Help Please! – Subfloor/Foundations

[Aidan_1983]

Hello everybody, I have just purchased my first house and have come across a possible issue with my subfloor/foundation, which I hope can be resolved.

We have had the walls knocked back to brick, a damp proof course and wall membrane installed and just recently, plastered throughout.

Next, I planned on working on the floors, which is currently covered with original timber planks. I planned to make the floor flat throughout my downstairs, by boarding and creating a subfloor, which my laminate flooring would then be fitted on top of.

Problems started to arise when I found that several of the original planks in my back room looked rotten. I decided to replace them and continue with my plan. To my shock once I had removed the first plank, I revealed a layer of condensed black ash, which the planks were laying on top of. I have found that this black ash substance is over a foot deep and encompasses the whole of my back room, some 16 meters squared. My house is open plan and it does not extend to my front room, kitchen, which is concrete, or my hall.

After inviting a builder to survey the situation, I have been told that my only option is to big all this compact dust/ash out and to lay a concrete floor. He informed me that he believed this construction method to be outdated and a danger to the integrity of my house; furthermore it no longer meets building regulations.

Could somebody clarify this? I first thought well, I’ll need to put a membrane down to stop any damp coming back through to my new planks and boards, then replace and install new planks and continue to create my sub floor, but his comments and reaction makes me think I am just going to have to shell out the 6 grand it is going to cost for a concrete floor installation. Plus, I have been reading online that if not done properly the ash can react with the concrete and cause cracking.

Please could anybody with experience with this type of flooring substance offer me advise as to which rout I should go down? – Any help would be much appreciated.

I have attached some images to give people a better perspective.

Kind regards,

Aidan Courtney

 

[^woody^]

What are the boards fixed to? Joists?

Are there any air bricks around the external walls at ground level?

 

[Aidan_1983]

There are some airbricks / vents around the outside of the external wall, at ground level, yes. You can see them at the front of the house and at the side. The current boards are fixed to joists, which is the same as the front room, but there is to hardcore ash infill in the front room or the hall, just joists.

 

[^woody^]

This seems to be some whacky scottish method of building. If that is so, then it must be OK, and you only need to find the cause of the localised dampness.

Otherwise just scrape the ash out or to a reduced level

 

[Aidan_1983]

Scottish, funny, well I am not that far north. This property is in Wigan and it is probably pit ash and debris from the local mines (What I am told). I am just concerned as I have started to read about this method of infill being related to sulphate damage. If slabs are used or concrete placed over the top it can causes the cement or slabs to crack and deteriorate. The thing is, I am not looking to do that, I just wanted to stop any damp, patch it up and board it. The builder I got in to have a look, put the fear of god into me and said it will cost over 5 grand, plus he said it was my only option. The house was built in 1908 and in the 40’s this sort of infill was common practice. I have read in a direct gov document that houses build between 1900 and 1950 could have hardcore infills like this which are a metre and a half deep. God knows how much there is down there. If we go down the avenue to pulling all this black ash hardcore debris out, I am just worried we might uncover other issues or create other problems.

 

[Nige F]

The piece of wood lying across the fireplace - is it covered with bitumen, or just blackened by the infill ?

 

[^woody^]

@tony1851 is a local lad and I'll look forward to his view on this northern madness.