Moisture ingress in below ground living area

[klauster]

Was that an above ground water issue?

Just 2 examples:
[1] Flat section - moisture entered above the moisture barrier and traveled inside the house. After digging a trench exposing and ventilating the concrete slab (wind & sun) and draining the trench – problem resolved.

[2] Two storey house, lower level facing the hill, suffering dampness - solution: timer controlled fans remove the moisture between retaining and the back wall of the house, plus floor heating keeps the basement concrete slab dry.

[Merlot Mike]

[2] Two storey house, lower level facing the hill, suffering dampness - solution: timer controlled fans remove the moisture between retaining and the back wall of the house, plus floor heating keeps the basement concrete slab dry.

Was that a below-ground concrete block retaining wall that was part of the lower level? If so it sounds like my situation. Did you consider excavating behind that wall and laying a new french drain (I think they're called) plus waterproofing wall?

[klauster]

Yes concrete blocks
Upper storey had adjacent to the house a concrete footpath with backdoor, no machinery access, nor option to excavate, opened from the inside, only limitations, so drained the hill side and ventilation has finally worked.

[John the builder]

MM

it's way in to the blockwork will rust the rebar and cause spalling of concrete in years to come.

so do you paint your driveway for the same reason?

You can assume the rebar is protected by concrete cover. The leaks in blocks (between cores filled with concrete) and joint at floor are usually the issue.

This is repairs and maintenance and under schedule 1 doesn't need a building consent. If no consent required then no council involvement.

[klauster]

MM

so do you paint your driveway for the same reason?

Thanks John, Very good point

[Merlot Mike]

Yes concrete blocks
Upper storey had adjacent to the house a concrete footpath with backdoor, no machinery access, nor option to excavate, opened from the inside, only limitations, so drained the hill side and ventilation has finally worked.

Any waterproofing applied to the interior of block wall?

[Merlot Mike]

MM


so do you paint your driveway for the same reason?

You can assume the rebar is protected by concrete cover. The leaks in blocks (between cores filled with concrete) and joint at floor are usually the issue.

This is repairs and maintenance and under schedule 1 doesn't need a building consent. If no consent required then no council involvement.

That's an interesting point... concrete blocks are of course very porous but is the poured concrete in the rebar cores non-porous?

[John the builder]

is the poured concrete in the rebar cores non-porous

it should be

if you remove the gib the pattern on moisture ingress will likely mimic the block joints

[Merlot Mike]

Something else that occurred to me: there's a fairly large established tree planted right up against the exterior of the wall... I wonder if the roots have caused damage to the block or mortar over the years.

[mrsaneperson]

Similar problem here with internal water leaking between cracks of the block to concrete foundation. The contractor used Ardex Hydrapoxy WPM 300 for the internal Waterproofing and gave a 15 year warranty. There are a lot of products on the market but the Ardex one which comes from Australia seems to be one of the best.
It is very expensive around $500 for a 10Litre pale.

[Merlot Mike]

Similar problem here with internal water leaking between cracks of the block to concrete foundation. The contractor used Ardex Hydrapoxy WPM 300 for the internal Waterproofing and gave a 15 year warranty. There are a lot of products on the market but the Ardex one which comes from Australia seems to be one of the best.
It is very expensive around $500 for a 10Litre pale.

Was external excavation an option?

[mrsaneperson]

It was a very difficult access area which would have required a lot of shifting dirt , tight space to work in.
So far so good, its being around a year now but if we still have problems in the future I guess excavation would be the next one.

With the internal sealing option, at the same time we replaced the carpets in both basement areas that were affected and replaced them with tiles. So if their is some moisture ingress in the future via storm flooding it is fairly simple remedy to clean up rather than carpets which get damaged.

[klauster]

Any waterproofing applied to the interior of block wall?

It was 15 years ago, no recollection what products I used, and sold the house after owning it for 20 years.

[Merlot Mike]

I suggest you check the cause of water entry before engaging someone with a vested interest is selling you their system. Our experience is that internal applied waterproofing is problematic in that it generally a) it does not stop water from entering the wall, only reduces the amount flowing out from it. You still end up with a cold wall because of the moisture in it and moisture in the air will settle on the cold surface ( dewpoint problem). b) some of the applications such as crystalline grouts require repeat application and while thye can reduce ( but often not eliminate ) moisture, if the wall has a crack subsequent movement can allow the backed up water to enter again. It is more than likely that because your gib is soft there will be a good fungal growth on the reverse face and often the dominant type is stachtbotrys . Be careful with handling that - MBIE has guidleines
Nutshell - identify real cause- there are NDT moisture meters that track moisture intensity paths in block, concrete and the like
Regards
Paul P

So external waterproofing really is the only satisfactory solution by the sounds of it. Do you have some professional experience with this kind of thing?

[Incodo]

Reasonable amount- commercial building consult type
Few points
1 If it's a large deciduous tree nearby, apart from roots growing longer and wider and lifting your founds like concrete paths, they also can affect ground water levels as they're thirsty during spring growing branches and leaves. Might need to remove it as it can crack walls and floors
2 If the building is say 20 years old or more, bitumen based materials such as Mulseal were common. These don't bridge new cracks well and application was more often than not poor. If the Mulseal was applied above ground level, it doesn't take the sun well over long periods and weathers away. Simiarly using a weed eater against a wall can cut through the protection
3 We also find that if a low level field drain was placed before backfilling, it may not have had a filter sock around it and could be blocked with sediment or plant roots or both. Blocked rains raise the water table. A plumber with a borescope can check this
4 Personal preference is using one of the peel and stick membranes such as Bituthene from the exterior as a) it's sort of self sealing and b) it's elastic so can bridge cracks
5 There was also a comment re block walls are waterproof in themselves. Short answer they're not - they have weak points where the blocks join together ( mostly an air space) and blocks soak up water readily.)Try a dry one in a bucket of water for 10 minutes, take it out and the tide level drops. Plus they're usually filled with a wet mix that shrinks as it dries leaving a gap between the filled cells and the block holes
6 I'd suggest an NDT meter is used to track the water entry point from the inside as the results could save a lot of unnecessary work e.g if the leak is at ground level becauee of weathering its a simple patch, if its a blocked drain it may be able to be cleaned and nothing required to the waterproofing, but if its linked to cracking - sorry Houston new membrane may be required
Regards
Incodo 0272800036