Bitumen/Asphalt Floor (ex-Council house)

2 Oct 2004
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Sunny Hampshire.
United Kingdom
I'm doing a kitchen modernisation in my ex-Council house which was built in 1947. Like a lot of houses of that age, the ground floor is bitumen/asphalt over a concrete screed. The bitumen is about 20 mm thick and, I believe, serves as moisture barrier as well as an 'appearance' finish.
The floors are not level and have various cracks and dents. The kitchen units have adjustable legs so they aren't a problem but the built-under oven unit has two melamine chipboard sides which should rest on the floor for their whole length. To get the unit level as a try-out, I've had to put 15 mm of packing under the rear of each side-piece but that's no good long-term because the weight of the oven won't be uniformly distributed. I don't fancy tapered packing pieces (450 mm long) so I thought of levelling compound. I've browsed most of the relevant threads on this forum and found the link to RMC Biscem LF25 which looks promising. Please can anyone give me guide prices?

My past efforts to find anyone who is really familiar with this sort of bitumen floor and its care and maintenance have been unsuccessful; I get the impression they've mostly all died off! I'd like to tap some know-how on this subject - I've got all sorts of repairs to do in the other ground floor rooms when I've finished the kitchen.
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BruisedThumb said:
The bitumen is about 20 mm thick and, I believe, serves as moisture barrier as well as an 'appearance' finish.
Are you sure it's 100% 20mm bitumen and does it fell spongy or it is rock hard ?
Hi, thanks for your reply.

I can't be sure of the 20 mm, it might be 15 mm, it could just be 25 mm in places but it's that sort of order of thickness all over the ground floor.

It's a dark brown in colour and yes, rock hard, quite brittle. I tried heating some small pieces and it melts although it's obviously a poor conductor of heat; there's a tendency for the outside to burn before the inside of the lump becomes liquid. When it does melt, there's evidence of it having some sort of filler.

When I lived in Surrey, the family of one of my school chums moved into a new Council house which had such a coating on the ground floor except that theirs was dark red and not so hard (hardens with age?). They were told not to put down carpets for the first twelve (??) months. I remember reading press reports that folks elsewhere who disregarded this warning found later that their carpets had been 'wetted' by the top layer of the bitumen and couldn't be removed without damage to both floor and carpet.

In my kitchen floor there are four dents where presumably one of the old cast iron cookers (e.g. Creda) probably stood for a few decades. There's also a crack which probably marks the join between two successive batches or mixings of the material. There are also some similar sets of dents in the living room floor where I presume heavy items of furniture stood. (I don't think they had a piano :) ) I hope to lay wood-strip flooring in the living room and laminate in the hall and dining room.

However, since the area where I want to put my oven unit slopes back by 15 mm in about 400, the material can't have been very runny when it was laid or it would have self-levelled then.

If you are acquainted with this material, I shall be grateful for any hints and tips you care to offer.
BruisedThumb said:
If you are acquainted with this material, I shall be grateful for any hints and tips you care to offer.
I'm work with bitumen as I work for a oil refinery and make them ready for supplier.
Somehow I not sure if it's bitumen because bitumen is black and not dark brown colour unless it's ruberoil such as Synthaprufe. I never come across of bitumen being 15mm or 20mm thickness because of a softening point at room temperature unless you have tarmac ;) Sounds like you have 95/25 pen bitumen which is use for flat roofing felt but not at that thickness. You can put a flooring compound over it but I'm concern about the thickness of it. A bit awkward without looking at it. :cry:
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Hi there, Masona,

Thank you for persevering with this topic.

As I remember it, Synthaprufe was developed by the National Coal Board research laboratories during the time that Dr. Bronowski was in charge there. I know that some canal boat owners used to paint the underwater parts of their boats with it. What I mean is that I thought Synthaprufe was more a paint or thin layer coating than a floor topping compound like I have.

I've also been told that I should have used it (i.e. Synthaprufe) to make good the damp-proofing where I've chased my kitchen floors for the MICC cables; told too late, I'm afraid! I refilled the chases with mortar coloured orange as that's the colour code for electrical services. It's off-topic but I'm a believer in a house having a log-book with all the locations of stop-cocks and main switches and cable routings and similar stuff. Mine will mention the significance of orange mortar.

To be honest, I'm a bit confused between the difference between bitumen and asphalt. We talk about asphalt for roads as a synonym for Tarmac but I think that's not correct, Tarmac has the stones added, the asphalt is just one ingredient.

As I said in my earlier post, my flooring compound does have some sort of mineral (?) filler but it seems to be quite fine.
I have come across this type of floor many times when surveying insurance claims for water damage. It is sometimes dark brown, and can be laid at 25mm, thick. I also see it a lot in now in Delivery Offices for a certain well known mail company, where it is laid at 35mm thick. In your property it will have been used as a damp proof membrane. Whilst I know it is defeating the object of diying, I have always had the luxury of appointing a competant sub-contrator to do the work. Some things in my opinion can be a specalist job. My Sub-con always refers to it as Mastic Asphalt. Try looking at a company called Ardex for levelling compounds and repair mortars, but rmember the damproof qualities of the bitumen should not be compromised.
I must admit I never came across this before, so do they use this instead of dpm ? If so what level is it at ? Inline with dpc to the side ? Is this material rock hard ?

Thank you for your post on this topic.

It was my understanding that this material was very popular, especially for Council houses, in the late 40s to maybe early sixties but that it then went out of fashion, presumably replaced by some other process.

That would mean it only comes up in the repair context nowadays. Am I right in this or do you know of its being used in new construction in, say, the last 20 years?

I'm thinking that there would have been more 'know-how' about if the material were still employed for new construction.


I can't remember exactly where the dpc is in relation to the FFL, I'll have to have a look.

The house is not conventional bricks and mortar; it's a Laing 'Easyform' (or should it be 'Easiform'?). No-fines concrete walls cast in about 20" lifts in a big plywood mould. The aggregate seems to be some sort of industrial slag. Above dpc, the walls are cavity, two leaves 3_1/2" thick with a 2" cavity. I believe there are reinforcing irons in the concrete above the openings in lieu of discrete lintels. The external leaf is finished with tyrolean render. My particular house has also been treated (by a previous owner) with a plastic finish (that looks as though it has a muesli filler :) ), that's worth a post of its own, but not here.

The walls seem to be of conventional concrete below dpc.

As this is the floors/stairs/etc department, I won't say anymore about no-fines concrete walls here. Maybe I'll search in the 'building' department.
Could you not chop out the whole floor of the width of the kitchen unit and make goods with sharp sand/cement or levelling compound ? This will give a good base for all the unit as well.
Thanks for your post.

I'm feeling a bit small regarding levelling compound at the moment. :oops:

Following a link I found in another DIYnot thread, I bought some RMC LF25. The data on their web-site said it would cope with up to 30 mm thickness if 'bulked' and would adhere OK to asphalt if properly prepared.

Before I go on any further, I must emphasise that nothing I say here is meant as a criticism of RMC or their product; I handled it wrongly. But I'll recount my experience here; it might help other DIYnot readers.

I didn't understand the term 'bulked' but their rep explained that this simply meant adding some suitable aggregate, e.g. finely crushed stone or sharp sand.

So, yesterday afternoon, I had a go. I calculated that I didn't need to mix the whole bag + bottle so I tried to measure out the right quantities to maintain the right proportions between liquid and powder. (their data sheet says that a whole bag of powder goes with a whole flagon of liquid.) I'd also read on here but forgotten that the right consistency was 'like custard'.

I obviously got mine too thick, it went off too quick to self-level and I didn't get an opportunity to mix in any aggregate. It didn't take too kindly to being trowelled-out, especially at the thin edge. I'm going back tomorrow to see how it's turned out (I should explain that I'm not actually living in the house at present.).

If there are a few ridges, I might try gently tickling them with the angle grinder. However, if that threatens to loosen it from the asphalt, I do have enough material left to have another go.

I prepared the asphalt surface by going over it first with a scraper and then a wire brush, then washing with white spirit then water + washing-up liquid and finishing off with fresh water and drying with a cloth and bits of kitchen roll. Then I had a 'cuppa' to give it a chance to dry off before I even started to mix the levelling compound.
Sorry been away for a few days and thought I come back and check the thread. This stuff (ashphalt) is as far as I know no longer used in modern housebuilding, as the dpm usually consists of visqueen laid under concrete, along with insulation (styrafoam, expanded polystyrene etc). This is joined into the dpc, forming a sort of 'tank'. The dpc is usually at least 2-3 courses above the outside ground level if I remember correctly, (I was involved in some house building 87-93).

The ffl on a timber floor is joists plus floor boards sat on or above the dpc, (joists thickness depends on floor span) . The ffl on a concrete floor is generally level with the dpc, this is possible due to dpm being lower down.

When I used a leveling compound the ridges where usually just trowel marks, or lumps from bad mixing and a carborundum stone on a wooden base with handle was used to rub these down.

Just a note of caution, I have come back from a occupaitional Skin Management seminar today and one of the things I learnt is that turps is absorbed and permeates straight through your skin to be absorbed into the bloodstream. Apparently this can be demonstrated by rubbing a cut juicy garlic clove on the palm of your hand and we were told that you can smell it on your breath 5 mins later. Even worse was a tale told by the consultant were people washing ink of their hands at a factory with methylated spirit had their eyes checked by an optometerist 20 mins later and were found to have eye damage that took the body 5 hours to repair.
this stuff will even permeate through certain glove materials without actually damaging the glove material. Sorry to be a health and safetey bore, just thought you may want to know, although sometimes you are better off not knowing.
Hi there, Fez, welcome back and thanks for your post.

Since my own last post, I've had another telephone conversation with the RMC rep. He pointed out to me that LF25 is actually not a self-levelling compound; it's described on the bag as a 'smoothing compound' and does have to be trowelled.

I've put down the third application this afternoon (Thursday) to try to bring my bit of floor up to level. I packed the built-under oven base up yesterday and mixed some LF25 fairly thick and trowelled it under the sides of the base. Then today, I removed the base and applied some more in between those two ridges using them as a guide, levelling it with a batten. I don't find it easy to get a good surface with the (plasterer's) trowel so I may finish off with an actual self-levelling compound.

Regarding your health & safety points, well it's foolhardy to ignore proven hazards, once they are proven that is. The problem is that many of them (e.g. creosote) have only recently been identified. I'm old enough to be able to remember when only one variety of asbestos was considered dangerous and solvents like Carbon Tetrachloride and 'Trike', even Xylol, were in common use. A work colleague some years ago went on a Health & Safety course and came back with some real horror stories about soldering and brazing fluxes.

There are some real-world difficulties, though. I know that I should wear both dust-mask and safety glasses when I'm using the angle-grinder; the problem is that when I wear both, my spectacles mist up and I can't see what I'm doing. That poses a different sort of hazard! I intend to try the modern dust-masks which have a built-in exhaust valve.

I believe what you said about skin absorbtion. I was told almost the same thing about the garlic recently except that it was 'rub the garlic on the bare sole of your foot' and taste it ten minutes later. That particular conversation was in support of wearing gloves when pulling Ragwort.
Hi Pete, just come across your post on Bitumen/Asphalt Floor which was posted sometime ago. I'm just wondering how you got on and what solution did you end up implementing and was it successful?

I ask as I have a similar problem.

I initially was going to use bitumen products to repair the areas them use a leveling compound but now I'm not so sure.

Seems really difficult to get the answers and a tried and tested solution for the problem.

You help is much appreciated


Trying to source any information on this floor topping materials from an older building I'm working on. While removing, it smells like topsoil. Tried to remove and patch areas with a concrete patch that didn't bond. Scratching my head.


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Hi Andy . Are you actually in Canada ? I've not seen anything like that over here UK with those lumps o_O unless it's a form of cork and some bonding agent - possible in the cold of Canada to insulate the floor.

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