Stop me before I wreck my old wall...

[MdB]

I just started work on my dinning room and have just moved out of my comfort zone and could do with a few people confirming that I am doing the right thing.

The end wall of the room dates from 1870 and is stone rubble construction. It suffers from damp and I have identified the following as being possible reasons:

1) The outside ground level is above floor level in places and is boggy. This I plan to deal with ASAP (like tomorrow).

2) The outside of the wall has been repointed in cement.

3) The wall has had multiple layers of paint put onto it which is peeling away from the wall in places. i.e. it lets rain in but not out.

4) The floor inside is solid concrete. (with the odd crack in it)

With all the above, it is not too surprising that I am having problems internally. However, today's job was to investigate the inside wall and especially the alcove to the right of the fireplace.

The inside of the alcove is rendered in a soft grey substance which was very soft and you could easily push a thumbnail into it. This layer was soft, damp, cracked, sounded hollow and I damaged it a bit whilst removing the cupboard doors that originally enclosed the alcove. For this reason I thought it best to remove this layer, to find out what was underneath and so a better surface could be put on later.

The top layer is between 5mm and 25mm thick and is soft enough to push a screwdriver in easily as shown. It appears to be made from porridge as far as I can make out - its not something I have come across before.

The layer beneath it is a black tar like layer which I assume was put on due to previous damp problems. It obviously hasn't worked.

Beneath that is a layer of yellow paint and beneath that is a cement skim of between 5 and 20mm thick. It has lost all structural strength and fell out without hardly any encouragement.

Finally, below the cement is the original wall. It appears to be in a fair condition with my inexpert eye. The mortar around the stone is soft and clay like, I assume this is lime mortar and is soft because it is damp and will harden as it dries or could this really just be clay?

The plan is to remove all the junk that is currently on the wall and bare it back to the stone + mortar. The will then be covered in a lime plaster + lime wash. If I continue to suffer from damp after fixing the outside problems then I will consider dry lining (with ventilation) but that is way into the future.

I've stopped now as I am unsure if my plan is a good one. Am I doing the right thing?

 

[biffvernon]

Porridge? Mmmm.

Sounds like the right plan to me.

 

[Lime]

Porridge? Mmmm.

I like mine covered in brown sugar. Mmmmmmm

Sounds like the right plan to me.

I agree.

The most important is to get the outside ground level down, well down, if you can.
Try to lower the water level/table too if it is possible.
Have you any idea where the water is coming from?

 

[BMcD]

All of the above.

But as for the porridge it looks to me like Thistle Bonding a light weight gypsum plaster for low suction backgrounds and was I suspect used because the tar/bitumin applied as a waterproof barrier would have killed any suction.
Thistle bonding as with most gypsum plasters break down in damp conditions, becoming soft and crumbly

 

[MdB]

Have you any idea where the water is coming from?

I may have to ask Penners to help me there (just joking Penners ) see here.

The water level around the house is fairly high. We have a stream running near to the house and most of the ground around is boggy. We have been told that the previous owner put lots of drainage in so the garden isn't too bad. However, the ground was built up beside the house to help it drain away I suppose. Doesn't help with damp inside of the house though.

I'll start digging it out tomorrow (will be a fun job as its full of stinging nettles) and I'll see if I can find a better way to get the water to run away. Will have to speak to the neighbours though as it will potentially need to drain across their land.

I'm thinking that a french drain might be the best solution for outside.

Thanks for the comments on the work on the inside. Gives me more confidence to proceed.

 

[MdB]

But as for the porridge it looks to me like Thistle Bonding a light weight gypsum plaster

That sounds like it might be it as its very light weight.

 

[NT]

Could draining the ground cause structural movement?

NT

 

[worms]

I like mine covered in brown sugar.

For an authentic period approach please replace with salt!

will be a fun job as its full of stinging nettles

In November? That shows the difference that 600 miles of latitude make, my nettles are long gone!

 

[Penners]

I may have to ask Penners to help me there

Oh, I see. One minute you're describing divining as bunk, the next minute you want help from my mystical rods. :wink:

In your shoes, MdB, the soil level outside would be my first priority. Then getting rid of all the cr@p coating your walls, to let them dry out.

 

[MdB]

In your shoes, MdB, the soil level outside would be my first priority. Then getting rid of all the cr@p coating your walls, to let them dry out.

Thanks Penners, that's just what I spent today doing.

I've dropped the level outside by around 300mm after battling with the nettles with the strimmer. The soil was full of sand so was easy to dig though hard work to shift in the barrow.

The bonus was I came down onto an old brick floor which according to my neighbour is the floor from a stable block that used to be fixed onto one end of the house. Rather exciting to find that. Its not very large or in very great nick but it was good to find.

The bad news is the area I have dug out is surrounded on most sides by a high wall and I think I might have just dug myself a small swimming pool as it doesn't have an obvious drainage route. Its no worse than what was there before but I will keep an eye on it the next time it rains. I believe it will drain under the walls as the soil is so sandy.

I've also removed the porridge from the alcove inside the house and most of the cement render. Unfortunately (as always seems to be the case in these things) the first 80% came off quickly without problem. The last 20% of course is well stuck and its taking me a little while to get it off without damaging the wall too much.

The mortar (if you can call it that) is just clay or subsoil and is rather crumbly in places. The rock is mainly some sort of fairly crumbly sandstone though there are some other types and the odd lump of wood. No solid Cornish granite here. Hopefully a bit of lime mortar will fill in the gaps and firm it up a little. I guess I need to read up on how to do this.

Could draining the ground cause structural movement?

Half the wall already had the ground level at the level I was going down to so I wasn't too worried about undermining it. Now that I have found the old floor I've basically just returning it to the way it used to be so hopefully movement won't be a problem.

Inside I'm a bit worried about the dirt mortar drying out causing the wall to lose strength. However, there seems to be a lot of stone in the wall so I don't see it being to much of a problem. I have thought about switching the radiator off in the room so it doesn't dry out too quickly.

Thanks again for all the comments on what I'm doing.

 

[NT]

If your soil is very sandy it might not need any added drainage.


Maybe someone with more experience with this can clarify, but I gather there is an issuem you ought to be aware of. Earth based building material can lose strength badly when too wet, and rarely cement render can be the only thing holding up whats left. If it were mnine I'd be drying that clay mortar wall out quickly, and probably leave the remaining render alone until what is uncovered has dried to a reasonable extent.


>> Could draining the ground cause structural movement?[/quote]

> Half the wall already had the ground level at the level I was going down to so I wasn't too worried about undermining it. Now that I have found the old floor I've basically just returning it to the way it used to be so hopefully movement won't be a problem.

The issue I had in mind was not undermining but soil shrinkage due to changing water content. But if it sandy soil rather than clay this would not be likely.


> Inside I'm a bit worried about the dirt mortar drying out causing the wall to lose strength.

Its the other way round.


NT

 

[biffvernon]

Yes, earth mortars usually get stronger as they dry out.

 

[andrew gayton]

if a stable range pre-existed, be mindful of the potential for increased salts in the stone walling; i would use a limewash as a sacrificaila poultice on the wall before plastering so as to draw out as much salt as possible. had you thought of drylining with lath and lime plaster to leave an airgap?

 

[Lime]

The fact that the soil is very sandy would normally mean good drainage however in this situation, next to a stream, it is often the opposite.
Water collected in the sandy soil is feeding the stream and flows via your house's soil which means it will always be quite damp dependant on local rainfall.
Any large and continuous obstruction like a garden wall is not going to help the drainage.
However a house wall with no soil next to it but with occasional ponding is better than wet or damp sand all year long.
Time will tell.
At least it allows the wall to drain dry for some of the time.

 

[andrew gayton]

sp is supposed to be 'sacrificial'.................