Should I install air vent?

[amir47]

Hi Guys,

First time in my life that I went into the crawl space, I found a separate compartment which underneath the front door stairs.

To my surprise, I didn't see any air vent for that compartment. There are also lots of buildup on top of the compartment.

Is this normal? or should I install a few air vents there?

[Adam_W]

Hi @amir47,
Looks like they have filled the entire area, used the fill as the base for laying the slab for the landing then removed much of the fill once the slab cured.
Personally I reckon you can never have enough air circulation under your house. Can prevent all sorts of issues.
I reckon you could get an angle grinder onto the mortar around one brick (wearing suitable PPE of-course...) and carefully remove it then insert a vent and then pack that in with a little mortar or attach with screws depending on the type you select.

[MitchellMc]

Hi @amir47,

I'd agree with @Adam_W here; air circulation is always a plus. However, it is a small area, and if the rest of the crawl space has good airflow, I'd only go to the effort of installing a vent if you are having issues relating to dampness or poor air circulation. Have you noticed any? The house looks like it has been around for a while, and I'm of the opinion that if it ain't broken, don't fix it. If you are handy with an angle grinder, then go at it. Installation of the vent should only take a couple of hours.

Please let us know if you have any questions.

Mitchell

[amir47]

Thanks guys, 

What do you guys reckon caused that?

It is right beneath stairs.

Are they some sort of soil penetration because moisture/rainwater? or mortar break down then penetration from the top?? Is that means I will have some structure problem later?

[MitchellMc]

Unfortunately, the picture quality and lighting aren't good enough for me to see exactly what that is. I would presume it is the bottom of an elevated concrete slab. My first thought is that it's a concrete slab that was poured on top of the soil and had debris stuck in the bottom layer of it. This would only make sense if work was done to the house later and the soil under the slab was removed. Maybe it was an existing ground level slab, and an addition was added to the dwelling that required this undermining?

What's under the slab is a pile of debris and soil. If you're thinking this all broke away from the concrete slab, I don't believe that is entirely correct. Some of it might have dropped from the bottom of the slab, but quite often, you'll find random piles of building debris concealed under houses like this. However, I'm not exactly sure what's going on here.

Let me mention @Adam_W and see if he has any thoughts.

Mitchell

[Adam_W]

@amir47  as I mentioned in my previous post it looks like the slab was laid on fill & then the fill was removed.
This has resulted in that very rough texture on the bottom. It could also be that where the wet concrete and the fill met they mixed together a little so this made the concrete weaker in that 'zone' and that's what's crumbling out over time.
You can use that fill technique however the fill must be well compacted & then you need to add a layer of builder's film, that heavy-duty plastic sheeting, on top of the fill to keep them separate.
I guess you could monitor this to see if it's an ongoing problem. Perhaps make the area a bit more level and then lay down a plastic sheet and check it every couple of weeks to see if there's material falling down onto it.

[Adam_W]

And a question... what's above the section I have circled?

[amir47]

Hi @Adam_W,

The compartment is underneath of the front stairs, the front door is right on top of the area you circled

[Adam_W]

Hi @amir47 , okay, thought as much.
I assume you found those bricks already knocked out?
Normally you'd expect to see a steel lintel of some sort spanning that gap supporting the bricks as brickwork isn't self-supporting. Or is the slab above that last bit of bricks in the top? Just hard to tell from the pics.

[MikeTNZ]

Hi @amir47,

Does it feel damp where you took the pictures?

IMHO, that has been an add-on that was done on the cheap, no brickie that I know of would install things like that without having vent blocks

in the courses as they were laid, the rule of thumb used to be for every 3 metres of brick course run, you would have 2 vent blocks.

Yes this can be fixed, as others have said, you cut out a block every 7 of them and fit a vent block, this will require the use of a concrete saw, if you aren't confident using a tool like this, hire someone that is, it is not for the faint-hearted.

My advice, at the same time you do this, install a flat galvanised steel lintel of 100mm wide x 5mm thick of a length so that it protrudes into the bricks on each side by 50%.

This will make sure that the foundation wall will not collapse after the vent block has been installed and does not cause subsidence of the building in general.

This lintel can be covered with mortar at the same time as the vent block is installed.

If you have any further questions, by all means let me know.

Cheers,

Mike T.