drywall screw size

[marsaday]

I need to go through 50mm insulation board and 12.5mm plasterboard.

Are the 75mm drywll screws big enough or do i need 80mm?

 

[Richard C]

Even 80mm is too short really; 85mm would do but the nearest you will get to that is 90mm I think; assuming your battens will accommodate them.

 

[marsaday]

i will be going into a 100mm rafter so should be fine.

i dont think screwfix do bigger than 75mm. any ideas where i can get these from.

 

[Chukka63]

im currently on a loft conversion with the same spec below the rafters and have opted for 100mm screws.why scrimp ona few quid for total piece of mind???.

 

[marsaday]

ok i will get 100mm, but where can i buy them from and what is the likley cost

 

[Chukka63]

your local builders merchants or screwfix etc.diff makes mean diff costs.google screwfix for reference.

 

[Richard C]

Take your pick;
http://www.google.co.uk/search?hl=en&source=hp&q=100+mm+drywall+screws&meta=&aq=0s&oq=100mm+dry
Also worth checking sometimes is a B&Q trade centre & Wickes who stock more than you would think & often do promotions. I always look out for their bulk pack deals of 40mm & 50mm (not sure about they stock 100mm though) & stock up with several packs very cheaply whenever I can. I hardly ever bother with the 3 big national BM chains who are mostly rip off merchants rather than builders merchants; Ive found TP are usually the best of the bunch when it comes to getting a realistic trade discount, particularly if you dont have an account.

 

[Chukka63]

strange cos i never bother with TP as theyre always miles more expensive.Buildbase is generally the cheapest around here and make less cock ups than Jewsons.

 

[marsaday]

Agree the big BM try and rip you off. however i have got some good prices off TP for my loft conversion. however i have been to a different branch today and they have given me not so good prices on more stuff i need. so i will go back to the other depot i went to last week (simply passing by the other depot today so called in to get some prices).

for eg. 75mm drywall screws (250) = 8.53 plus VAT. not that good really.

thanks for the link !

 

[marsaday]

Whats the difference between black screws and zinc ?

 

[PrenticeBoyofDerry]

the black screws are zinc

 

[marsaday]

ok, but what is the difference between the black and the silver. or fine and coarse. I take it they are for different jobs. So which is used where?

 

[PrenticeBoyofDerry]

Black phosphate and Zinc phosphate, they are corrosive resistant, they do the same thing!

Fine for metal
coarse for wood