Damp work Essex

[frogman]

I have some damp mainly on one internal wall, i suspect I need a french drain installed but would like someone who knows what they are doing to have a look and quote on work. The damp is on an internal gable end wall and floor. The wall I believe is lathe and plaster and the floor is very old concrete with a 5 year old screed over the top which I dont think helps. Externally the ground level is a few inches higher but there is also an aco drain which I dont thik paticularly helps .

Anyone know of a reliable company I can use for a quote?
Oh the house is circa 1700 no dpc that I know of.

 

[Flyfisher]

I'd suspect the high external ground level and the concrete floor as the main culprits. The concrete floor will be impermeable to damp, trapping it and effectively guiding it towards the walls where the high external ground level will prevent evaporation of the moisture until it's above the floor level.

A French drain won't do any harm and might help a little, but lowering the external ground level is likely to be more successful. If this is not possible then digging a small 'moat' along the affected wall and, if necessary, building a small retaining wall for the ground would expose the bottom of the wall to the outside air and facilitate good ventilation and thus evaporation. Don't full the trench with gravel as this will seriously impede ventilation. If you don't want an open trench it can be covered with some form of grating.

In extreme cases, I've known people dig up their concrete floor and replace it with a limecrete, which is still a solid floor but it is breathable and will allow damp from the ground to evaporate. Again, breathability and ventilation is really important for old buildings and they rarely respond well to modern materials and methods.

If you do get a company to come out to have a look, be careful to check they are experienced with old buildings. If they start taking about tanking or injected damp-proofing then beware.

There is a lot of info out there and it's well worth a bit of research before rising in with something that might make no difference or even make things worse. I'd suggest starting with the SPAB website. They have lots of good information.

One more thing - if the building is listed then consider contacting your local council 'historic buildings officer' for advice, which should be free.


Edit - just noticed the comment about a drain near the wall. I'd want to be completely sure this is working properly and is not damaged or leaking at the joints, which is not unusual especially with old 'salt glaze' drains.

 

[frogman]

Thanks, i basically came to the same conclusions as you have just mentioned. I don't own the external ground it is owned by a neighbour but im sure they would allow some work to be done.

As you say I need someone knowledgeable with historic buildings not your usual damp contractor injecting etc. Was hoping that someone may have a recommedation.

 

[MatthewC]

I support everything FF says, especially

lowering the external ground level is likely to be more successful.

I doubt you will find the sort of contractor you envisage. I did a lot of ground lowering on my house; even where I used a ground work contractor (we removed tons), I had to tell him what I wanted. It was so successful that my neighbour copied it, with similar results.

I suggest that you (yourself?) do just the ground lowering and checking the drain, then let it be until next summer when you might see some improvement. These things take time. However, I hope your user name is not indicative of the scale of the problem!

the house is circa 1700 no dpc that I know of.

For that you should be thankful!

 

[plasticpigeon]

the house is circa 1700 no dpc that I know of.

For that you should be thankful!

Really! I'd much rather have a house with a dpc. With no dpc wall and even floor finishes are far more critical.

 

[MikeG]

Essex is a big county. If you are in northern or eastern Essex I know a number of builders who would resolve these issues for you, but not if you are in southern or western parts of the county. Don't get a specialist "damp" contractor in, get a decent experienced local builder.

 

[frogman]

Thank you everyone for your replies.

This is not something I could do myself it's way beyond my limited DIY/bodging skills! Im just outside Chelmsford so fairly central Essex. MikeG can you give me the details of your builders? I have found a few local ones online who claim to specialise in old buildings but still unsure.

Thanks

 

[MikeG]

......Im just outside Chelmsford so fairly central Essex. MikeG can you give me the details of your builders?

I'd better check with them first to see if they're prepared to go as far as Chelmsford.

 

[MatthewC]

the house is circa 1700 no dpc that I know of.

For that you should be thankful!

Really! I'd much rather have a house with a dpc. With no dpc wall and even floor finishes are far more critical.

PP

In terms of modern DPCs and old buildings, I thought that this was a generally agreed statement (on this forum) and I stand by it, especially in relation to a C17 house. An original slate DPC is a good thing, but a chemical DPC can have a dreadful effect on a stone building, especially limestone - at best you just waste your money, at worst you can actually damage the stone permanently. A DPC of any sort is simply one way of tackling the symptoms of damp issues, and I maintain that fixing the real cause (such as high external ground levels or concrete up to the wall causing splashback) is a far more effective way of helping the building.

In my less knowledgeable days, I used some Thompson's Weatherseal (or similar) on the top part of an exterior wall monument at my old church in London. The whole thing was slowly deteriorating and I thought it wouldn't do any harm. Sadly, when I left four years later, the bit with the Weatherseal was eroding at a fast rate and was much worse than the rest of the monument. The guilty feeling is still with me!

Matthew

 

[plasticpigeon]

I have a slate DPC in my house. Far preferable to none at all. I would also much rather have a blue brick DPC than none at all. I wasn't taking abour an injected damp proof course, which I agree at best does nothing, and at worst when holes are drilled in the masonry causes terrible damage. I assumed frogman just meant that his house didn't have a damp proof course, which I really don't think is preferable to a proper damp proof course.

 

[Zebra]

I agree a proper damp proof course - a polythene layer between two courses of bricks - is good. I have installed one of these in my c1700 house. However, it was a last resort. Hopefully your case won't come to that, but if it did, lowering ground levels would have to be done first anyway, as you couldn't have a dpc installed with the ground breaching it. So do that first. Build a retaining wall and cover it with a grating. I can give you more details on the grating I used, and you can get advice on here about how deep to dig, that close to foundations.
Regarding choice of contractors, my advice would be to become your own expert, using this forum, and decide for yourself on the course of action, and then get someone to do that, rather than being advised by the contractors themselves. All contractors (and I am one myself although in a different field) will do what they know best - what they always do - not necessarily what is best for your house. I have said many times on here, even though nobody else particularly seems to espouse the view, that I have found younger contractors to be more biddable! I wanted strange weird things that nobody had ever heard of for my render, and found that younger guys (aged about 30) were up for giving it a go. I've found older contractors more likely to suck on their teeth and say "that wants cement that does." I apologise for my ageism, I only say it because I hope it might be helpful.

 

[Me!]

Anyone know of a reliable company I can use for a quote?

You could try this chap.

I have never had any contact with him personally, but he has been discussed on this site several times before and he seems to have the right approach. I believe he covers the whole country, but I'm not sure.

 

[frogman]

Thank you all for taking the time to reply.

Me! That is certainly an interesting site thanks.

Im not sure I can become an "expert" but I will try to learn as much I can!

I will add some pictures later, in the meantime what sort of depth and width should I be looking at when creating a gully, I cant lower the whole ground level as I do not own the land and it is actually part of a neighbours path. Also I should leave the gully empty rather than adding a French drain with a drainage pipe and filled with gravel?

 

[frogman]

Here is the outside:





The slate path is owned by my neighbour.


Inside:


Underneath the carpet the thin layer of concrete screed has blown. This was laid by the previous owner to level the floor. My original surveyor commented that that bits he could see underneath the screed were "possibly original but certainly very old"

 

[Zebra]

This thread has pictures of the gully I made.
http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=14035&p=192648&hilit=Gully#p192648

It is approximately 200mm internal width, which I guess your neighbour's slate path won't allow for as it currently is, unless they are amenable to making changes?

 

[frogman]

Thank you Zebra ill have a proper read through. Google research seems to say the gully should be 150mm below the DPC. As I dont have one om going to try 150mm below internl floor level does this seem ok? I have no idea how low the foundations are though. I will need to negotiate with the neighbour about cutting back his path. Hopefully he will allow it.

In your pics it looks like you have laid some gravel at the base is it bare soil underneath this?

 

[Zebra]

It is not filled with gravel - the angle from which the photo is taken is a little deceptive. It has gravel in the bottom (covering the drain which takes the water from the downpipes) but is open to the air. The difference between internal and external ground levels is some 400mm or so, therefore the gully is a little deeper than that.
150mm below internal floor level sounds good. If you get to the bottom of the footings - I don't mean foundations in the modern sense but a few wider courses below ground - then you can dig at 45 degrees from there in order not to undermine the footings.

 

[frogman]

Thank you Zebra,

I am making progress. We have a company to do a quote. They do work on churches and lots of historic buildings so hopefully will be a bit more knowledgeable than your average builder.

I found this sitehttps://blog.completepreservation.co.uk/2014/04/24/reducing-high-external-ground-levels/

Which has an example of basically exactly what I want I think. In this example they use a geotextile membrame of some sort to cover the bottom of the gully. Would you recommend this or should I just leave it as bare earth at the bottom?

 

[Zebra]

If one is building a French drain then I believe it is common practice to line the trench with a geotextile membrane to prevent worms from bringing the surrounding soil into the gravel filled trench. If the gully is open to the air, however, with a brick retaining wall holding the soil away, then I can't see the benefit of having a geotextile membrane in the bottom, though it would certainly do no harm.

 

[frogman]

Thanks zebra. Im a bit concerned that the soil could be washed away down the drain when it rains. If membrane will not effect evaporation from the soil I might add it anyway. Possibly at a later date.