Best drill bit for concrete

[dilly]

Hi
Just wondered what is the best drill bit for a sds drill,I have to drill about 200
Holes.it needs to be quiet long around 250mm and a no 5mm.
Thanks

 

[Norcon]

Buy two or three standard sds bits.
Never seen a 5mm that length though and seems odd to need to go that depth in 5mm.

 

[dilly]

I only need to go about 40mm into concrete,installing a warm roof onto concrete base so insulation is 120mm 18 mm ply.unless anyone has any better ways of mechanical fixing.

 

[ntb]

Is your plan to put a fastener through the ply, insulation and into the concrete? I'm picturing a 1930's outbuilding with a poured concrete slab roof? Give us more information because I'm not convinced that's the best way to go about it.

 

[dilly]

yes thats about it,no idea ho old the roof is though

 

[ntb]

Right. Well I would frame the perimeter with timber and build a box section deep enough to accommodate the insulation fastened to it. Depending on the span, I would either use joists or build up centre supports (also fastened to the concrete) for the ply. On top of that, I would take the opportunity to put a slope on it for better drainage.

Having said that, personally I would put a proper pitched roof on it but that's another ball game.

 

[dilly]

Hi thanks for your reply,i had thought of doing that,but it means fixing twice
and buy the time you have put in the joists to bring it to height you are going to need a good few and then i would have lost the point of the insulation as there is going to be alot of joists because of the amount of fixing i am going to put in.
i hope that makes sense

 

[ntb]

You wouldn't put any fixings through the insulation using my method, it would just sit there. It would have to be a pretty small area for the framing to make up a sizable proportion of it.

What fixings are you proposing to use?