purlin depth

[juliouno]

Sorry if this has been covered already. Just wondering how deep a new purlin should go into the party wall, I assume that is should go 1 brick deep (so about 100-110mm). Is this correct? Is this something that the SE should specify?

Cheers

 

[noseall]

Sort of correct yeah, just your terminology.

One brick thick = 215mm.

Half brick thick = 102.5mm

 

[terrypin]

Pad stone?

Party wall act/agreement?

 

[juliouno]

I have got a party wall agreement, so that is all in place.

Are padstones really necessary to get it passed through building control? I thought they were more of a RSJ thing.

So noseall you are saying that it has 1 brick thick or half a brick thick. I am assuming half a brick thick (102.5) is what is required, because 215mm would go through to the neighbours place!

 

[terrypin]

Think about it, RSJ and purlin, any similarities in function?

I would prefer the load spread on a pad stone than a brick.

IMHO.

 

[catlad]

I have seen hundreds of purlins in my working life and most of them have been sat on a single brick party wall.

 

[terrypin]

I have seen hundreds of purlins in my working life and most of them have been sat on a single brick party wall.

I am not saying they don't, in over 30 years and 100's of roofs I have seen the same. I have also had to replace a few purlins and repair a fair amount of party walls.

Like I stated it's only my opinion and preference that a pad stone be used, it is also a practice undertaken by a lot of contractors and during renovations.

 

[theoldun]

Catlad is right.
Timber purlins either vertical or angled to roof pitch do not require a pad stone.
Regards oldun

 

[tony1851]

+1;
the reaction of the purlin on the wall is not actually that great. Tiled roof dead loads are typically around 0.8kN/sq m, compared with around 5kN/sq.m. for traditional cavity walls.

 

[juliouno]

Just had the BCO officer round and he says said that the purlin needs to go 4" into the wall and rest on a padstone to pass building control.

Should the padstone be laid horizontally, which would mean only the corner of the purlin will be touching it or should it be laid so that it is on the same angle as the purlin (About 43 degrees)?

Cheers

 

[tony1851]

The padstone should be horizontal - although technically a knife-edge of the purlin will be resting on it, the sides should be well-packed up with cut bricks.

But your BCO appears to know nothing about these things - you don't need padstones with timber purllins. So you must jump through this hoop to satisfy him.

 

[theoldun]

Tony is 100% right, there is nothing what so ever in BR to state that pad stone is required under a purlin.
If we had been in your position, we would have politely told him to either p8ss of or quote the regulation.
Regards oldun

 

[catlad]

I find it odd that you are not going to fit the purlin vertical so it sits flat on your wall.

 

[juliouno]

Ah we are installing a steel purlin, not a timber one. the timber one would have had to have had a 400mm profile according to the structural engineer (ridiculous). So maybe that is why he is insisting on a padstone.

It would be far easier to install the purlin so it was vertical, but then all the loading is on a very small point of the purlin.

I need to bed it into the wall both ends 100mm (4"),on a padstone. What is the technique for actually getting the purlin into place with 4" sunk in either end, without going through the party wall to the neighbours place (which wouldn't be popular). Because the wall is in the way of being able to slide it in to place.
The wall is 1 brick thick (i think) in English party wall bond.

 

[catlad]

Now I feel like asking a lot more questions!