2 Jan 2021
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United Kingdom
Hi everyone

we recently purchased our first home - a lovely three bed Edwardian semi in need of some work.

I am looking for some advice on mould.

we have noticed a few areas of damp.

1) The interior outside wall in the kitchen. There is no extractor fan, no heating and a poorly fitted back door. Brickwork on the exterior also needs repointing. Plaster has bubbled from around the skirting in certain places and up to the window sill in certain locations. We have also noticed bumps in the flooring where it is raised in certain places. Believe vinyl has been stuck on plywood on top of suspended timber.

2) Inside the old chimney breast in the dining room black mould is growing. Again it is an outside wall. Outside again needs repointing however it is protected from rainwater somewhat by a small shed like side return for bikes etc. We also need to repoint the chimney and look at leading as looks like this needs sorting.

3) in the lounge (directly next to dining room) the alcove next to the fireplace in here is showing black mould. This is in the cupboard. Black mould on skirting and then ever so slightly higher. Again, outside wall with the side return adjoined on the exterior.

4) we lifted one of the original floorboards in the dining room and whilst the joists look okay as far as we can tell, there looks to be a white/ orange tinged mould growing on the subfloor. This is not growing on the wood as far as we can tell.

we are concerned about damp and whether this sounds like penetrative, rising or condensation. Want to make sure we treat it all properly and know damp specialists will just try and sell us expensive DPC. Want to make sure timber etc is all sound and not get conned into something that won’t actually help!

pictures attached. I cleaned the lounge and dining room fire place but they did look much worse than this before.

thanks in advance for your help!


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The interior outside wall in the kitchen. There is no extractor fan, no heating and a poorly fitted back door.

So fit an extractor. Over the cooker, and vented straight through the external wall, will be most effective because it will draw out cooking steam and odours straight away. If you get a wall fan, it will need to be more powerful to have the same effect. It should be fitted as close to the ceiling, and as far from the door, as possible.

Plaster has bubbled from around the skirting in certain places and up to the window sill in certain locations. We have also noticed bumps in the flooring where it is raised in certain places. Believe vinyl has been stuck on plywood on top of suspended timber.
this suggests damp from the floor. Are you sure it is not a solid (concrete) floor?

Look for air vents. How many are there. Are they blocked. has the external ground/paving level been raised since the house was built. Do puddles lie against the house. Are there signs or cracked, broken sunken or repaired concrete or ground round the gulleys and downpipes. You can expect all the gullies and drain junctions to be brown clay, and to be cracked and leaking for the last 80 years if you are in a city, town, or near a major railway junction, airfield, factory, industrial area or harbour.

Believe vinyl has been stuck on plywood on top of suspended timber.

peel it up and have a look. Hardboard is often laid under vinyl to cover up unevenness or cracks, and it swells when damp (before it falls apart and rots)
Want to make sure we treat it all properly and know damp specialists will just try and sell us expensive DPC.

do not invite anyone into your home who sells chemical injections. They will try to sell you chemical injections. Damp is most often caused by poor ventilation; plumbing and drainage leaks, or building defects.

Chemical injections repair none of these.
Thank you John.

I am most concerned about the subfloor and the mould that seems to be growing there as think the other areas could be symptoms of the problem below ground.

Would you recommend a damp and timber surveyor instead of a damp specialist?

thanks for your help.
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look at the sources I mentioned. Broken drains, raised paving, blocked airbricks for a start.

A builder can do most of them. As around for local recommendations from neighbours or tradesmen you know and trust. Avoid advertising websites where people pay to be listed and have control over negative reviews.

a house of that age probably has leaking water pipes, commonly in the floor under the kitchen.

Is there a water meter and/or an external stopcock?
Get a survey by a building surveyor, or a specialist damp surveyor who does not work for a firm offering remedial damp work.

You have several issues there, which may be combining or individually contributing to overall damp related problems.
Thanks both. We will get someone in to have a look.

we have plenty of air vents and the floor outside is an adequate distance from the vent.

lifted up vinyl (see pic) and the kitchen floor is definitely damp underneath - you can smell it when you lift it, which you couldn’t before. Guess we won’t get an idea of how bad it is until we get someone in to lift the plywood and go beneath. Hopefully not dreaded dry rot!!!


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To me it actually all looks ok. Some damp/mould on the interior side of a cold outside wall (esp if there's no cavity) is fairly normal (condensation), and can lead to the bubbling plaster effect you are seeing. Any closed cupboard or unventilated space will suffer similarly. The underfloor looks pretty good to me. The timber is sound, the sleeper walls and bearers look good. I don't think the yellowish stuff on the ground is a concern. A bit of mould on the underside of the kitchen vinyl is also pretty normal.
As above, a good general builder should spot anything to be alarmed about pretty quickly.
Thanks. What do you reckon the yellowish stuff on the ground is? We assumed the worst but hopefully wrong! The joists do look okay from what we can see, which is good.
We're living in a 1902 semi which we have bare brick restored. Do you have cavity walls or solid? Is it brick outside or render? If brick you can tell if you have a cavity from the brick bond - solid will have rows of "half bricks" where the brickas are laid across the wall. If it does have a cavity will prob have airbricks into the cavity . IMHO this is crucial to know because it influences your options for insulation.
Cavity brick walls. Survey said no insulation had been added to cavity walls, which am glad about as have heard that in itself can cause problems. We have five air bricks in the property which I’ve made sure to clean of dust and spiders webs etc.

the exterior certainly needs work with repointing, guttering, chimney etc, which we knew before purchase and have budgeted for. What we’re trying to work out is whether this will solve issues with damp in kitchen, lounge and dining room or if this looks like a different issue entirely. We plan to redo the kitchen anyway so should be able to ascertain more for that room then, but hoping the lounge and dining room is issues with condensation on back wall/ exterior brickwork as opposed to rising damp or rot
Good news it's a cavity. IMHO do NOT get cavity wall insulation. The cavity will be quite small,and the ventilation will help to keep it dry. Our house was dripping wet when we inherited it - and it was all condensation and salts caused by 100 years of coal fires. We have gutted ours back to mostly bare brick - the plaster was falling off anyway, and we also removed all the lath and plaster ceilings except one room where we kept the cornice. Not saying you need to do this, but if the plaster is hollow and loose you have little choice.

IMHO trying to have modern living in an old house with cold walls invites condensation, especially as we try to eliminate draughts and natural ventilation.

We used insulated Plasterboard on every external wall with 60mm insulation where we could, and 25mm where we couldn't. The plaster itself was around 25mm thick so when removed gained us a little space. We discussed this plan with our BCO as wanted to know his opinion on risk of interstitial condensation, and we agreed as we had a ventilated cavity this was a good plan.

It did help that we had to replace all skirts and architraves anyway because of endemic woodworm. (and stairs and almost all floorboards)

It has turned out well - Two winters later and no sign of condensation and the house is toasty.

My own opinion is that unless you have actual leaks, any damp problem can be controlled through ventilation and insulation - no damp treatment required.
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Oh very jealous of your nice toasty house!!

luckily plaster all in tact etc, just little bit of damp on outside walls towards the bottom. Hopefully fixable through repointing and chimney work. Not going to strip all back
Wouldn't strip back unless you have to!, however when you come to decorate each room,it would be worth considering insulating the ext walls as you go.

If you have cavities, I believe that damp towards the bottom of outside walls will almost certainly be condensation. No harm in sorting the pointing, but I expect it won't be the cause or the cure. Def sort the chimney out, and cap any unused flues with vented caps, and any occasionally used flues with cowls to stop rain going down.

The other cause of "damp" is a lot of salts in the walls from years of coal fires. The salts are hygroscopic and hence attract moisture out the air.

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