Filling a pit in garage

[Bruceslades]

Hello all. First of maybe a few questions.

I'm converting a detached garage to room. It has a pit in it. 2400 long by 800 wide. It is 5ft deep has a cement bottom and brick sides. It has been in the garage for about 50 years. I am going to put a floor on top of th garage concrete floor - 75mm kingspan and a 18mm t & G chipboard. I need to make sure that the pit is safe and so I have put joist hangers every 400 and then 50 x 150mm CLS. I was going to put some OSB on top and then self level to the garage floor level - about 10mm. I am now having doubts that I have done the right thing.

Should I have infilled it with rubble or hardcore and then concrete? I am confident that this is strong enough to walk on as I have done it but I am just worried that the pit could one day collapse inwards. It hasn't moved at all in 50 year I think. Am I being over cautious?

Cheers in advance for any help with this one.

 

[freddiemercurystwin]

Theoretically building control would not allow a compacted hardcore solution as it may sink over time, you're joists will be fine, is the pit dry? Theoretically the void should be ventilated. What's the self level going to achieve? I'd use ply on top of the joists.

 

[Bruceslades]

T2hanks @freddiemercurystwin for the reply. That's good news as it will save me some time there.

I was wondering about ventilating the void but it's going to be impossible I think. The pit is dry ie it never fills with water however the bottom is damp because a washing machine has been leaking nearby and some water trickling in. I was wondering whether to put some dpm on the floor or tacked to the bottom of the joists. I have also treated the joists. As far as damp and mold is concerned the only issue is can see is it affecting the joists and the board above, but I'm guessing that it wouldn't be significant enough to cause problems.

Using self levelling because the top board will sit 10mm below the garage floor level once it is done. There was a lip around the top of the pit where the sleepers that covered it sat.

 

[^woody^]

Fill it with hardcore, and cast a reinforced concrete slab across the pit walls to deal with any potential settlement

 

[tomfe]

Keep it and turn itto one of those posh wine cellars.

 

[Bruceslades]

Keep it and turn itto one of those posh wine cellars.

Don't tempt me.

Filled it today with a lot of hardcore a friend of mine had and then chucked a DPM over before screwing 18mm OSB to joists. I reckon it should be fine, it hasn't had any movement in 60 years. I do have another problem relating to the garage though so I will create a new post...

 

[garyo]

Exactly what I thought. Make a feature out of it somehow. Even if only to make the next owner think 'mmm that could be a wine cellar / panic room / love dungeon'

 

[freddiemercurystwin]

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