Joist fastening query for flat roof - bolts (type, number of etc)

[shd1970]

Can anyone advise on the following please

I'm link detached and i'm extending my flat garage roof forward
Plan is to bolt a 120 x 47 C16 joist to each wall and then use joist hangers at 400mm centres

The photo attached shows my house and the blue lines show the approx position of the joist to marry up with the existing horizontal. This joist will be approx 2.8m in length

So my questions are :

• Is there a rule of thumb for the number of bolts required per Xm ?
• What type of bolts are best (throughbolts or rawlbolts)
  
• Is there a particular size of bolt that i should be looking to use ?

With regard to bolts, I found this guy on Youtube :

...and at 3m30secs the guy presents a table showing load weightings for the M8 that can take 3.0kN (=300KG force)

Considering the roof will only be walked on for maintenance, would a number of these be suitable or best go for a larger bolt ?

Its worth mentioning also that my bricks are London Heathers if that makes any difference

And my final question :

• If i should equally position the bolts, am i safe to drill above the door as i'm guessing that i will hit most likely a concrete lintel or best to avoid if possible ?

Many thanks in advance

 

[^woody^]

https://www.diynot.com/diy/threads/what-kind-of-bolts-and-size-timber-should-i-use.537586/

 

[shd1970]

https://www.diynot.com/diy/threads/what-kind-of-bolts-and-size-timber-should-i-use.537586/

Thanks woody !

so something like these ?
https://www.screwfix.com/p/fischer-...=1050828#product_additional_details_container

I had originally been looking at Rawlbolts but i think i have just seen the material difference being that with the sleeve anchors, you can use the same drill size for the timber and brick, correct ?

2 final questions if you would be so kind :

• You say a bolt every 600mm.....what about above the door please due to the possibility of a lintel. Can i put one here or best avoid and go as close as i can either side ?
• Do the sleevebolts have to go into brick or could they go into mortar ?

Thanks again Woody, much appreciated !

 

[^woody^]

I thought rawlbolts, sleeve anchors and expansive bolts are all one and the same. Or 'Through bolts' which are nuts on a threaded bar rather than bolts. All these have the same hole through the plate and the wall.

Always fix into brick not joints. However with those London bricks, they may be frog down, so try about 1/3 down. Otherwise 1/3 up!

You can drill the lintel of that's how it works on the spacing.

 

[shd1970]

I thought rawlbolts, sleeve anchors and expansive bolts are all one and the same. Or 'Through bolts' which are nuts on a threaded bar rather than bolts. All these have the same hole through the plate and the wall.

Always fix into brick not joints. However with those London bricks, they may be frog down, so try about 1/3 down. Otherwise 1/3 up!

You can drill the lintel of that's how it works on the spacing.

thanks again Woody

I will drill a test hole somewhere else to check, but that assumes that they are all laid the same way

regarding the lintel, the doorway is 900mm wide so will definitely need to drill it

The 600mm spacing.....can you educate me as to whether that is to meet an actual building standard of some sort, or just from your obvious wealth of experience and expertise please ?

 

[^woody^]

Normally the bricklayer will be a frog up or a frog down person, so the bricks won't generaly be randomly laid.

By the looks of things, above the door there is a tray lintel on the external so you won't be drilling into concrete, just the bricks.

Fixings will normally be dictated by someone somewhere doing some calculations. But over the years for common situations, a typical specification is known to work and so becomes standard. It's not just the loading, bu also spacing prevents any twist or bowing of the timber, so for bigger timber say, the spacings would be reduced but thats not for extra loading, but to keep the timber flat on the wall.

 

[shd1970]

thanks Woody

those lighter colored/badly matching bricks were evidently as a result of the double glazing company being unable to use a tape measure as they measured wrong and brought a smaller door and the previous owners accepted it (yep, true story !!!) so those bricks are effectively just sitting on the plastic

So, its the above 2 rows of heathers that i propose to drill

I assume that first course of heathers above the door are the ones sitting on the tray that you mention and are still ok to drill/fasten too, or is the top row a better choice ?

 

[^woody^]

The upper course would be better - less chance of the brick cracking