Yeah, I know. I'm relying the fact that we live on a hill, and that after a big thaw and then loads of rain, there was just surface water in the pit. Under the clay it was dry. The sheeting is 4m wide and the pit is 1m wide and 1.5m deep which makes it 4m down one side, across the floor and back up the otehr side. This means there are no joins below the top of the pit wall. Where there are joins on each side - they are 600mm over laps with two beads of sikaflex rolled with a roller and then taped with DPM tape. I've double skinned the dpm in the pit as well and am using extra thick (1200ga) better quality DPM.
I know it's not true tanking, but any water has a long way to go, and if the worst does happen, I have a nice sump with a submersible pump.
The big question now, though, is what thickness timbers to use for the boards that will go over the pit? Thick enough to support a car, but light enough to be manageable. The pit is 3.5m long, so there will be a few of them!
A given board will only ever have to support a single wheel at any point in time, so I reckon no more than 500kgs (Front wheel of a large car).
Anyone know anything about the loading of timbers?
I'd be tempted to weld rebar into a grid and then top it with chequer plate. If you do it in small sections then you can remove them as plates. You will need less of a recess at the top of the pit as the sections will be thinner than if you are trying to accomodate 6 inch timbers. And as you're such a rebar star.
Just make sure the timber is of a good quality (don't buy the cheapest crap ) remember that it will be laid in it's weakest direction. Personally i'd be looking around the 70mm ish wide joists as a minimum a good timber merchant should be able to provide you with strength test for joists
I did consider getting timbers drilled through and then inserting reinforcement into them. Seems extreme though.
Not sure how strong just a mesh of rebar would be - might want to bend.
Another thought was rectangles of 50mm square section with 13mm ply on top. In fact I like that idea a lot. In fact, even 50mm angle might do it.
Nice job done there Nick
Lolled at you movie
Just need to be sure I don't do this...
have you left a channel at the edge for you planks to sit in and be flush with the floor?
id be tempted to use scaffold planks that run from side to side (like the slats on a bed)
yup there will be a step around the edge of the pit in the concrete that will be 150mm deep and 100mm wide. This means that 150mm is the thickest I can go, but I hope not go as thick as that. I'll run a timber along the length of the step to make up any difference.
Hmm, not sure if scaffold planks inspire enough confidence.
What's the width of the pit Nick? I have a table here from the floor loading calcs I did for a half floor in my garage. They're domestic based though, on a imposed loading of not more than 1.5kN/m2
Example:
If you space 38x122mm joists at 400mm intervals, you can span a 2.37m gap and support the above loading.
Ooh, might be useful
The pit is 910mm wide and then a 100mm lip to pick up on at each end.
So, if you want to span a 1.1m gap, with the biggest gap (600mm) between joists, the minimum size joists you would need of C16 stamped timber are 38 x 97 mm.
That presuming you then cover the joists with a flooring grade covering, like T&G chipboard.
So we're looking at 4" timbers really.
Am starting to come round to the notion "boards" that are 300mm wide, made from a steel frame with a ply surface.
Building control man came this morning and approved my rebar. He wanted to know why I had used T16 in stead of the spec'ed T12.
"It's T12." I said
"No, that's T16"
"Well, I ordered 168m of T12, and 168m of T12 arrived. The holes in those jigs are 13mm, so I'd be impressed if it was T16"
"Are you sure"
"Yes, here's an offcut"
"Ah, now THAT'S T12, but the stuff in there is T16"
"I promise you, it was all the same size"
"You are sure?"
But the good news is he's happy for now
Some more progress today. The floor in the pit went in
Having worked extensively in a pit I always thought it would be a good idea to incorporate some lighting into the structure if I ever built one something like a couple of strip lights sunk in either side of the pit with a removable bit of perspex over the top, are you thinking of doing anything like that?
First two courses of blocks have gone in Really starting to feel like something now Also put a hold in the bottom course to allow for my ventilation. This will run up behind the block work and then under thew concrete base and then up the back wall to an extractor fan.
Also, put into place all the services as they'll need to come in though the slab.
I have electric in, network in, cold water in, hot water in, waste out, sump-pump out. Think that covers everything, but if anyone can suggest anything else, then shout out! I have thought that a smoke alarm that is hooked up to the house would be useful.