the dpc, allowing for a higher outside path, but I greatly doubt it's a good idea. MikeG may want to correct and enlighten me, he's better at this than most here. Banked up material of any sort, bridging a dpc, equals damp rising up the walls and humidity diffusing from them causing havoc.
Secondly, that puddle is a complete non starter. THAT is - I earnestly suspect - is a major contributor to the humidity in your garage that the mouldies LOVE and flourish in. Great encourager of the tin worm too. It's got to go. Improved drainage or reversing the slope outside,( with a cast sill, upon which the door rests?) even a simple soakaway would magically help.
Keep asking fella; weve all been there and can guide your thinking. Save heartache and frustration by avoiding our ballsups. Experience "is a hard mistress in that she gives the lesson AFTER the sanction". Us old lags would rather that fewer noobies got pummelled by her.
Sam, been there, cocked up that.

 

[LarryS.]

Thanks Sammy, the inside is rendered so I guess I’ll need to hunt for a doc black line outside ?

The only damp I’ve noticed is the puddle plus that small amount around the door area, so maybe a puddle fix and door may solve most of the problem. I’m also going to do a hunt to see if there is more mould around the garage but have seen nothing obvious til now, so maybe there is a dead spot on the airflow

Casting a new cill sounds very doable; ideally I want to build garage doors back in their original position but having time for that is probably a few years away !


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[MikeG.]

.........Outside ground - its not actually soil that's hugher than the inside floor, it's a concrete path that is laid alongside the garage that is about 6 inches above the floor level, no idea why they'd have done that - but is taking that out and digging down the only solution? .......

It's not the only solution, but it's part of the only proper solution. This is the very first thing I get clients to do with any of their old buildings: lower the ground level around the perimeter until it is 6 inches lower than the finished floor level. Sometimes this isn't practical, but even getting it 2 inches below the floor level will be a huge improvement. It also shouldn't be a solid surface adjacent to the building, with shingle being the best thing to have against the wall. Lowering the ground level at the sides will force you to lower the ground level at the front, too, which will help reduce the water ingress at the door, (an absolute disaster at the moment). This advice all applies whether or not there is a DPC, (and not having a DPC isn't the huge deal that some will claim). I'd be looking at an Acco-type channel-with-grill drain in front of those doors, in addition to sorting out the levels, but such a drain only works if there is a suitable place to discharge to.

Of course, you can achieve the same ground level to floor level difference by raising the floor level, if this works with floor levels in adjacent rooms, head heights, adjacent DPCs, and so on. I am really reluctant to try to give you a personalised solution in your specific case because walking around the building is the only way really of finding out what is actually happening.

As a first course of emergency action, stand a dehumidifier in there, and empty it regularly. This is no long term solution, though, as you are essentially trying to dehumidify Dorchester......a losing battle. I can't stress enough that mould is dangerous. It has serious health implications, and once you get everything dry, you should be cleaning everything down with an anti-fungal solution, and disposing of any affected timber (such as that plywood).

 

[Woody2Shoes]

Thanks everyone for the input, it sounds like I've got a bigger job on my hands than I thought, but i want to do this right as it's intended to be turned into a proper workshop over the next few years.

I'll go out on the weekend and check DPC, but to answer some questions / points.

Water ingress - The garage at some point has had the original big doors replaced with a roller shutter, which is mounted on the inside of the opening. Problem is the ground outside was angled for the original doors, where the new doors are there's a slight slope INTO the garage, which means on a rainy day there will be a puddle about 2ft x 2ft and a slim covering of the floor - so is that enough to cause the damp issue ?

Outside ground - its not actually soil that's hugher than the inside floor, it's a concrete path that is laid alongside the garage that is about 6 inches above the floor level, no idea why they'd have done that - but is taking that out and digging down the only solution?

thanks again for the guidance / advice !

Yikes!! - puddles are a definite problem, so are outside ground levels - as Mike says.

Is there an opening into the house from the garage? Are there any machines like tumble dryers?

Cheers, W2S

 

[SammyQ]

That's the definitive answer Paul. MikeG is THE source on this forum for building issues. I fully concurr with him re medical issues from mould spores; I had not wanted to increase your groan factor by raising it, but hinted above that the wood needed replaced? Basically, think asthma, bronchitis, Farmers Lung as a starting point!
Good luck, and please come back as often as you feel the need. PM's are also welcome if you feel you don't need to ' broadcast'to the whole forum. Just don't ask for lottery numbers... 8)
Sam

 

[LarryS.]

Apologies this is photo heavy, but a bit of an attempt to show the layout / surrounding area, so I've taken some photos.

The setting of the garage, basically at the top of the slope of our driveway:

At the door you can see the roller shutter, that comes down BEHIND the opening, where the original doors would have been, and the slope away starts, so the movement of the shutter to the inside causes rain water to seep under. You can see the dark conctrete where the water goes under, behind the door

The DPC it turns out is only one brick above ground level right at the front

And at the left hand side the path starts 1 brick below DPC

but by halfway up the garage is only 1 inch below it

by the time we get to the back, the DPC is crossed, and the ground is higher again, plus there is a wacking great big oil tank there with its pipe concreted in

Down the other side of the garage looking from the front again the DPC is crossed again, with the ground, and unfortunately next door are growing a eucalyptus (or something like that) which I am constantly battling to keep down - but it is riddled down that side

So in short dropping thr ground all the way around looks like a fairly huge task....is there an alternative ? I understand a bit about "tanking" could that be an option, plus raising the DPC up and tanking to that point ?

 

[MikeG.]

OK, well there is some good news in all that. With the garage sitting on the top of a sloped driveway, sorting out the issue at the roller shutter door threshold should be fairly straightforward, and in particular, there is an RWP (downpipe) adjacent.

I would start by digging away at the front of the garage to reduce the ground level of the drive at the threshold, but still have that drive sloping away from the building (ideally by about 1 in 40). I would also dig a shallow trench in front of the garage door, and install in it a gulley with grill,like this. Check that whatever you buy is suitable for whatever traffic it is likely to have to cope with. Some of these channels come with a built-in slope, and others you have to lay to a slight fall. Whatever system you install should shed its water towards the downpipe on the right hand side of the door as you stand on the drive looking at the garage. You'll obviously need to dig away around the downpipe to expose the drain and make a connection to your new gulley. This should entirely resolve the issue of water ingress at the garage door threshold.

I presume that the door adjacent to the oil tank is the door showing the damp issues in your earlier photos. Firstly, I'd be closely examining the nearby downpipe to see if that is leaking. If the junction with the gutter isn't perfect, water will often run down the outside of the pipe, and can be pretty difficult to spot. That little return in the wall by the tank (or is it the end of the garage?) doesn't help either, because that is an obvious moisture trap. Can you check to see that the paving there falls away from the building, such that rain has a chance to run away down the path........or does rain get trapped against that wall in the corner?

Personally, I'd prioritise the front door and the gutters/ downpipes etc, and do the plastic-on-the-floor trick to see if groundwater is getting through your concrete in the middle of the garage..........and that's pretty much all I'd do this winter other than clearing any detritus from the narrow area alongside the boundary fence. I'd install a dehumidifier as I suggested earlier, and just monitor damp levels in there into the spring and early summer. I absolutely would not do any tanking internally until things were much drier than now, and we'd need the results of the plastic-on-the-floor test before assessing whether digging the floor out and installing a new one is worthwhile. It probably is, but this will also involve raising the side door threshold and thus getting a new door, so let's not rush at that.

I can see value in breaking out the concrete footpath and laying a new path at lower level. That would probably entail a step, or a short ramp, at the corner by the oil tank, so you'd need to assess the practicalities of that. The new path should be away from the garage wall, six inches if practical, and the gap filled by shingle.

 

[beech1948]

MikeG is right in his approach to what you should aim for this winter.

I would add that the narrow RHS strip between you and the neighbour has what looks like an invasive bamboo ( not eucalyptus). This will also add to your problems as bamboo is able over time to breakthrough 3-4 inches of concrete. An approach here is to dig it out (ouch) and to put down a layer of herbicide and salt or something which will persist and maybe spread to kill the offending bamboo next door. Maybe talk to the neighbour about it as digging it up is hard work.

A busy winter ahead it looks like

 

[screwpainting]

Looking at those pictures Paul, I think it looks as if all the surrounding ground and particularly the actual path on the left hand side, actually fall towards the garage. This could easily inundate and overwhelm that dpc in heavy rain and I think it might be a good idea to check this with say a dustbin full of water tipped over by that oil tank (proper scientific)and just see where it actually goes.

What you could do is make a hole in the roof, then you would have the full set of possible water ingress points, looks like you have all the others there mate .

MikeG has pretty well summed it up.

 

[MikeG.]

I'd just nuance what screwpainting has said by saying that the DPC is only important for protecting the brickwork above the DPC, but not for preventing water getting into the garage below it. This is why I said earlier not to be too fixated on the DPC, because even a properly placed DPC, 2 courses up from where it is now, would make not a jot of difference to how much water is getting into your garage.

I get to deal with ancient buildings a lot, and with older-but-not-ancient ones too, and they invariably have no DPC at all. Damp can be well managed in those by paying close attention to the fundamentals, as we're doing here with this garage, and the DPC or lack of is an irrelevance. This doesn't take away from what screwpainting has said about getting the falls away from the garage walls.........another good argument for removing that side path (if it is falling towards the garage).

 

[SammyQ]

Yup. Dat am bamboo Massa Paul. Flamethrower and JCB Suh....odderwise you'se'a gonna be overwhelmed.
Sam(bo) ...with deep apologies to Samuel Langhorne Clemens...
Edit: Wrong! Not Clemens, Gerald Durrell.

 

[LarryS.]

Thanks Mike / Sam, I’ve put down the plastic plus a paint tin so I’ll see in the morning if the floor is shot

As for the works needed I may have the time to do the garage front but the rest of it is probably months away (3 small kids) so I may have to put up with the damp for a while yet. Good point on the down pipe though I’ll check that tomorrow as it’s been blocked before.




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[MikeG.]

........ I’ll see in the morning if the floor is shot........

Leave it 24 hours.

 

[SammyQ]

Yup. More if you can; over this weekend maybe? Dunno if there has been much precipitation where you are, but it's been dryer and frozen here, which tends to limit water ingress, so clagging up the polythene could be slow.
Sam

 

[LarryS.]

Rained most of yesterday and this is the result, so very slight darkening

I’m guessing that means bad news ?

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