Concrete Slab Edge Dampness

[Ian (WA)]

'Morning All,

Seeking input from persons experienced in concrete dampness solutions.

Received email from Prpty Mgr & Tenant re edge dampness present inside garage wall on two year old townhouse development of mine.

See photo: left hand side t/house has problem area (photo of dampness taken inside garage by tenant). All T/House perimeter is concrete - no pavers for access, so concrete cutting will be req'd. I believe two ther T/houses in group do not have this problem....yet

See HIA flyer on subject re causes & prevention.

Wondering if anyone has any commentary / experience re a viable solution (i.e. preference re adhesive type membrane seal or any other product out there I can use).

Please Note: There is no builders obligation under insurance to rectify - I've already spoken with Sth Austrailia HIA Office & Builder on this.

Appreciate any comments.

Cheers, Ian.

 

[Ian (WA)]

Sorry photo of dampness now attached.

 

[redwing]

Lime leeching through?

 

[Ian (WA)]

G'day Redwing,

I was hoping that is all it is, but tenant is with HIA and has provided this commentary after showing photos to others at HIA:


“These pictures indicate the start of Slab Edge Dampness caused by the paving & moisture around the perimeter of the building.
I have attached our information sheets that HIA has developed for our Builders.
I think you should forward this information to the Land Agent as it could also be happening in the main dwelling if the construction was not correct.”

Doen't mean they are correct, but knowing the difficulties I had with the concrete contractor at the time (concrete paths were all laid 12 months after slab poured), my fear is there was insufficient membrane placed against the slab when paths were laid???

I will have it assessed properly, but am still looking for input.

Cheers, Ian.

 

[Scott No Mates]

Slightly confused Ian, which room has the damage? If it is in the garage, then the builder is correct in saying there isn't an issue - garages are not habitable rooms and do not require a membrane under the slab - so you may get damp floors, mould etc in your garage areas.

If however this is the hallway backing onto the garage, then it is a different story.

 

[handyandy]

Sorry photo of dampness now attached.

Which side of the garage is this photo off. The side where the front door is, the opposite side (on outer wall of building) or at the back of the garage which has what behind it.

Cheers

 

[Ian (WA)]

G'day Scott,

Thanks for your input...appreciated!

The moisture runs down the length of the garage right hand side wall i.e. drivers side of car when parked in garage....so not the skirting board backing onto downstairs kitchen/family room. See floor plan attached.

Your comment re membrane under slab is an eye opener for me; I was of the belief the whole slab was meant to have a non permeable provision from external moisture.

I could go a number of ways with this:

1). Trust it is only moisture/lime leeching up through garage portion of slab only and do nothing.
2). Have it (and remainder of slab & slabs on two other t/houses) inspected and hopefully get a clear determination of issue.
2). Attempt a remedial sealing to 'reduce' potential for further moisture ingress from outside the garage wall/footpath, that is if indeed external moisture is finding its' way in, as opposed to natural leeching of moisture/lime.
4)??? Other suggestions.....

Cheers, Ian.

 

[Ian (WA)]

Thanks HA...sorry was replying to Scott when your note came through :>)

 

[robboat]

Two years old.....and only just noticed...?

Looks like a "new" problem as the salts are pretty clean - e.g. still developing crystals as the dissolved salts dry out.

If that is the wall between the garage and the outside (garden area?) then is there a chance a reticulation system has started leaking?
Or water from another source...?
How well drained is the outside area?
Has there been unusual rain or water on that side for any reason?

What has changed recently?
That may provide the answer......

Good luck.

 

[Ian (WA)]

Hi Robboat,

Yep, only just been discovered by new tenant - not noticed before this. Going by staining to concrete it could have come through under old tenancy, but the email note from new tenant was quite explicit in that the salting wasn't noticed previously by them (been in property 3 weeks).

Attached another photo of construction work on two townhouses (mirror image plans, so what you can see of garage concrete works to right hand side dwelling applies to both townhouses)....on zooming I picked up on the black membrane between the timber frame and slab, but couldn't identify any waterproofing product to the slab proper. Bearing in mind, 75mm thick concrete paths were laid against foundations some 12 months after this photo was taken.

No poly retic lines down this stained side of property. Only other recent change was Adelaide got smashed with rain & storm squalls two weeks ago.

Drainage around outside of t/houses is all concrete paths with 90mm stormwater drains feeding to below ground stormwater tanks/pump system......I have not been present to see how well water gets away during a deluge, so can't provide qualified info on this.

Will have Prpty Mgr inspect all three garages on next visit (take photos of all).

Appreciate your input R.

Cheers Ian.

 

[morty]

Hi Ian,

I am a registered builder in Victoria but have spent the last 3 yrs living and building my own projects in Adelaide.

I have seen this salt build-up/dampness on a number of newly built projects but only in SA. It usually occurs, as you mentioned on the edge of the slabs, in between the external pavers or concrete and the first course of the bricks.
It is fairly normal and seems to happen more frequently on the shady sides of the houses.
I have seen it in the garages also and this shouldn't happen but i think that it is the result of the fact that sarking (builders paper/wrap) is not required to be installed in SA. This paper is for the condensation that naturally occurs on the inside of the brick (within the cavity) to run down the paper and then out the weep holes in the brick and then outside.
Without this paper the condensation just runs down into the house. You never notice it in the main part of the house but as there are no floor coverings in the garage it can often run under the skirt into the garage, as per your photo.

I'm not exactly sure how to cure this but i would make sure that you insist on builder's wrap to be installed on any future builds as i believe it is a glaring ommision in the SA building regs.

The only thing i can think of to try and get around the problem is to make sure all the weep holes in the bricks are unobstructed and if you are able i would even look into removing a number of bricks along the bottom of the wall and installing some metal vents so that there can be some natural ventilation within the cavity.

Anyway mate, i wouldn't be too worried as i'm pretty sure this is a common occurance in new homes in Adelaide.

Hope this helps, or maybe i've prattled on too much.

Either way, good luck.

Regards

Morty

 

[Aaron Sice]

is the garage paved? some nutjobs paved these things and they dry air above sucks the moisture out from under the pavers and causes HUGE headaches because there's no sun to dry them out.

if so, pull up the pavers ONE IN FROM THE EGDE (not at the edge) and replace with the smallest gravel / rainbow stone / bitumen you can find.

if theres any pavers on the OUTSIDE of the garage you need to remove them ONE AWAY FROM THE WALL AS WELL and treat the same.

this pulls the water away from the brickwork and allows it to evaporate properly without doing so at the detriment of your adjoining wall.

try to avoid parking in the garage for a month or so or the pavers will shift and leave the door up a crack when you, or your tenants, are home. pain the butt..i know.

 

[Ian (WA)]

G'day Aaron & Morty,

Many thanks for replies.

Aaron there are no pavers anywhere, I had an italian moment and concreted the whole site

It's a blessing most days, but at moments like this I think concrete cutting is not what I need right now

Anyway, I can't fathom rainwater run off being a cause because when you look athe last photo you can see the 90 mm stormwater drains system risers which feed underground tanks/pumps. There is actually one about a metre away from the problematic garage wall, so I would assume there hasn't been any pooled or flooding water in this vicinity.......unless that riser is blocked or broken underground.

I tend to agree with your view Morty, as now that I think of it, I recall seeing this type of thing on other slabs around Adelaide over the years but didn't think anything of it. In fact I also recall some crystalising on two slabs in Karratha WA.....dry as buggery up there (except in cyclone season).

Further to your comments, that breezeway between the two t/houses is always shady/cold/most as it gets little or no sun to warm up/dry out the concrete seams between paths and slab.......so I am hoping we are just seeing some lime/salt migration occurring in that non sealed section of slab after 2 years since being poured.

I'll get photos of other t/houses asap, then have them all properly inspected and see what comes from that.....just for some peace of mind.

Thanks again gents!

Cheers, Ian.

 

[Mush]

Hi Ian,I assume the garage slab and the outer concrete path are at similar levels allowing water penetration through the brickwork bed joint. If so you need to form a channel in the outer concrete and install a surface water drain running the full length of the garage and discharging to a soakwell or alternatively cut a full length channel at around 150mm wide x 150mm deep and fill with rainbow shingle or similar to provide drainage.