Insulating Floors

[jsmac]

Hi again PPUKers,

Pulling up the linoleum floor in the kitchen of our house has revealed concrete underneath. Similarly, the dining room has floorboards laid directly on top of concrete. The kitchen and dining room are extensions that we think were done in the mid to late 19th century and are the only rooms in the house that are actually at the same level as the ground outside. They are also the coldest rooms in the house.

Since we have to rewire the house and install central heating I am wondering what our options are to insulate the floors of these rooms. We are planning on tiling the kitchen before it is refitted and using the floorboards that are currently in the dining room since they've been covered in carpet for decades and are in reasonably good condition.

Any advice and recommendations would be most welcome.

Thank you.

Scott

 

[paulc]

Facing a similar problem in as much as "how to insulate the ground floor". My floors are tongue & groove with one small area of concrete. Lifting the boards is not an option in most areas, and there is insufficient access underneath to go crawling around. On the basis that something is better than nothing, I put down a layer of aluminium foil followed by a layer of 5mm thick wood fibre boards. In the lounge, I've fitted 11mm thick underlay topped with a fairly deep pile carpet.

When it comes to doing the kitchen (half concrete, half suspended timber), it will be two layers of fibre boards finished off with a vinyl flooring. Lifting the timber floor is an option as it is chipboard as I recall - In which case, 25-50mm of Celotex could be inserted.

You say your floorboards are laid directly on top of concrete - Is there not any supporting joists to give an air gap ?

If there is no space between the concrete and floorboards, then your options for insulating are limited to:

• Digging out the concrete and installing a new floor from foundations up.
• A thin layer of something on top of the existing floor (wood fibre such as I have done)

 

[tobydog]

Whilst we have very nice under-floor heating in the new extension, the main part of the house (1640's) is concrete flooring from when it was 'renovated' in the 90's . We should be grateful, however, that the builder put down a layer of polystyrene, topped off with hefty plywood in the lounge at least. When we moved into the house in 2009 we still found the lounge floor too cold so we too used extra thick underlay. It did make some difference.

The problem for you is that, to make any real difference, insulation is going to raise overall floor levels to the point where you will have to adjust all your skirting boards and doors. You might also find that your kitchen units are then too low.

As Paul said, options are somewhat limited.

 

[jsmac]

Thank you both for your replies.

Paulc - yes, the floorboards are laid directly on top of the concrete in the dining room. In fact in some places it looks as though the boards have been laid IN the concrete so getting them up is going to be a struggle. Suffice to say that the work that was done, whenever it was done, is of a rather poor standard.

We're planning on completely gutting the very old and utilitarian kitchen and starting from scratch. So raising the floors a bit in order to allow for some layers of insulation is something we are considering. The concrete in the kitchen is not quite level and raised in the corners so we would have to contend with that, but the ceilings are nearly 3 meters high so we don't need to worry about the ceiling height. However, the door frames into the kitchen and dining room are only 1.8 m high so bruised foreheads is a concern.

Is digging out the concrete a viable option? Has anyone ever undertaken such a job and what would be the first steps to ascertaining how deep the concrete is? Or is it more straighforward to raise the heights of a couple of door frames after raising the floor?

Cheers,

Scott

 

[paulc]

A neighbour recently extended his 1950s build bungalow and dug out the solid concrete floor in the kitchen. It generated a substantial amount of waste material that was recycled as hardcore. Coupled with the underfloor heating, it made a big difference in keeping the place warm in his opinion.

As to whether it is a viable option for you, only you can decide. The first step would be to see how deep the foundations are by digging a couple of small test pits outside. The depth of the foundations will determine how far down you can excavate internally. A core sample from the concrete floor inside will reveal how much concrete needs to be broken up and what is underneath. With any luck, it might be a couple of inches thick with a foot of hardcore below.

 

[tobydog]

Scott - what you haven't said is what you plan to replace the concrete with. Are you thinking of limecrete? Whilst you could incorporate underfloor heating into this, you do need to carefully consider what final top flooring you want because limecrete would require a breathable finish.

There are others on here who have done this and posted helpful blogs. Can't remember who they are right now but I would certainly recommend a search of this site to find them. Googling will help as there is a sustainable materials supplier in Wales called Ty Mawr who have their own specific process.

 

[jsmac]

Thank you everyone for your replies.

As way of an update I have attached a couple of photos - one showing what is under the floorboards and another of the underside of a floorboard.

Our builder who has dug a test pit outside with an aim to remove the concrete that surrounds and butts up directly to the house is confident that the foundation is deep enough to both lower the outside ground level and the level of the floor inside enough to allow for insulation.

My first question is what is on the underside of the floorboard and is it viable to remove it so that we can reuse the boards? It is solid but uncovering it has made the house smell like a roadworks site.

Secondly, any recommendations of what we should replace the concrete/bitumen/tar mix with once it is excavated? I presume limecrete would be a good choice but what could we use to provide some level of insulation?

As always any thoughts and recommendations would be most welcome.

Thanks.

Scott

 

[88v8]

Mmmm, that was thoroughly done.
Boards laid in wet, hot, bitumen, like parquet. That's as good as it gets.
The boards haven't rotted? No? So it was very well done.

Don't recall the age of your house. Is there a dpc? Presumably somethig was done back in the day to prevent the damp from running up the walls.

Here's my take: You don't have damp. Be very thankful.
Limecrete is no good as it's permeable and will release the damp, that's what it's meant to do, so you can't have limecrete below a wood floor.

In percentage terms, the heat loss through the floor is low, compared to walls and windows. Especially a wood floor. Forget insulating it. Leave it alone. Put the boards back, lay them again in wet hot bitumen. Leave well alone. The money you'll save by not changing the floor wil far far far exceed any savings you would ever make by insulating it.
Leave well alone.

Now, if you want to warm the floor, perhaps you could put electric underfloor heating on the existing boards and then another layer of boards on that. But my knowledge of underfloor heating is pretty much zero, so take advice from someone who is not trying to well you something.
I do know however that you can get carpet especially made for kitchens, that would warm things a little.
https://www.remlandcarpets.co.uk/flotex/?gclid=CNCbqef4vNQCFQ48GwoddQANBg

I would say it ain't damp so it ain't broke. Be very thankful. Very carefully reinstate it. Add carpet. Leave well alone.

Ivor

 

[jsmac]

Thanks, Ivor.

Unfortunately, several of the boards were rotten so I had to pull them up. The worst affected one was the board closest to and running parallel with the outside wall. It was sitting against it so had been slowly disintegrating. There was another patch of rot that affected several boards and when those boards were pulled up there was a thin oily substance on the floor and underneath the boards - a bit like the brownish colour of motor oil but thinner. I was wearing gloves so didn't touch it directly but perhaps it was simply trapped moisture? The hard bitumen is dry now at any rate.

All in I had to remove five boards but I was able to save a bunch of boards from the lower ground floor so I'm hoping they'll be an appropriate match. I think that your recommendation to leave the floor 'well alone' is sound advice. I can concentrate on improving the insulation in the room in other ways.

However, we still need to address the crazy fireplace that was built out to accommodate a 1930s tiled fireplace that we've removed. It wasn't very attractive (in our opinion) but more importantly its size was completely out of proportion with the rest of the room and where they've built out the fireplace it now blocks the window. We think the panelling was added in the 1960s when they added a gas fire. Basically it was a big tiled fireplace and gas fire that dominated the room. And not in a good way. Our hope it to rebuild the brick fireplace to a more sensible proportion and install a small Victorian insert and grate.

Thanks, again.

Scott

 

[Kearn]

I'll keep an eye on this thread - soon will be digging up a concrete floor laid over original bricks, which I so far believe to be laid on the ground in what was once an animal shelter (who knows until I start uncovering. What I am more intrigued by though is that fireplace??!!! Where does the flue route? what an odd incorporation!

 

[88v8]

Oh. So it was damp after all. Bummer.
Yes, that's likely damp from where the bitumen has debonded from the boards and allowed moisture to creep underneath.

Interesting in a bad way that damp has spread from the wall.
Easy enough to isolate the edge of replacement boards from the wall with a slip of dpc material, but is the wall itself damp? If so can you tell whether it's from external splash or rising damp?
Is the skirting rotten for example, or that cladding?

Given that the sub-floor is impermeable - concrete, bitumen - the typical consequence is that any underlying damp will go sideways into the wall, and without a dpc it may rise up the wall, the height of rise depending on the brick. What you are doing in lowering the external level is good, but bear in mind you may need to revisit damp issues in future if the wall is damp and does not dry. Could be a year before you know, as it can take that long to dry out.
Perhaps until you are sure don't for instance tile the bottom of the wall, leave it accessible.

With any damp in the wall there is a risk that it will spread back under the replacement boards. However, dry boards laid in wet bitumen again will nevertheless be good for a long time and you might take the view that nothing lasts for ever, and just reinstate the current arrangement. Indeed, if you would like a wood floor, any other route would be disruptive and expensive.

In the event you determine that there is rising damp, and you decide to bite the bullet and go for a limecrete floor, that would need a permeable finish, as has been said. Tile, brick, stone, laid and pointed in lime. One could then put a wool rug on it, but nothing impermeable. No wood.
Also, if you plan to put a modern kitchen in there with floor units, one should insert air grilles in all the plinths to release the damp.

Decisions decisions.

Ingenious fireplace. Home improvement as was.

Nice that the proportions of the room have been balanced by leaving the picture rail and maintaining a colour distinction between frieze and wall. So many home 'improvers' ditched the picture rail.
Not sure about the red though. Do like red, but that red hmmm or perhaps it's my monitor.

Oh, you mentioned the 6ft doorway. The doorway to the room where I now sit is 4'11" at the centre, Tudor arch, 4'8" at the springs. The kitchen doorway is lower. One can become accustomed, as have previous residents.
The ambience of a Period house is mutlifaceted. One can gradually tranform the Period house into a modern house by aping the conveniences. Before one knows it, the Period house with which one fell in love has disappeared. Just a thought.

Ivor

 

[Kearn]

Oh, you mentioned the 6ft doorway. The doorway to the room where I now sit is 4'11" at the centre, Tudor arch, 4'8" at the springs. The kitchen doorway is lower. One can become accustomed, as have previous residents.
The ambience of a Period house is mutlifaceted. One can gradually tranform the Period house into a modern house by aping the conveniences. Before one knows it, the Period house with which one fell in love has disappeared. Just a thought.

Ivor

we are fortunate with our 16C timber framed home in that most beams are just tall enough to not cause challenges for 'normal height' people, and that is with a later timber suspended floor downstairs raising from the original compacted earth floor when built. however, there is one exception in what you would think the most awful location - our bedroom door!! the height of the frame is perfect to strike you not on the forehead where you would see it coming, but right on the crown once you think you've made it through unscathed (which is agony!). it's a devious one, sneaking a blow from behind!

However, I think we both hit this (hard) a grand total of two times when we moved in four years ago. Only an idiot does it a third time is the usual logic we spout...! Remarkably we now happily wander in and out sub-consciously ducking just enough during the day / half asleep / after a few too many drinks in the middle of the night - you learn to live with these things and they give back amusing stories, that's our trade off!

 

[jsmac]

We've been living for several weeks now with a number of boards removed. The smell of bitumen is ever present and when there's rain the odd damp patch will appear in the exposed bitumen. The wet patches are not very big and dry out quickly enough but they tend to be isolated from the walls which makes me think the water must be coming up through the floor from below. The walls appear to be dry and surprisingly the timber cladding isn't rotten.

We've decided to replace to simply replace that damaged boards and leave the rest of the floor as is.

Ivor - you suggested laying the replacement boards in wet bitumen which is what we think would be a reasonably straightforward and cost effective solution. However, we've had a number of counter suggestions from various contractors that have been round to quote on other jobs - damp proof membranes on the floor and up the walls, etc.

Is there a product that you'd recommend so that we could do the work ourselves? Cutting boards to size and laying them in wet bitumen doesn't seem too arduous a task (the area is only about 3sqm) but perhaps we're being overly optimistic.

Many thanks.

Scott

 

[MatthewC]

Just re-reading this thread and I notice you say

The kitchen and dining room are extensions that we think were done in the mid to late 19th century and are the only rooms in the house that are actually at the same level as the ground outside. They are also the coldest rooms in the house.

...so are the other floors above or below the ground level? I can't see if you say this.

You need to make sure that your floors are all above the exterior ground level, preferably by 6" - 8". If the walls are breathable then that will help the inside floors to dry out. High ground is an often overlooked cause of dampness and people seem to tackle the symptoms instead of the cause!

 

[88v8]

We've decided to replace to simply replace that damaged boards and leave the rest of the floor as is.

Ivor - you suggested laying the replacement boards in wet bitumen which is what we think would be a reasonably straightforward and cost effective solution. However, we've had a number of counter suggestions from various contractors that have been round to quote on other jobs - damp proof membranes on the floor and up the walls, etc.

I'd use Isoflex liquid rubber
http://www.screwfix.com/p/isoflex-isoflex-liquid-rubber-black-2-1ltr/36010?kpid=36010&gclid=EAIaIQobChMIxpm8rIqu1QIV4Z3tCh3TUQTBEAQYAyABEgKdHPD_BwE&gclsrc=aw.ds&dclid=CNi3i7SKrtUCFeQT0wodXdcGEg
but check the maker's literature to ensure compatibility with bitumen.

The old boards are butted or tg ?? Looks like butted... Anyway, the boards won't be fastened down other than by the bond into the bitumen/rubber, so the boards need to be dry, or they won't bond. And straight.
I mention this because modern treated boards tend to be rather damp, and sometimes wavy. Fortunately you only need a small quantity, so a good timber merchant should be able to help you. Better dry and not treated, than treated and wet.

Vacuum the subfloor thoroughly, and use the manufacturer's primer on any bare concrete and let it go off. It's important to get good adhesion between the rubber and the concrete/bitumen, as well as rubber/wood.
Check the endgrain of the new boards. If there is a choice, lay them so they will try to cup downwards.
Coat the floor generously, lay the boards immediately.
Put heavy weights on them until the coating goes off, they need to be thoroughly pressed down onto the floor.

There is likely to be a thickness disparity between the old and new. May need to make up with hardboard or the like.

Damp membranes on the floor are only effective if the house has a working dpc. Otherwise it will just chase the problem higher up the wall, to bite you in the wallet in years to come.

Remember to ventilate well under any fixed cabinets - front, sides. Air movement can dry odd bits of damp.
9x3" or 6x3" here
https://www.inbrass.co.uk/acatalog/slotted-vents.html

Ivor

 

[jsmac]

Thanks, Ivor.

I spoke with the manufacturers technical advice team and they recommended against using Isoflex liquid rubber to damp proof an indoor floor. They said it is extremely smelly and it would take months (or longer) for the smell to dissipate. They were also reluctant to say whether it would even be compatible with the existing floor. It seemed like an ideal product but I guess it's back to the drawing board.

The boards are tongue and groove and they're actually nailed down as well. The nails are nearly 3 inches long and getting them out of the floor takes a not inconsiderable amount of force.

We've recovered enough floorboards from the lower ground floor (many were rotten and so we pulled them all up) that I'm hoping we'll be able to use as replacement boards in the dining room. Curiously, these boards are not T&G but have a very similar grain to the boards that were laid in bitumen. They were nailed into joists that were embedded into a rough and seemingly porous concrete-like floor. Removing the rotten and damp boards and a joists in the lower ground floor has done much to rid the room of the smell of damp. It's still not great but it is an improvement nonetheless. What to do with this room to turn it into a liveable space is a decision for another day.

But I digress... As you guessed the boards that we've recovered are a different thickness to the T&G boards they're replacing. They're about a quarter inch thinner and so I figured I would make up the difference with marine ply or hardboard as you suggested.

However, I still need to find a solution of what to put them in. Any further suggestions would be most welcome.

Thank you.

Scott

 

[88v8]

Urrgh. Disappointing.
I do find that some people in 'Technical Support' are more forthcoming than others. If a product has not passed official tests for use in a certain situation, there can be a reluctance to recommend it.
Example - Armillatox. Kills honey fungus. Been in use for decades. But EU testing is so expensive that the makers can't afford it, and therefore can no longer advertise it for its tried and tested purpose.
http://www.armillatox.co.uk/default.htm

Anyway, I digress... the problem with bitumen is getting things to stick to it, other than more bitumen.
And I had rather assumed that the process would be smelly, sorry.

CT1 will stick wood to concrete, it says. Even if wet.
http://www.ct1ltd.com/product-applications/how-to-stick-wood-to-concrete/
Question is, will it stick to bitumen.
http://www.ct1ltd.com/wp-content/uploads/bsk-pdf-manager/2016/11/ct1_product_info_sheet_10-03-2015.pdf
Hmmm, have to ask them.

They also have a waterproofer, WT1
http://www.ct1ltd.com/wp-content/uploads/bsk-pdf-manager/2017/07/WT1_P-Info_Sheet_15-06-2017.pdf
but it needs a dry surface and again, will it adhere to bitumen.

Sikkabond 5500S will accept bitumen, but needs a dry substratum
https://parquet-parquet.co.uk/products-page/parquet-adhesive-no-bitumen-removal/sikabond-5500s-bitumen-removal-parquet/

Hot bitumen would do the job...... but it will be smelly.

Ivor

 

[jsmac]

Contacting Thompson's technical support wasn't at all a lost venture.

Whilst they recommended against using Isoflex Liquid Rubber for this particular application they did suggest that I could call Spencer Coatings who are the makers of Bitumastic Standard Black. I called them yesterday and they in turn recommended that I call Liquid Rubber Great Britain who recommended Karnak 19 Ultra - http://www.karnakcorp.com/product/plastic-cement/.

It is applied with a trowel and so can be applied up to several cm if necessary. The chap I spoke with told me that I could use it to fill the holes and cracks where the solid bitumen has pulled up more than just bitumen so hopefully this is a solution. Moreover, it is designed to adhere to bitumen (and concrete) and while it will indeed be a smelly job the smell won't linger for many months (apparently). Result!

Thank you again for your continued support and suggestions. I'll have a look at the products you recommended - there will no doubt be further jobs that will require creative solutions.

I will update this thread once I get started laying the floor. I first need to break up the concrete outside and drop the ground levels. But before I do that we need to rebuild the small Victorian WC which is next to the above room in question. We (and everyone else) assumed was made up of solid brick walls but it is in fact simply a lath and rendered structure with no footings (ie.dropping the ground levels will be problematic). It's remarkable that it has stood as long as it has.

It is becoming clear to me that one job is never as simple as just that.

Cheers,

Scott

 

[88v8]

It is becoming clear to me that one job is never as simple as just that.

Glad you seem to have a way forward. Sometimes persistence pays.

Yes, some jobs become bogged down in a sequence of pre-work. There have been occasions when it's taken so long to do the pre-work, by the time I'm able to do what I want to do, I've decided I don't want to do it.

It's surpising how long a rendered structure can last. At our previous house, a neighbour's garage abutted one boundary. It was a dwarf wall with no dpc, a flimsy wood frame, and cement render on chicken wire. The wood frame was rather rotted so the render & chicken wire had become largely self-supporting. But there it was, still doing its job, at least sixty years old.
A lightweight structure needs no footings. Do not necessarily scorn to rebuild your WC as per the original.

Ivor

 

[88v8]

oops