Cost of new purlin?

[Klang180]

Structural surveyor has said this needs replacing so looking to hear how much it would likely cost on this mid-terrace 1920s house in Exeter?

Surveyor's informal summary:

1. The purlin is a definite issue. The original purlin has split and deflected, and the splice strengthening is inadequate. It needs a new full length purlin installing + some cross collars and/or props.

 

[Harry Bloomfield]

The purlin is a definite issue. The original purlin has split and deflected, and the splice strengthening is inadequate. It needs a new full length purlin installing + some cross collars and/or props.

That strengthening splice, looks like some random piece of scrap timber has been used. Replacing the entire purlin would be an very expensive job, any reason why it could not be propped/jacked back to position, then steels added either side, through bolted?

 

[Klang180]

It does look shoddy doesn't it. I am not sure but the Strutural Surveyor thinks it must be replaced and I am no expert.

 

[noseall]

It does look shoddy doesn't it. I am not sure but the Strutural Surveyor thinks it must be replaced and I am no expert.

View attachment 341316

There are probably a few options, with all of them likely to require ceiling removal. A simple fix may be to (prop first) bolt a couple of pieces of sturdy angle steel, both sides of the purlin and bolt through. A local SE could advise.
The biggest headache is always access and getting lengthy items into place, especially where there are ceiling binders, cables, pipes, joists etc.

 

[cdbe]

Get your engineer to spec a flitch plate and feed it in via the eaves. Assuming the two ends bearing on the walls are ok it's going to be a lot easier to repair rather than replace.

 

[Klang180]

There are probably a few options, with all of them likely to require ceiling removal. A simple fix may be to (prop first) bolt a couple of pieces of sturdy angle steel, both sides of the purlin and bolt through. A local SE could advise.
The biggest headache is always access and getting lengthy items into place, especially where there are ceiling binders, cables, pipes, joists etc.

Thanks very much for this. Ceiling removal sounds very pricey indeed but the simple fix sounds slightly more manageable.

 

[Klang180]

Get your engineer to spec a flitch plate and feed it in via the eaves. Assuming the two ends bearing on the walls are ok it's going to be a lot easier to repair rather than replace.

Thanks for this. I have no idea what that is but will look it up as it sounds like a good plan. Cheers.

 

[Harry Bloomfield]

Thanks for this. I have no idea what that is but will look it up as it sounds like a good plan. Cheers.

It is the idea I suggested, in post #2 above.. Basically, it would involve jacking and supporting the purlin, back to where it should be, then some sheet steel panels, stretching well beyond either side of the damage, placed at each side of the timber, with threaded rod and nuts clamping through steels and timber.

That fix, is dependent on the timber ends being perfectly sound.

With a bit of luck, you should be able to pass the steel up via the loft hatch. To jack and support, you would need to first support the ceiling below, using planks and acros, plank across the loft floor, then finally jack up the purlin, gently, a little at a time, watching the progress carefully, until back to straight and level. Finally, you fit the steels, drill, and bolt the entire sandwich together tightly.

 

[^woody^]

Glue and screw some 12mm ply either side.

 

[Klang180]

It is the idea I suggested, in post #2 above.. Basically, it would involve jacking and supporting the purlin, back to where it should be, then some sheet steel panels, stretching well beyond either side of the damage, placed at each side of the timber, with threaded rod and nuts clamping through steels and timber.

That fix, is dependent on the timber ends being perfectly sound.

With a bit of luck, you should be able to pass the steel up via the loft hatch. To jack and support, you would need to first support the ceiling below, using planks and acros, plank across the loft floor, then finally jack up the purlin, gently, a little at a time, watching the progress carefully, until back to straight and level. Finally, you fit the steels, drill, and bolt the entire sandwich together tightly.

Thanks so much for that explanation, sounds like a very sensible approach to take. Will look into it further. Can't thank you enough.

 

[Klang180]

Just for anyone who is interested and might have a view below is the text in reference to this problem. If anyone can be bothered to read this and looking at the picture above and below do you think his comments make sense? He has put a lot in this report that may need addressing and by scrutinising this section of the report we may be able to assess the quality of those recommendations??

The main area of concern, forming the original scope of our brief, is in the roof space
where there is substantial deflection and splitting of the rear purlin, which has been
repaired to a poor standard. A bolted splice timber has been installed, although this is a
smaller section than the original member and there are only limited coach bolts into the
failed section. Also, unusually the purlins span across the full width of the building in
between the party walls, without any intermediate support via collars and/or props to
reduce the span. This matter needs to be addressed, although not urgently given that the
failure and remedial works must have been undertaken some years ago and also since the
weight of the original roof cladding has been reduced, associated with a change to
lightweight Eternit type slates.

3.9 Strengthening of the roof structure to ensure future stability might most practically be
achieved by installing new purlins to supplement the existing. This applies to the front
purlin also, as there is considered to be a risk of failure to this member also. However,
given the difficulties involved in installing long lengths of timber into a mid-terrace
property, the purlins may need to be installed in two shorter lengths, with joints to
correspond with the positioning of a new substantial central collar. It should also be
determined whether it would be feasible to install raking props from the new collar/purlin
junctions down on to the first floor cross wall, subject to a localised dimensional survey.

3.10 Although we have not within the scope of a visual Structural Engineer’s Report prepared
any calculations to determine the required sizes of any new roof timbers, we anticipate
that the purlins would need to be of the order of 225mm x 75mm, with a new collar
around 200mm x 63mm and, possibly, similar sized raking props, although no smaller
than 150mm x 63mm. If categorical advice is required, the sizes would need to be
confirmed by calculation and this would firstly involve a measured survey. All new
connections should be coach bolted and it is suggested that the Local Authority are
approached, as the works may require Building Regulation Approval. Also, given that it
will be necessary to embed the new purlins into the party walls, this will require the
consent of the adjoining owners, in accordance with the requirements of the Party Wall etc
2403-S-4441 - 13 -
Act 1996. Approval must be obtained before any works involving disturbance of the party
walls takes place.