Fixing joists to deck posts

lee171181 · 2 May 2013

Hi I'm constructing a raised deck and have 6x2 joists that need to be fixed either side of a 4x4 post. this will give a total of 8 inches. What would be the best option for fixing these, - everyone says coach bolts, but what ones/type?

Should I be looking for a bolt that goes through the whole lot at once i.e. joist-post-joist, or should I fix each joist individually either side using screws (coach screws maybe?)

thanks

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rjm2k · 2 May 2013

I assume it won't be visible and doesn't need to look pretty?

I'm building decking at the moment and have just been using 3 screws through the joist into the posts for this, easy to adjust a little for leveling before committing. The decking came with a box of 5mm x 100mm screws so I believe that's what they expected me to use.

With bolts you would have to pre-drill and get it perfect first time.

But I'm no expert and am building it for the first time.

lee171181 · 2 May 2013

I was thinking about screws but as its supporting a raised deck I need it to be strong so think a coachbolt would be better but just not sure which type to use, or maybe something different all together?

No it wont be visible so don't care what it looks like!

lee171181 · 2 May 2013

Would this be suitable?

http://www.toolstation.com/shop/Scr...ts/Coach+Bolt+Nut+M12+x+240/d90/sd1670/p10853

WabbitPoo · 2 May 2013

Use these

they come in various lengths. i rarely bother with bolts any more and i build a lot of decking.

lee171181 · 2 May 2013

Will these be strong enough tho to support a raised deck?

Some of the posts are concrete so I will
Need to use a coach bolt for those, - will the toolstation ones suffixe? do they really need to be the expensive external ones?

freddiemercurystwin · 2 May 2013

Here you go lee, these should be man enough!

http://www.ebay.co.uk/itm/M30-Hexag...rial_Nails_Fixing_MJ&var=&hash=item2c6e815375

rjm2k · 3 May 2013

freddymercurystwin said:
Here you go lee, these should be man enough!

http://www.ebay.co.uk/itm/M30-Hexag...ls_Fixing_MJ&var=&hash=item2c6e815375[/QUOTE]

You could probably support a house on those, never mind a bit of decking!

kingandy2nd · 3 May 2013

lee171181 said:
Would this be suitable?

http://www.toolstation.com/shop/Scr...+Bolt+Nut+M12+x+240/d90/sd1670/p10853[/QUOTE]

Yeah I'd used these type of bolts for your decking.

When I did mine I fixed the timbers together with 100mm screws to ensure everything lined up properly and was level before drilling the holes for the coach bolts.

Worth investing in one of these too if you don't already have one:

http://www.screwfix.com/c/tools/auger-bits/cat4620420

lee171181 · 3 May 2013

kingandy2nd";p="2758432 said:
lee171181 said:

Worth investing in one of these too if you don't already have one:

http://www.screwfix.com/c/tools/auger-bits/cat4620420[/QUOTE]

Thanks, - I assume a 12mm bit is requited for an M12 coach bolt is that correct?

Do you think those Toolstation bolts will be strong enough as the description says they are for low load bearing applications & are not really external ones?

Click to expand...

kingandy2nd · 3 May 2013

M10 or M12 will be plenty strong enough for a deck. Make sure you get washers too as those toolstation ones don't look like they come supplied with them.

Could always opt for these ones if you need around 50 of them (not sure how big your deck is, but you'll need 2 per post) as these are galvanised.

http://www.ebay.co.uk/itm/M10-x-240...uts-Washers-per-50-/220976939701#ht_430wt_719

Yes, the M number relates to the diameter of the screw/bolt in mm so M12 will need a 12mm drill bit.

freddiemercurystwin · 3 May 2013

A single low grade M12 coach bolt like the toolstation one will theoretically shear when about 1300KGs is applied on it, I think you'll

They look galvanised though it doesn't actually say so, if so it will be fine outside. Might be worth ringing them.

Have to say if I was gonna go with a bolted solution I would use traditional bolts rather than coach bolts at least you'll never get any issues with them slipping or if you ever need to take the deck apart.

Khalid1 · 3 May 2013

I used a 100mm screw from screwfix specifically designed for external timber.

lee171181 · 3 May 2013

freddymercurystwin said:
Have to say if I was gonna go with a bolted solution I would use traditional bolts rather than coach bolts at least you'll never get any issues with them slipping or if you ever need to take the deck apart.

I cant find a traditional bolt long enough though to go through the 8" unless a threaded bar would be an option?

Would coach screws or the TimberLok screws be just as good, or is a bolt through the whole thing a preferred method? I just really thinking about the strength really

dhutch · 3 May 2013

While a pair for bolts or threaded bar and a nice thick spreader plate, or even a steel hanger, would be very nice, I have to admit I would be very tempted to just fire a stack of large screws into it.
- If your worried about the durability/load you could fire them through some perforated plate, and or , apply a squirt of polyurethane glue.

A larger portion of the force will be transmitted via friction between the two, rather than purely on the shear strength of the fixing alone.

Daniel

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Fixing joists to deck posts

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