I have just finished erecting my new greenhouse and now have to anchor it to the concrete flags on which it stands. This involves drilling through the galvanised flange of the base into the concrete flags below. What kind of bit do I need in my drill? A metal bit to go through the metal and then a masonry bit thereon, or will a masonry drill go through the metal as well?
Don
No.
This can be difficult as most masonry drills will be blunted by trying to drill through metal with them and a metal drilling bit will be blunted when you hit the concrete flags under the flange.
Can you get a little clearance between the flange and the concrete, with a crowbar underneath the flange for example? If so lift the flange with the crowbar and put a sliver of wood or something in the gap. Then drill the hole in the flange with an ordinary HS drill doing your best to stop when it's through the metal so that it doesn't hit the concrete. Then drill the hole in the concrete with a masonry drill.
Next time drill the holes in the flanges before installation! :-)
There are 'universal' drills which are supposed to be able to drill through all sorts of materials, one of these might be an easier solution to your problem if you can get one in the size that you want.
If you have an sds drill then just use an ordinary concrete drilling bit, the flanges I have seen on greenhouses are so thin that an sds drill will go through with no problem. In an ideal world you should drill the flange with an HSS drill then the paving slab with a masonry type, but the real world just whack it through, unless the flange is thick you won't hurt the drill bit at all.
mrcheerful
Oh. Thanks.
Don
I can see now that the holes should have been drilled in the base flange first. The author of the erection instructions obviously didn't. I shall take the glass out of the walls to reduce weight and follow your advice of putting a sliver of wood under the base. Thank you.
Don
I don't have an SDS drill (not even sure what that is) so will insert a sliver of wood between the base and concrete and use both types of bit as suggested by Chris Green. Thanks.
Don
Or drill the slab just inboard of the flange and use a "penny washer" (aka repair washer) big enough to clamp the flange. Doesn't damage the galvanising, and easier to get the drill vertical.
If the flange is really thin it may be possible to punch a hole in it with a nail or some such. As long as there's a bit of a hole a masonry drill will probably survive.
Push hard on the masonry drill to prevent it just spinning on the metal and getting hot, that's what will destroy it.
Even if the same drill could be used for both, wouldn't you want a smaller diameter hole in the flange, given that you'll presumably be using some sort of ragbolt (or whatever they're called) or a plug in the concrete?
J> I have just finished erecting my new greenhouse and now have to anchor
That would be great, but I didn't mention that the flange has a lip on it to give the base added strength :-(
-- Don
I've done one hole successfully using the sliver of wood method. The flanges (top & bottom) have lips on them for extra strength which made it difficult to hold the drill upright. The steel is far to thick to punch a hole in. Isn't there a way to stop the drill skidding about by sticking a piece of duct tape or something over the area to be drilled?
I can see that I will have trouble in getting the screws in as well. I've been provided with 10 x 2" wood screws & rawl plugs to be placed three each side of the 8' x 6' base and two each end. Since I can't budge the greenhouse with just the 3mm toughened glass in the roof. I can't imagine the wind shifting it with the side grass fitted as well. I'm wondering with there isn't a heck of a lot of overkill here.
Don
Duct tape - no. Nice hard pointed punch, heavy hammer (lump hammer perfect), one strong blow. Result: dent, deformation, "drill settles here" feature.
Wind is quite energetic when it blows hard; and the slab side of a greenhouse will catch it full on should the wind blow from the right (wrong!) direction. Your greenhouse mfr specifies the ground fixings to allow for strong wind from said direction with greenhouse unscreened by trees or anything else close by. You may as well fix the damn thing down good and strong according to the mfrs calculations - you'll feel pretty daft if the thing does tip over next time we get a Michael Fish blowing up from the sou'west ;-) 2" deep screws doesn't strike me as being any kind of "overkill" - if it were me I'd be tempted to use frame fixings or longer screws, if anything!
Stefek
Hefty whack with a centre punch.
So you'll have to drill oversize holes to get the plugs in, and fit washers on the screws.
It's that one strong blow with the lump hammer that worries me! But you are right in what you say. It would be too much of a risk, even though Michael Fish has retired.
Don.
I shall do both. Thanks.
Don.
Ah, you need the Mk II special version then: a short length of something vaguely channel section, inverted so that one leg reaches over the lip, and the other bears on the concrete, drilled for the screw. I'd draw it, but ASCII art is beyond me at the best of times, and when your keyboard can't manage one of those "not" things (vertical bar) it's not even the best of times.
__ __ +--------\ || /-------+ | _______| |______ | | | | | _ | | | | | | | | | | | | | | | |__|_|_______ |_| | | |______________ ==================| |=======================
If you have an inwards facing flange all the way round can you not lay paving slabs or whatever on top of the flange to anchor it down without screwing ?
AWEM
Just buy a stock of cheap HSS bits and use them to drill the flange, then a masonry bit for the concrete. When one HSS is too blunt to use anymore (from hitting the concrete) use another...
MBQ
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