Sagging Finlock (concrete) gutters - fixable?

[Alec Waters]

Hi all,

I have Finlock gutters at my house (this kind:

and they're sagging over the windows. This movement of the blocks has caused damage to both the plaster on the inside walls, and the rendering outside. There's almost certainly water damage to the brickwork between the two :(

How easy is this to fix? I'm not proposing that I do it myself, I just want to get some idea of the magnitude of the task.

Has anyone had this repair carried out in the past?

thanks, alec

[Peter Taylor]

Alec wrote

Hi Alec. It's a fairly major problem I'm afraid. Finlock gutters were a "good idea at the time" in the 50s and early 60s. The concrete gutter sections were laid directly on the top of the cavity external wall to form a continuous combined precast concrete gutter/fascia/wall plate and, where passing over window openings, the "lintel trough" was filled with concrete with a couple of steel reinforcing bars to make a beam. The water trough part was sealed with aluminium foil and bitumen. The trouble is that even tiny amounts of movement (due to thermal expansion, shrinkage or minor settlement/subsidence/heave) cause cracking and open joints and then the gutter starts to leak. For many years Finlock offered a fairly cheap relining service, but a better and more effective way of sealing them these days is to provide a separate rigid sheet aluminium liner which is unaffected by movement. As for the sagging, this is quite unusual and I can't say why it has happened in your case - sounds like there may be a problem with the reinforcement. One thing's for sure - it's not a simple repair.

If you can live with the sagging then it might be worthwhile just providing new aluminium liners (e.g.

but otherwise it really is not worth rebuilding the sagging sections. Even after you've done it and had the gutter relined to stop the leaks, there will still be a serious cold bridge situation and virtually always this causes severe condensation problems. The extra cost involved in removing the Finlock sections altogether is much more worthwhile IMO, although if your house is a semi that might be a problem unless your neighbour does it as well.

You will need to remove some of the roof tiling and support the wall plate under the rafters before you can do anything about the sagging lintels. If you rebuild them and form new beams you will probably need to remove the windows. Alternatively you could remove all the Finlock sections altogether, build up the cavity wall to plate level with bricks and blocks, and provide new steel lintels over the windows. You will need to extend all the rafter feet and provide a new fascia, soffit and gutter, and also plaster and decorate all the tops of the walls internally. It's also a good opportunity to sort out cavity wall and roof insulation.

I would suggest you get a few quotes from builders. Ideally give them a short specification or schedule of all the work required - this will make sure they all price on the same basis and prevent any nasty "extras" later.

Sorry to be the bearer of bad news. Good luck with it. Peter

[Alec Waters]

Hi Peter,

Thanks for the reply!

Here's what the Finlock people said on the matter:

I don't really know what these entail (I mean I can sort-of "guess", but I don't "know" if you see what I mean.). They both sound pretty major though.

alec

[Peter Taylor]

Alec Waters wrote

Well, that makes sense - never seen it myself though. Just goes to show how much of an expert I am then, doesn't it? :o)

I don't understand the bit about cantilever effect. As far as I can tell, this method involves only supporting the inner edge over the window opening. The outer edge (the gutter) and the roof load is still not properly supported.

I think they must mean Strongboy prop heads.

This is exactly what I envisaged.

As I said, a separate aluminium liner would be better.

Method 1 sounds like a bodge structurally, unless I'm missing something. It will still be quite expensive (guess about £2.5 - £3K for a semi + the gutter lining). Method 2 is better but involves an extensive amount of work and disruption, involving removal of windows. In both cases you'll still end up with a major cold bridge with a high possibility of damage to decorations and plaster due to condensation or gutter leaks.

Personally, I don't think Method 2 is worthwhile. If at all possible I would recommend you go the whole hog and remove the Finlock stuff altogether and put in a proper fascia and gutter. Ask around and get yourself a good builder and see what he has to say Alec, and then if necessary come back here.

One last point - were the windows replaced with uPVC prior to this damage occurring? If so, maybe the window company should have recognised the need to support the Finlock before they removed the old windows.

good luck Peter