How to fix a new bigger loft joist to external wall

[perky416]

Hi guys,

I would like to install 6x2 joists in the loft of my 1950's semi to make it more load bearing, however I am having difficulty trying to figure out how to secure them each side of the house.

On top of the external brick walls of my house there are big beams of wood (I think this may be called the wall plate?), it looks like the size of a purlin, I assume its how the whole roof structure sits on the brickwork.
The problem I have is the plasterboard ceilings are level with the top of this wall plate so I cant install joist hangers on the side, and the rafters of the roof rest on top so I only have a few inches gap if I was to rest a joist on top. I could cut the joist to the same angle as the rafters to make them fit, but then the joist would only be supported by a fraction of its original thickness making it less load bearing.

Please take a look at the picture attached, imagine it is a cross section cut of my house. Basically I'm trying to fix the 3x2 joist to the external wall somehow to make it load bearing.

Does anybody have any solutions?

Thanks

 

[cdbe]

Exactly how much can you fit in? It's the centre of the joists where you need the depth. Alternatively can you span the left and right walls a bit further back with a couple of deeper joists bolted together and hang the new joists off these?

The picture should give you the idea (but normally it would go above the existing ceiling joists- but in mine I completely replaced them

 

[perky416]

Hi cdbe,

Do you mean how much length can I get into the gap or the height of the joist? The brace for the current ceiling joists is 3x2, and currently sits on top of a piece of 3x2 to ensure it contacts with the wall plate, so it looks like I can get 3 inches in and 3 inches height, approximately half of the current joist height. I don't think id be able to achieve what you have done as the situation is the same around all 3 external walls of the house. The only wall I could mount to would be the party wall, but then id need a party wall agreement and it still leaves the other side un secure.

Thanks mate.

 

[cdbe]

Yes. This is my other room:

These are 8x2, as you can see quite a bit cut off to fit in. But they are oversize for the span (just had them lying around) and arguably the loading isn't as great as an occupied room as it's just for storage. If by braces you mean binders then they'll have to go - this is where my lack of knowledge hits me - binders brace and strengthen the ceiling - logic would suggest that if you take them out, drop in new joists and fix them to the existing and noggin across the floor this will restore any lost strength - but I've read that the new and existing joists should be kept separate or the ceiling may crack?

In my case as I was replacing the ceilings I just remove the existing joists, binders.and ceiling hangers and put noggins across the new joists.

Also think about your insulation - I now have 200mm fibreglass between the joists and 100mm celotex under - the difference in our 1930's house is amazing - from freezing before to hardly needing to heat the bedrooms now. You won't get much insulation in 150mm joists - over the floored area you could put celotex on top of the joists and board over that.

Unfortunately I can't tell you how much you can safely cut off the joist as I'm just a finger the air guy!

Finally, I don't like it but I believe this is acceptable:

The beam sits on the ceiling joists close to the wall where there isn't much stress in them.

 

[perky416]

Thanks for your help i appreciate it. Im toying with the idea of a full on loft conversion now rather than simply boarding it out.