Damp cottage, building control and insulation/concrete floor

[shooples]

Hello,

I've been browsing the forum for a while, absorbing all your tips, but now I need some advice and I hope you can help.

We bought a cottage (approx. 1780s with a weird 1989 flat roof extension) that has some sereious issues with penetrating damp due to general poor upkeep and modern non-breathable paint on the outside. We've removed the exterior paint and set about getting plans and permissions in place to make some changes to make the layout work better for a young family and to install oil central heating (currently it's only electric storage heaters and unfortunately renewable systems are not suitable).

Because of the damp the plaster is completely shot and needs replacing. Now our architect tells us that building control will insist that we put in 100mm celotex insulation. Aside from the impact on space, I have serious concerns about the suitability of this for an old property with a history of damp. Is there anything we can do?

We've also been told that the floor needs to be completely replaced with concrete. Here's what our architect said when I questioned that:

"Unfortunately, the existing floor is made up of 2 layers of tiles on ballast and not much else. When all the other elements of the house are upgraded and the heating is switched on, the floor will draw up a lot of moisture. Just because it hasn’t leaked yet does not mean to say it won’t leak in the future. Also your heating system will need to be designed with a higher load to take into account there is no insulation in the floor. This means the radiators will have to be bigger. I have confirmed with building control if you leave the floor exactly as it is then you may not need to upgrade it in terms of insulation. You would not be able to take the tiles off. You would need to apply some sort of waterproof membrane and put a floor finish over that. We would strongly recommend you replace the existing floor in order to prevent further costly repair works in the future."

I'm concerned that a concrete floor is also inappropriate for a property like this, and any sort of waterproof membrane might exacerbate damp problems, as previous modern 'solutions' did. Are my concerns well-founded? I have a couple of photos of the floor which I'll upload separately.

Any help would be greatly appreciated, I feel like we're being railroaded by our architect and I don't have the expertise to make the right decisions.

 

[MatthewC]

Hi shooples

I'll just bump this up as first posts tend to get lost for a while.

My answer is that you need to lay a (breathable) limecrete floor, not concrete. I've done one (see http://houseintheenchantedforest.blogspot.co.uk/2011/04/fitting-limecrete-floor-part-1.html) so I would say that, wouldn't I? People like Mike Wye or Ty Mawr can advise you on the construction and, possibly, tell you how to get Building Control to agree.

As for your architect, is he symapthetic and understanding about damp? A concrete floor will just drive damp to the walls and cause a different problem, as you suspect. In my case, the house is listed, and the BCO was very amenable and willing to learn from me (!) - is your house listed?

 

[Cottage cosy]

The start of your post read like you were talking about our cottage! we have the exact same issues and are steering well away from any cement, plastic paints etc for exactly the reason you are removing the external finishes at the moment, they cause damp!

so Just to second the above, limecrete and insulating lime moras/ board are undoubtably the way to go.
We have found ty mwar excellent for advice.

Sorry, no advice on building control.

 

[plasticpigeon]

Or just don't tell building control and get a new architect. Matthew, I do wonder how "breathable" a limecrete floor is, and how it can be quantified, and also what is the optimum amount of permeability.

With old houses, It puzzles me how a membrane can be properly inserted. My house for example has a slate damp proof course. How can a damp proof membrane be lapped into a slate damp proof course??? I bet most people just put the membrane down and pour in the concrete cutting the membrane flush with the concrete when it has set. Worse still on my road I see that most people have a raised kitchen floor meaning than the damp proof membrane and concrete were laid on top of the original floor. This means that the membrane buts up against the wall above the slate damp proof course. No wonder most old houses I see have some damp at the bottom of the walls.

 

[MatthewC]

Or just don't tell building control and get a new architect.

I thought that but didn't want to say it!

Matthew, I do wonder how "breathable" a limecrete floor is, and how it can be quantified, and also what is the optimum amount of permeability.

I can't answer the question with scientific facts and equations, but I can say that since my floor initially dried out, there has never been either sight or smell of dampness, so I'm totally convinced that it works. Of course, lowering the exterior ground along two sides of the room helped as well. Even though the other two walls have an old solid floor at the same floor level on the other side, there is still no dampness at the wall.

 

[Keithj]

I would question some of what your architect has been telling you. We've recently restored a Tudor house, and there were some major repairs made to the walls. At no stage was Celotex required.

Building Control wanted us to put 100mm Celotex in the roof when we replaced the tiles, but once they'd had a look they agreed that wasn't practicable. Common sense needs to come into the equation somewhere.

 

[Flyfisher]

Hello,
Any help would be greatly appreciated, I feel like we're being railroaded by our architect and I don't have the expertise to make the right decisions.

You probably don't have the required expertise (very few of us did when we started our period house journeys) but you're already doing exactly the right thing by questioning things you don't feel comfortable with and seeking as many other opinions as you can. Obviously we know nothing about your architect but it's possible that he doesn't have the required expertise with old buildings either.

I always like to question everything an 'expert' tells me. A real expert will delight in explaining the reasons behind their advice and it's a great way to learn. Any expert who becomes defensive when questioned or adopts a lofty 'because I say so' defence just sets off alarm bells in my head.

So, I would be asking your architect about the possible side effects of filling your old house with an impermeable slab of concrete and see what he says. I'd also ask about possbile alternatives, like limecrete for example, and again see what he says. I've no doubt you'll also be able to ask other relevant questions as well.