Steel beam and padstone

[Sarah150]

building an extension with bi folds. 4.8 metre bifolds.

Nightmare of a SE.

SE said put bifolds on steel 0n inner leaf, builder and bifold people say outer, due to damp. Steel people say they will weld plate to bottom of steel to allow for bricks above the opening for the inner leaf for doorway. My query is if I have to have a padstone in outer brick leaf, SE doesn’t mention, but builder says you do. How is this not visible? On inside you won’t see it. Confused.

Help.

 

[Bonni]

Been there, done that.

Padstone on inner leaf, brick outer. 80mm plate fabricated to outer beam with fabricated web's at centres specified by SE.

If you fit on the outer leaf, YOU CANNOT drill up and must fit cleats. Also, vertical DPC MUST be positioned correctly, sealed to outer edge of doors before trimmed off.

When I do extensions, I recommend fitting doors and windows in the cavity.

 

[^woody^]

but builder says you do.

You don't.

Is your builder a real one or just masquerading as one?

 

[tony1851]

As long as you have a reasonable bearing - say 200 -250 - you do not need a padstone on the outer skin; in any case that would look awful.

 

[Sarah150]

Thanks.

Luckily they have changed their minds to steel on outside, plate to inner. Padstone too, but there are bearings of 300. Hoping brickie will kmowmanout how to do the dpc bit!

 

[Ian H]

I thought the steel went in and plate out because the inside wall has the weight of the floor and roof on it too?

 

[DIYer Damo]

For my single storey extension with bi folds (4.2m) It was steel to inside leaf with padstones and plate welded to bottom of steel 800mm wide which reached external leaf. External built out of Fibrolite blocks - no need for any padstones. Bifolds bolted directly to steel plate and sat halfway into cavity from outside leaf. All drawn up by SE and passed by building control.
If yours is a Two storey extension it might change things?

 

[^woody^]

Luckily? Lol

Unlucky more like.

They seem to be a bit clueless about basic construction and just making things up as they go along. There is a concept, traditional i know, but has worked for a few years, and that is that someone draws plans and someone else sticks to them.

Now you have all the loads going on a thin plate that was not designed for the loads, and an ugly exposed steel on the outside that needs hiding in a risky way, whereas it should be on the inside where it can be covered easily.

 

[tony1851]

This is how it should be done (stiffening gussets not shown).

 

[John D v2.0]

How you you insulate the steel plate there that goes through the insulation layer? To prevent a thermal bridge.

 

[tony1851]

You glue a strip of insulated plasterboard to the soffit of the plate.
Also, you pack fibreglass insulation each side of the web and up against the cavity tray.

 

[John D v2.0]

Got it, so effectively put the beam on the"cold" side and insulate it well. Presumably you put a decent vapour barrier on the warm side of the wool too?