Removing Collar / Rafter Tie

[jagillham]

Hi,

I have a 1950’s semi, with a generous loft approx 6m long.

There is 3 supports on the loft, which I believe are either called Rafter or Collar ties which divide the loft into quarters. The one in the middle is around 3ft height, which results in an awkward limbo or high jump. If I could just remove that I could get to probably 75% of the loft without any acrobatics.

Not expecting anybody to give exact structural calcs, but would anybody be able to say if possible to remove, and what kind of solution / cost would be involved?

Thanks!

 

[^woody^]

No you risk the roof sagging.

Unless there is a wall right below the purlin, on to which you can fit a vertical strut and can brace this back to the eaves.

 

[jagillham]

No you risk the roof sagging.

Unless there is a wall right below the purlin, on to which you can fit a vertical strut and can brace this back to the eaves.

Thanks, to be clear I’m not looking to remove the the struts, just the horizontal one.

 

[^woody^]

Thanks, to be clear I’m not looking to remove the the struts, just the horizontal one.

The collars are restraining the angled struts. They act as one, one is pointless without the other.

 

[jagillham]

The collars are restraining the angled struts. They act as one, one is pointless without the other.

Ah ok, they are not actually attached to the struts or the purlin, then are nailed into one of the rafters only.

There is a wall below one side, but not the other. Are there other solutions?

 

[jagillham]

A couple more pictures to show the arrangement.

I’m wondering if they are required, if I could replace with either one above, or below (or both) to achieve the same affect?

 

[^woody^]

You can't move the collars or the struts. They are fixed like that because there is nothing below them to take any loading.

There are ways, but someone who knows what they are doing needs to design them.

 

[jagillham]

I

You can't move the collars or the struts. They are fixed like that because there is nothing below them to take any loading.

There are ways, but someone who knows what they are doing needs to design them.

I take that to mean getting a SE involved etc? Didn’t really want to spend much on it.

I’m going to be bringing the floor level up anyway to get my 270mm insulation in, so maybe a step either side too would make it a bit easier to get over!

Thanks for the advice.

 

[^woody^]

The general concept with a roof is that it is framed, and each piece restrains or supports another so everything acts as one.

So pieces can often be removed as long as other pieces are put in to transfer the loadings elsewhere.

Upshot is that it's not always an engineer that is required, but it needs to be someone with experience in roof framing and triangulation. But an engineer may give you more piece of mind.

 

[catlad]

Measure the distance between the purlins and take it out, if that distance changes put it back.
Make sure the purlins are fixed to the diagonals first.

 

[Leofric]

Measure the distance between the purlins and take it out, if that distance changes put it back.

is that a serious comment Don't take them out ,they are structural components. Building regulations approval is required for structural alterations including roof structures .

 

[catlad]

Well if you cut a piece of say 4x2" half an inch short of the gap between the purlins, you can then lay it on the top of the diagonal beams so when you remove the horizontal beam you can see if it becomes tight then its probably best to replace the horizontal beam.