Sealing Concrete Guttering.

[joddle]

Having lived with the problems of having precast contrete gutters, some years ago I had them lined with an aluminium liner. At the same time I had the roof re-felted and rebattoned and all the tiles re-hung.

The improvement was dramatic and from having really wet interior walls the house was almost normal. However a few issues do remain. O some of the internal wall, at the height of the guttering, I do get mould on the inner walls and assume this is due to some moisture still getting through the joints by capilary action in the gutter sections to the inner cavity wall.

one thing occurs to me is that the aluminium section only fit over the side of the gutter a little way and therfore when the gutters get very full as in a flash downpour, water will overflow and end up running down the concrete sections which is why I think the damp can still get though. I have thought of extending the sides of the gettering with sheet aluminium so it forms a drip haning from under the existing gutters to a point an inch or so below the outside section of the concrete gutter hoping this will prevent water actually reachig the gutter secitons. I addition I want to paint the underside of the gutter sections with a ruberised paint to seal them , especially around the point where the sections meet the outer walls.

I have had the new gutter lining checked and there are no leaks and so
short of cutting off the gutters completely is there anything else I can do? Any ideas please?

 

[Mw Roofline]

EPDM works well with concrete gutters. We've just relined a row of 7 Terraced houses starting at the front edge of the gutter going a metre up the roof.

You could drop a swimming pool onto the gutters and it just won't leak.

You can get epdm dirt cheap here

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=170645402814&ssPageName=STRK:MESELX:IT

 

[Alastairreid]

Could be cold bridging from your gutters=condensation. possibly insulating the exterior wall will cure.

 

[joddle]

Thanks for the above posts - alas now I have had the alaminium guttering put in (several years ago) it will be impractical to overlay another membrane over the top - in addition I live in a semi and the guttering continues around my neighbours house as well so anything we do we do at the same time to ensure better integrity of the jobs.

I take note of the "cold" issue perhaps leading to damp and mould on the inner walls - seems a definate possibility especially as in parts of the house there are hairline cracks where the gutter blocks have settled over the years - it seems impossible to completely eradicate these without lifting the whole roof and replacing the gutters!!! - not a job I'm about to take on I hasten to add! As for external insulation - what can be added to facing brickwork? - and will cavity wall insulation help?

 

[Nige F]

Could be cold bridging from your gutters=condensation. possibly insulating the exterior wall will cure.

Seems to me this is most likely - Tho` I`m not familiar with the exact detailing of concrete Finlock gutters - maybe they cross the cavity in which case infill insulation will not help that particular problem - tho` it probably will make the house warmer overall - but there is debate on cav. wall insulation pros + cons too . Do you know a builder , or have a trusted one you have used before

 

[joddle]

I`m not familiar with the exact detailing of concrete Finlock gutters - maybe they cross the cavity in which case infill insulation will not help that particular problem

Yes the Finlock gutters do cross the cavity and form the top of the inside wall in the upstairs rooms albeit they are plastered. The problem is I think that with settlement they are no longer totally watertight - even if they were when installed. They have certainly settled over the years and in some places the outline of the gutter segments are seen as hairline cracks in the plaster on the inside.

In Spain wher I spend a lot of time, the exterior walls of many houses are painted with a product which appeares to have a ruberised content. Normally in dark red or white the product keeps walls and terraces watertight so I was wondering if applying this to the exterior parts of the gutter would help to seal the cracks - but I have no idea what it would be called in the UK - any ideas?

 

[Nige F]

I can see what you mean now . I would suggest something like Thompsons water seal , being a colourless liquid it will not alter the finish of the exposed concrete . It actually did a brilliant job on my chimney ( flaunching round the pot ) And is pretty good on concrete too. . Being as thin as water it will be possible to pour it into your gutter under the aluminium . Best to check out the manufacturers site and also if the smell of it is acceptable until it dries - you don`t want to fumigate the bedrooms I still go with the cold bridge as the most likely cause .

 

[freethinker]

Hi,
It would appear that the problem is caused by cold bridging. This is quite often exacerbated by retrospective cavity fill which polarises the cold spots caused by the concrete finlock gutters. Lining can never cure cold bridging, which is why it is usually better to remove the concrete gutters and insulate the outside face and replace with PVCue profiles to the fascia and soffit.
A solution may be to fit insulation (say 25mm PIR celotex etc) and box over it with plasterboard and coving (for aesthetics).