Built late 19thC Dry rot / damp / Exterior ground height / Drainage

[bart]

Hi,

Avid reader becomes owner/poster thank you for taking the time to share in my learning.

We bought our dream late 19thC (fully renovated) 2 bed mid terrace property. 1 month on we have found 2 areas of damp, neither disclosed by the vendor or picked up by our full structural survey (but that's another story).

North west corner of circa 1950's kitchen extension we found black mould in kitchen cupboard.
North East corner of 19thC original building we found a mushroom.

On advice we called in Peter Cox (Rentokill) last week who discovered dry rot running along the kitchen skirting into the lounge and around the bathroom with elevated moisture readings of 30%+. Suggested remedial action includes removal of all effected timber, spray treatment, waterproof scree application, dpc injection and replaster. Total (ball park cost £4k) tbc in next weeks report.

However I was unnerved by the PC surveyors/salesman's apparent lack of knowledge when I quizzed him on where the water would go as a result of the intended waterproofing in the lounge and seemed disinterested in addressing the source of the damp.

Reading here and elsewhere it seems waterproofing/ dpc is a poor option even in the bathroom given a solid brick built construction and managing water source improving ventilation is more of the priority.

Positioned near the the top of a hill our 20m rear garden drops about 1.2m before the back door. The lounge is another 20mm step down internally -intended solution french drain (dependant on septic tank feeds) 40mm depth roughly 800mm from North wall running west-east to a run off in our neighbours garden.

We've additional discovered all downpipes aren't linked to surface water drainage - intended solution water butts or channel as above.

One of our downpipes appears to be cemented in right next to septic tank vent (which is a concern) and the exterior ground level raised (above the kitchen dpc) in the worst effected areas - intended solution investigate downpipe and lower ground levels and south-north French drain to feed west east drainage.

Additionally I have some concerns about septic tank centrally located upslope (levels look low and garden looks lush) and have a survey booked which I hope might provide insight before digging French drain.

Have I got my priorities right?
1. Investigate septic tank
2. Dig French drain/ drainage /connect water butts
3. Treat dry rot

As an aside removing some plaster we found some kind of plastic water proofing behind lime plaster in the lounge and found modern paint in the shed which looks to have been liberally applied internally and externally so looks like I might well be a regular here for the foreseeable future...

Thanks again for the info and letting me bounce ideas

 

[malcolm]

I would guess the high exterior ground levels will be much of the problem. Ideally you want the ground level outside to be a couple of bricks lower than inside and for the bricks to be exposed and pointed with lime. That lets any water coming up the wall evaporate away before it thinks about getting inside.

A French drain is good for surface water (until it gets blocked by soil) but will not allow evaporation from the wall and will be wet below the top layer of pebbles. An open trench would be a lot better: https://www.periodproperty.co.uk/forum/threads/the-zebcolm-trench.17575/

The masonry paint you have outside will be waterproof. That means no chance for water to evaporate away once it's in the wall so it is important to stop it from getting in.

Worthwhile sorting out rainwater drainage. If you hire a person with a digger a soakaway can be installed in a day.

I would forget damp firms as the problem should go away once you have sorted out the basics. For curiosity what is that wall in the third picture with damp all the way up?

Forgot to say - It's easy to spend money on experts when you first buy a house. It's lack of confidence and a familiarity with money spending during the buying process. It's your house and most stuff is simple. You can figure it out without experts.

 

[Lacan07]

For curiosity what is that wall in the third picture with damp all the way up?

That's the inside of his cupboard. I must admit I thought it was a wall at first lol.

 

[bart]

I would guess the high exterior ground levels will be much of the problem. Ideally you want the ground level outside to be a couple of bricks lower than inside and for the bricks to be exposed and pointed with lime. That lets any water coming up the wall evaporate away before it thinks about getting inside.

A French drain is good for surface water (until it gets blocked by soil) but will not allow evaporation from the wall and will be wet below the top layer of pebbles. An open trench would be a lot better: https://www.periodproperty.co.uk/forum/threads/the-zebcolm-trench.17575/

The masonry paint you have outside will be waterproof. That means no chance for water to evaporate away once it's in the wall so it is important to stop it from getting in.

Worthwhile sorting out rainwater drainage. If you hire a person with a digger a soakaway can be installed in a day.

I would forget damp firms as the problem should go away once you have sorted out the basics. For curiosity what is that wall in the third picture with damp all the way up?

Forgot to say - It's easy to spend money on experts when you first buy a house. It's lack of confidence and a familiarity with money spending during the buying process. It's your house and most stuff is simple. You can figure it out without experts.

Thanks Malcolm, re checking my post I spotted metric errors. Internal step is 200mm down to lounge from backdoor. Im intending digging 400mm trench. Hence concern re septic tank feeds from house.

Yes £210 to rentokill was a waste although I learned they can't be trusted. Septic tank empty and survey is £600 now possibly on the back-burner.

Reading your post the open trench looks great especially as its our backgarden so no cars likely. With a gradient to keep the majority of water along the wall away from the house (I'm presuming cement) it looks far more effective with ease of access for maintenance especially as I have 1.2m width available before first step up in garden...also exposed lime render house side could be good for any moisture that makes it past... turns out I'm building a moat just need a drawbridge... That said have you had any issues leaving foundations exposed? 45°from foundations is same as French drain although leaving foundations open to the air is a concern for some reason did you reinforce at all for lateral movement please?

Now thinking how the hell to remove cement/tiling mess without damaging septic tank drains (5th photo) and run along kitchen wall to run a moat all the way round.

P.s. 3rd photo is of under counter kitchen cabinet NW corner of kitchen cabinet. Havent removed the cupboard but dehumidifier has dried reasonably well in this weather so am hoping channelling that side down pipes combined with above will suffice.

Thanks again for your time I'll post my progress.

 

[Cubist]

A quick addition to the good advice already offered above. Oftentimes, when considering damp problems, our thoughts and remedies are focused on penetrating damp from below ground or through walls and we often overlook the damp we generate indoors through our day-to-day occupation and activities. Kitchens and bathrooms in particular can be a major source of moisture that can quickly be absorbed into surrounding materials and, over time, induce some of the problems you are seeing. In your shoes I would also give some consideration to the heating and ventilation systems to see if any improvements can be made there too.

 

[bart]

A quick addition to the good advice already offered above. Oftentimes, when considering damp problems, our thoughts and remedies are focused on penetrating damp from below ground or through walls and we often overlook the damp we generate indoors through our day-to-day occupation and activities. Kitchens and bathrooms in particular can be a major source of moisture that can quickly be absorbed into surrounding materials and, over time, induce some of the problems you are seeing. In your shoes I would also give some consideration to the heating and ventilation systems to see if any improvements can be made there too.

Thanks Cubist. Yes ventilation is an issue in our little money pit especially as I've now appreciated the whole house is suffocating in modern paint. Waiting with trepidation for winter to see how bad condensation gets.

The single asthmatic extractor fan doesn't seem sufficient in our bathroom and the 2 air bricks in the south facing wall of the lounge have been covered up by skirting board and are above the terracotta tiled/cement flooring (throughout ground floor).

The heating system has been modernised with radiators throughout which are present on every wall with even a modicum of damp issues as highlighted by my new beeping toy. Beginning to think taking the floor up and installing wet underfloor heating throughout ground floor might be the best option although this will have to wait until ground levels have been sorted. Possibly the subject of my next post as I've yet to determin the foundation depth so unsure how deep I can go to allow for anything other than a hobit to live here!

 

[Matt Green]

That's active dry rot- that's a rarity. It's fruiting though, so it isn't happy.

The downpipes are the cause of fresh water ingress that caused that outbreak. I would suggest piping the water away from the building by whatever means necessary with PVC pipework or whatever to stop that area getting much wetter. Remove the skirting boards and wire brush the mycelium off the walls: this will allow you to check for fresh growth and give you more indication of any water sources or embedded timbers that might not be obvious at the moment.

 

[bart]

That's active dry rot- that's a rarity. It's fruiting though, so it isn't happy.

The downpipes are the cause of fresh water ingress that caused that outbreak. I would suggest piping the water away from the building by whatever means necessary with PVC pipework or whatever to stop that area getting much wetter. Remove the skirting boards and wire brush the mycelium off the walls: this will allow you to check for fresh growth and give you more indication of any water sources or embedded timbers that might not be obvious at the moment.

Thanks Matt brilliant advice while waiting on groundworkers. Finding 30%+ in the brick work in the shared wall under the stairs has thankfully persuaded the neighbours to get on board that water butt.

I guess I should feel vindicated in some ways, my dry rot is fruiting. Understood re wire brushing - I've held off stripping the plaster and further exposing the walls to dry out until the water source is taken care of... ok so maybe I'm a little scared of what I'll find - time to watch that kettle I guess.

 

[noj]

One thought on water butts, it's a case not of getting water to them, but away, once they're full!

Once a butt/cistern/storage tank is full then it's as effective as a slab of concrete when there's any further rainfall.

 

[bart]

One thought on water butts, it's a case not of getting water to them, but away, once they're full!

Once a butt/cistern/storage tank is full then it's as effective as a slab of concrete when there's any further rainfall.

I hear you noj. Butts a very temporary measure whilst I'm waiting for digging out then I'm hoping they'll channel in my moat. Eventually hoping they'll provide additional water management upstream at the old pigsty and I can blame my green fingered wife.

 

[Cubist]

at the old pigsty and I can blame my green fingered wife.

Come on, that's not going to happen.... unless of course your'e planning to take up residence with them.

 

[bart]

Come on, that's not going to happen.... unless of course your'e planning to take up residence with them.

The way things have gone with our dream purchase you might be right.
At the moment the pigsty is described as secret and secure as its got our worldly nick nacks inside....habitable? another work in progress.

 

[bart]

That's active dry rot- that's a rarity. It's fruiting though, so it isn't happy.

The downpipes are the cause of fresh water ingress that caused that outbreak. I would suggest piping the water away from the building by whatever means necessary with PVC pipework or whatever to stop that area getting much wetter. Remove the skirting boards and wire brush the mycelium off the walls: this will allow you to check for fresh growth and give you more indication of any water sources or embedded timbers that might not be obvious at the moment.

Good news removing skirting reduced beeping readings from 30%+ to 10%.
Bad news removing the skirting boards in the other affected areas (I'm aware of so far) I think I found evidence of wood worm (Matt - please - would that be right?) and I think my dry rot is so wet its now exiting the building.

 

[Matt Green]

Fruiting on an outside surface makes sense for the fungus-it's trying to get rid of its spores. It looks pretty fluffy behind there- clean it up and you can start to see what is going on.

That insect damage is from wood-boring weevil (likely Euophryum species) that likes eating the early growth along the grain in softwoods in ground contact where it absorbs water. Chances are they were there before the fungus and they are not a problem in as much as if the timber is dry, those weevils will not attack it.

 

[bart]

Fruiting on an outside surface makes sense for the fungus-it's trying to get rid of its spores. It looks pretty fluffy behind there- clean it up and you can start to see what is going on.

That insect damage is from wood-boring weevil (likely Euophryum species) that likes eating the early growth along the grain in softwoods in ground contact where it absorbs water. Chances are they were there before the fungus and they are not a problem in as much as if the timber is dry, those weevils will not attack it.

Thanks for the good news. Unsure if I've cleaned up as intended.
1st 2 images looks like 2 minor faults to repair
image 3 damp around septic tank vent is a concern.

 

[bart]

Dry rot spread all the way up under the waterproofing someone put on.

Hoping now its gone with the skirting boards from lounge, bathroom and kitchen it'll slow things down a little and give me time to fix the guttering or would stripping the plaster now be an idea?

I have fans, oil heaters and dehumidifier all on duty with a 20 air cycle per hour extractor fan in the post.

 

[Cubist]

My money would go on addressing the water/moisture ingress problem first. And hope that some of the plaster inside comes down by itself in the meantime. Not much of a saving I know but 'every little helps'.

 

[ThornhillMike]

That's active dry rot- that's a rarity.

I feel blessed to be renovating such an apparently rarified establishment...

 

[malcolm]

Goodness. Rot in the ceiling will tend to be down to roof leakage.

I've not experienced anything that bad. My general philosophy for all things damp is if you can stop the damp from getting in and also let it out when it does get in there should be no problem. Worst I had was a kitchen with about 5 different ways water could get in and they had fixed it with tanking.

 

[ThornhillMike]

Goodness. Rot in the ceiling will tend to be down to roof leakage.

I've not experienced anything that bad. My general philosophy for all things damp is if you can stop the damp from getting in and also let it out when it does get in there should be no problem. Worst I had was a kitchen with about 5 different ways water could get in and they had fixed it with tanking.

Therein lies the root of our problems. The house was left unheated, unventilated and with a leaking roof for over three years (I suspect the roof for longer). The rot is in the first floor ceiling and the second floor above, and yes all down to a leaking box gutter. Roof all now sealed and the painful task of drying out begins. The only saving grace is that Manx Stone 'breathes', so should dry out as quickly as it became so wet. As Matt said, at least the rot is fruiting, meaning we're making progress (he says!).