Loft Conversion - What is this roof type?!

[Arnalt]

Hi everyone!

I am looking at converting my loft potentially by myself over a period of time, into a habitable space (with building regulations approval & structural engineer input, but without a dormer). I am at early stage and set the scene below:

I live in a 1963 semi detached house - I believe it was completed in 1963 but they may have started building late '50s... Previous owner had done an attempted partial conversion which I have now removed (was just boarded over the existing ceiling joists which are 4"x1.5" and had a makeshift wall etc). I have reinforced some joists through sistering C24 2x4s to existing ceiling joists (because the previous owner had severely weakened them through drilling holes etc...previous owner has done a variety of questionable DIY which has now been rectified by professional builders).

Existing Structure (seems to be a cross between a traditional roof and a TDA bolted truss roof):

- 2 Purlins which are set into the gable walls either end - seem to be 8x2s?
- 3 ceiling binders - 4x2s (2 directly underneath the purlins and one central down the middle of the loft). The two which are underneath the purlins are set into the wall on the external wall, but NOT on the party wall. (is this normal? I am a touch concerned) The central one is two pieces of timber lapped in the middle - both ends are set in the walls with some internal supporting walls underneath.
- There are two bolted trusses in the middle of the loft either side of the chimney stack which I would like removed and the roof restructured to take the load (seems to be a hybrid between a traditional roof and a modern roof). I wonder if anyone can tell me why these are here and why there are also vertical thin timbers attached? I suspect they might have been put in as additional support for the water tanks, which have since been removed due to installation of a combo boiler. Would love your input!
- Could a conversion be done either around these 'trusses' leaving current structure intact but remove the vertical hangers/struts and central ceiling binder?
- Also looking at partially (at roof/loft level) or fully remove the chimney stack and make right the hole in roof - what is required structurally.
- Also it looks like someone may have changed the roof structure which is concerning, as at the end where the binders are not built into the party wall, there are bricks filling in 2 old/previous holes which are a bit higher up. Suspect that the binders may have originally gone into these holes perhaps? I have begun to insulate the roof rafters by stapling foil insulation over them (have kept 50mm gap minimum from felt and repaired felt where it had holes).
- There is also already a window in the loft at the gable end which was there when we purchased the house.

I've got some pictures, but would be great if anyone could tell me how straight forward a job this might be, as I would like to keep the budget as tight as possible doing a lot of the work myself! Also if anyone has come across a roof structure like this before? I've trawled the internet but been unable to find a roof exactly the same as mine! Have attached some pictures and appreciate your input.

 

[Arnalt]

I forgot to mention the current ceiling joists hung from the binders are 4"x1.5".

 

[theprinceofdarkness]

Long purlins are braced with a prop which sits over an internal wall, so they are normally every 16' or so (very variable!). In Pic 3 there is silver foil over a purlin with a neat bit missing, this could be where the prop was, does this line up with an internal wall? Also in this pic, just beyond the end of the trap, there is a thin piece of wood with another piece siting on it. This piece is too thin to carry any weight, so the bit standing on it can not be carrying any weight.
Frank

 

[bernardgreen]

I would hazard a guess that that roof originally had horizontal beams from purlin to purlin and someone removed them. Possibly to open up the space to use as a room.

Then the rafters started sagging and those double struts were fitted to prevent ( reduce ) the amount of sag in the rafters.

 

[KenGMac]

Arnalt, hi

This loft space appears to have been shall we say, knocked about a bit?

My initial reaction would be to employ the services of a good competent Structural Engineer, soon to get ideas on procedures.

Because of the previous "work" within this loft space, you need to be certain as to what is needed and what must not be cut / altered / adapted Etc.

Ken.

 

[Arnalt]

Thanks everyone. In picture 3 the thin piece of wood with another thin piece on top of it is not actually part of the structure (sorry I should have removed that from the photo!) It's a part of the rather makeshift 'stud' wall the previous person had made. I've removed that now. The neat piece of foil is something that I did to try to insulate the loft better, so I don't think this is where a prop might have been? There is a supporting internal wall that runs right next to the chimney stack and also up from the hallway and into the small box room at the front of the house. The two 'trusses' in my picture are not actually above any kind of supporting wall at all which makes me question what exactly they are doing! Is the general consensus that this is a traditional cut loft and not a truss/modern loft? I am hoping that will make it easier/cheaper to a) rectify b) convert!

 

[Arnalt]

A few more photos!

 

[bernardgreen]

My initial reaction would be to employ the services of a good competent Structural Engineer, soon to get ideas on procedures

I totally agree with that advice. That roof structure needs to be professionally checked before any work is done in there.

Bricks filling gaps in the original block work wall. What was there befroe the bricks ? Possibly beams that were part of the original roof structure.