Concrete Garages, Shelving and Catastrophe

Bison Concrete produced over a million concrete garages for local authorities & stopped making them circa early 80's. When they stopped production at Chadwell, They sold the moulds, for peanuts, to Thurrock Concrete Ltd. who rented part of my builders yard. They then made spare parts for damaged Bison garages for LAs, which was a clever move as it was cheaper than replacing a full garage.

They did not use rebar as such but prestressed the sections with 1/4 inch diameter HT steel "wire". the pre stressing operation was quite technical & the one operation that the owner himself always insisted on doing. A broken overstressed wire, or errant anchor collet, could fly out many yards like an arrow. with serious consequences.

They always advised customers NOT to cut any pre stressing wires because, although they were held in set concrete they could pull back a little causing pieces of concrete to shatter outwards. Drilling a concrete panel can sometimes result in a long crack along the line of the wire, resulting in erosion of the wire at some later date.

I imagine that modern garages are made using the same method

Edited By Sam Longley 1 on 17/06/2020 13:45:37

aluminiumwarehouse.co.uk I have used thier easyfix system of square tube to make racking , a cold frame and shelves. Adding a strategic riveted plate on some corners can be done for a bit of extra rigidity but not always needed.

Sam Longley 1:

Your post about Bison was very interesting to me. I owned a couple of these many years ago and installed a bench across the end of one supported on timbers bolted through the concrete panels. It seems that I was lucky not to have any problems of the kind you describe.

IIRC, these garages were normally available as singles but they could be lengthened by the addition of the modular panels which meant that there could be room for a small car and a modest workspace.

The reason for holes being positioned at manufacture is simply to avoid the erector having to do more than bolt things together and ensure those necessary holes line up! Concrete has good compressive strength but poor in tension - either when drilling thin unsupported sections or affixing things to them.

If parts do not line up, wedges or spacers (shims) are fitted wherever needed. The centre area of panels are much thinner to keep weight (and cost) down, which is why I said I would fix between the vertical joints, from the outside.

All the concrete sections of my garage were pre-tensioned with reinforcing wires, not larger diameter rebar.

IIRC, as visitors, we were not allowed near the pre-tensioned moulds when on site at the local precast concrete works - these were wires stretched over a distance of about 100-150m for railway ‘sleepers’ with several hundred tonnes of tensioning force applied over that length of moulds. Concrete was the usual 40N/mm^2 mix. I expect the sections of my garage are of similar compressive strength.

Structures with smaller panels, fitted between slotted uprights, would have been made like paving slabs - simpler (possibly unreinforced) pressed moulding methods. Those types should definitely not be drilled - either into, or through!

Edited By not done it yet on 17/06/2020 14:10:01

SDS works well in concrete, but will not drill through reinforcing rods. You may have to use a hss drill without any hammer for them. This will ruin the tip of any hss drill, so don't use your best one. As the glue stayed on the concrete, it might be best to glue on some wood that is the full length and width of the straight part of the concrete. Maybe some kind of wood treatment caused the bond to fail at the wood face. A rough surface on the wood would give a better bond.

Edited By old mart on 17/06/2020 14:55:35

Thanks for all the advice. I did take some pictures to show locations, but I've left the phone upstairs during the just past yoga groaning session.

In place here is a terrible drawing

Yes. Someone who still uses paint! Shed is around 8 foot by 16 foot.

The pre-collapse shelves were on a spur uprights on 38x22mm batons. Most were 5 inch wide with the bottom two or three being 8 inches. Even with the mill table fully to the right I can easily get to the wheel. I've emulated some racks with some bits of across the shed where a rack would be timber (the offending batons!) and I simply wouldn't be able to get my hands on the wheel (without the yoga being a lot more successful than I expect, anyway!).

I couldn't see any racking less than a foot deep and although I could make some up from bits of dexion equivalent, it's not cheap and I'd rather spend my money on tooling and raw materials.

I had a chat today with my neighbour and builder who's doing his house up two doors down. As well as suggesting a solution he also gave me some materials to accomplish it (I've got 2 15 foot batons (just) sitting in my shed).

The basic idea is to glue the batons to the ribs as before, but extend them up to the wood frame above the concrete and screw the spur through the batons into the 3x3 at the top. This means I'll have a decent support at the top of the structure with continuity all the way down.

I'm still planning on roughly up the batons on the glue side (the glue stuck very well to the concrete) to help it. Also planning to get some more pressure on them whilst the glue sets, though the exact mechanism isnt' too clear to me yet.

I think this will be safe, but I will keep my ears open for creaks as I mill and be prepared to bound out of the way. Also to minimise any hard things which sit above head height.

I appreciate all the input!

Iain

I had a similar issue. The concrete is as hard as nails. If the sectional garage is the same as mine you will see the sections are bolted in place. Buy some threaded bar/rod and replace the bolt with a longer length of Threaded bar. Have the longer end poking inside. Buy some large sheets of wood and dill holes in line with your sticking out studs. Run a penny washer and nut to secure the panel. Continue until your wallet squeaks. Fix brackets etc to panel. If you are willing to loose some internal volume insert some insulation in the sandwich. Hope that makes sense

keith MM

So here is the result of my deliberations and your help.

The end wall with batons reaching the horizontal supports for the roof. This time I put batons across at the bottom and middle to apply pressure to the glue. Batons at the top fixed with a shortish screw.

Shortish screws removed and spur uprights screwed in

And after a couple of days to make sure it sets, the shelves added and filled.

This led to an uncharacteristic organising spree. But we all have failings.

Iain

Doesn't that roof get a little damp?

When it stops driling sometimes you hit steel regains the drill like a metal drill and turn the hammer off