Attaching joist bearers to vertical posts

[coylumbridge]

I have a an existing raised patio (about 800mm at highest point) going out from the house; 14' x 14'. I plan to deck over it using deck timbers as "bearers" screwed to the existing slabs at 400mm centres with decking running perpendicular to these bearers.

I also want to extend it from one side going out by 1.2m over about half the side, ie 7'.

For this extended part, I plan to do 3 concrete footings at each of the outer corners and halfway along the 7' and use bolt downs to out in 90x90mm posts which would also be balusters. I want to attach cross members about 1.2m long (6x2) between these 90mmx90mm posts and the patio wall so that I can then run 7' 6x2 joists perpendicular at 400mm centres.

I plan to rawlbolt 4"x4" vertically on the 800mm (countersink rawlbolt anchor M10 75L in about 25mm) to the wall then bolt the 6x2 cross members to the 90x90 posts and the 4"x4" which is bolted to the wall. I thought about using two 200mm or 220mm exterior grade M10 coach bolts to secure each end of the cross member to each 90x90 and 4x4. Could you tell me if you think this is OK please to use coach bolts in this way as they'd be joining the joist bearers to the sides of the posts and, therefore, be taking a load ?

Joist hangers won't work as they'd be too near the top of the wall. Same for a wallplate which would need to be very near the top of the wall.

Thanks

 

[megawatt]

It's common practice to do as you describe so I wouldn't worry though I generally use M12 bolts for beams.

I also prefer to only hang on coach bolts when there is a beam either side of the post but that's just personal preference really.

You can always rebate the top of the post and sit the beam in and then coach bolt the lot together also if you wish.

Many ways to remove the fur from the feline.

MW

 

[coylumbridge]

Many thanks Megawatt.

Hadn't thought about rebating the top - good idea.

Reason I went for M10 was that Screwfix only seem to have M10 in exterior coach bolts but I'll have a look for other suppliers.

Cheers

 

[megawatt]

Loads of suppliers online ...

http://www.tbsmerchants.co.uk/cgi-bin/build/product/IRCO_Coach_Bolt_Nuts_M6_M8_M10_M12.html

As one example.

Happy decking

MW

 

[WabbitPoo]

Do I understand correctly that you intend to screw your joists to the existing patio? If so

a) its a waste of time
b) if it's slabs, then don't. See a)

Your frame should, by all means, bear upon the patio if it is solid.

 

[coylumbridge]

Do I understand correctly that you intend to screw your joists to the existing patio? If so

a) its a waste of time
b) if it's slabs, then don't. See a)

Your frame should, by all means, bear upon the patio if it is solid.

Thanks wabbitpoo but don't worry - I'm not doing it this way.

 

[WabbitPoo]

I plan to deck over it using deck timbers as "bearers" screwed to the existing slabs

You'll understand my confusion........