Loft Conversion - thick beams runnning length of house

[405 TD Estate]

In the loft in my (end of) terrace house the end of the roof is square (not slanted like a semi-detached house).

Inside to support the wooden uprights is a long beam on each side which runs from left to right 1/2 way up the wooden uprights obviously to stop them sagging in the middle. This beam is very thick in excess if 12" I guess so if I were to convert the attic it would intrude in the interior space.

Is it normal to leave these beams in or replace them with something thinner (steel?) I know the thickness of all the insulation etc will be quite thick but not sure if it will be as thick as the beam.

The house is a 1935 red brick victorian style affair.

[The Natural Philosopher]

Gable end rather than hipped?

Purlins?

What 'wooden uprights'?

Normally there are angled rafters and a ridge, and purlin half way along the rafters to stop them bowing laterally, not to support them.

If vertical support is required that's normally done by verticals to the ceiling joists, or W bracing from the rafter centers to the roof center line under the ridge.

In the absence of photos, get a structural engineer in. These sound MASSIVE for purlins. Something does not compute.

1935 was about 33 years after Victoria died. as it happens..if its 1935 they were NOT known for massive over-engineering, so something is going on here that needs more investigation.

Phone up local structural engineers and ask them to take a look, (report not needed less cost) - it's too much of a structural thing to make a guess on the Internet..and the implications of getting it badly wrong are expensive and dangerous.

[John Rumm]

You mean there is a gable end wall, and not a hipped roof by the sounds of it.

If by "uprights" you mean the slanted beams that run up the slope of the roof (usually known as rafters), then what you describe is a purlin. Its purpose is as you say to stop the rafters sagging under the weight of the tiles etc.

Depends on the exact position, and if you are having dwarf walls at the edges. The dwarf wall can replace the purlin in some cases. You may find they are behind where you want a wall anyway.

I had a purlin like this:

taken shortly before I took a chainsaw to the whole rear roof section ;-)

At the front there was a matching one. This was replaced with a swarf wall that intercepted the rafters a few inches lower:

is load bearing and transfers the roof load to the new strengthened floor.

[manatbandq]

It has a gable rather than a hipped roof. Nothing to do with it's attachment, or otherwise.

MBQ

[The Natural Philosopher]

It is not that effective at that. I thought the real problem was that the rafters, under compession, would suffer Euler collapse. The purlin stops that neatly. As indeed does nailing battens across them. Or indeed a sheet of ply over the whole of the rafters :-)

Thats the spirit!

I THINK you mean a DWARF wall ?

And is very nicely done if I may say so, and ideal for a loft conversion anyway.

[John Rumm]

Well, I should add that it does not achieve this on its own, it in turn needs supporting by something. In the style of property described this is usually by struts from the mid section of the purlin, at an angle down to a plate over the centre spine wall of the property. The lateral thrust of the strut being counterbalanced by that of the opposing member for the other side of the roof.

These struts and the purlin do prevent sagging of the rafters by quite a significant amount though. When I did my roof, having partially de-tiled the rear section of roof that was to be removed, we took out the purlin strut. The centre span of the rafters immediately fell by over 4" - and that was without the full weight of tiles on.

Was fun that bit... ten mins work, a whole world of space appeared that had been just waiting to be set free!

;-) Yup, I expect a swarf one could prove quite feeble!

Ta. Seems to be holding so far at least! ;-)

[Lobster]

So you didn't feel even the *slightest* hint of trepidation as you started cutting...?!

David

[John Rumm]

Only in the sense I remember thinking, I wish I had a pair of ballistic nylon trousers!