Cutting wall plate?

[Ian H]

I cut the wall plate on the hipped side of our house to install a padstone and RSJ. Before I did it I strapped the wall plate to the wall with angled straps and also added extra props under the purlins.

Everything went well, I sat the steel on the pad stone before removing the extra props.

I need to do this again and wondered if I should do anything different, maybe fix a straight strap to the underside of the rafters?

Any advice would be appreciated, thanks.

 

[noseall]

Wall plate straps are for holding the roof down and are not there to prevent spread. If what you are doing with the steels and padstones interferes with the roof structures' ability to control spread then you need to take measures to prevent this.

 

[Ian H]

Previously there were just the old 3x2 ceiling joists running front to back and 2 full height 4x4 props under the front and rear purlins.

There was nothing there to stop the side wall plate going further sideways (assuming that's 'spread') and the props are still under the purlins.

I think I'll do the same as the first time but also add 2 straight straps to the back of the wall plate itself.

Thanks for the reply. I'll post back after with how I got on.

 

[vinn]

Why did you need an RSJ in the wall plate position?
What is below the RSJ?
Why not post pics of whats now existing and whats proposed?
Do you have a solid or a cavity wall?

 

[Ian H]

It's to hold a loft floor.

There's not enough room to go under it because of the ceiling height in the bedrooms.

It's a cavity wall, the outer skin is external but will be internal when the roof is extended sideways over a currently flat roofed extension.

That's the best picture I have, it will be to the right of the second rafter.

The rafter look cut because that's part of a panoramic photo.

 

[Ian H]

Vinn, are you saying there could be an alternative to cutting the wall plate?

 

[vinn]

To answer your question: there might be another, or various ways of doing what you propose but I'm not sure enough to give more exact advice.

Its a bit difficult figuring out exactly what you have and what you intend. Can you post properly focused interior and exterior pics?
Can you show more fully what is only partially shown in the above photo - eg where exactly has the plate been cut and where is it intended to cut it?

Where are the joists?
Where are the tie-down straps?
What height do you have from floor to top of the wall plate?
Do you intend to build up another story over the flat roof - and will the old roof space and the new roof space become a single Loft Conversion?

There's good advice above, and as DIY'ers I dont think its wise for you to be making your own assumptions about structural matters. At some stage it would pay to get a SE's opinion.

 

[Ian H]

OK, thanks for the help so far.

The floor to the top of the wall plate is 246cm and the wall plate is 85mm deep.

My pictures have uploaded in the wrong order but here you are.

External shot showing the original house and lower extension with flat roof.

Fist one I did at the party wall side:

Centre on a supporting wall:

Hip end side with 4 straps, cut wall plate:

The second steel wants to be 120cm in from the internal face of the front wall. Which is where I hung this strap:

By the time I have 2 layers of the fire line board under the first steel the finished ceiling height will be 232.

The area over the existing house will be a loft conversion and the extended section of roof over the extension will be storage but to the same spec (floor and insulation) as the loft conversion.

 

[Ian H]

A few more pics of the first steel beam.

The second picture shows where the second beam will sit to the right of the chimney.

 

[chappers]

Nothing wrong with what you have done to the wall plate, but how are the roof rafters restrained as you have now removed all of the ceiling ties.
The side parts of the hipped roof shouldn't spread as they are supported by the hip blades/rafters, and have no loads in opposition, the hip rafters in turn are prevented from spreading by an angle tie across the corner where the two wall-plates meet, which keeps the wall plates in position.

 

[Ian H]

The rafters all sit on 3 X purlins which are 10x2's. They are supported by timbers which were built up from the bedroom floors.

I had to remove one of them so I propped each side with a long acro while I rebuilt a wall then put a piece of 8x4 on top.

By ceiling ties do you mean the old 3x2 ceiling joists? They were pinned to the wall plate front and rear with the last one nailed to the side wall plate at 3 places.

 

[chappers]

a purlin isn't designed to prevent spread although it will to some degree, that is the job of the ceiling joists or ties, they are called ties because they tie the two sides of the roof together, they should have also been nailed into the roof rafters

 

[vinn]

The new photos change things somewhat:

When the extension roof goes on it will eliminate the hips & the jack rafters, and the old roof common rafter plane will come through with further common rafters, & a new length of ridge.

Given its a loft conversion then collar ties would presumably be too high to be effective - for what they would be worth in the event of movement. So, as above, what do you propose to prevent any possible spread?

Was this business designed by a qualified person?

 

[Ian H]

The extended roof will include a longer ridge and the hips will be moved outwards. The purlin on the rear will be removed and a dormer installed.

The drawing were done by a CIOB registered 'technician'. The beams were calculated by myself using the online Steel Beam Calculator.

Being a DIY'er I plan to employ a brick layer to raise the extension and a roofer to install the main structure of the roof before I felt and tile it.

I have no idea about the spread. I reinstated the 3x2's that were pinned to the wall plate (but not the rafters) by bolting a timber into the rear of the RSJ and connecting like this:

 

[vinn]

You've lost me - I was under the impression that you were extending the floor level & the roof plane over the extension (presumably "the hips will be moved outwards" means the extn roof will finish with a hip?) now you talk of a dormer.

I earlier noticed a few stubs of joist but are you saying that that is how both wall plates will now be tied into the steels?
All this and knowledge of spread are simple knowledge for any qualified person - your technician seems a bit amiss?

AAMOI: the keyed-in join of the new extn brickwork to the old brickwork has developed aa opening thats been pointed up -
just to the right of the down spout - perhaps the down spout was dropped there to divert the eye?