Floating Flagstone kitchen floor ... HELP needed please!

[Anni]

Hello
This is my first post so I am trying to find my way around!

I have a weavers cottage dated 1810, it has a floating flagstone floor over the basement., everything seems to be structurally sound but over the past 12 months I have noticed some of the stones getting a little more wobbly than usual and a few stones have cracked (the floor has been on my list of jobs that need looking at for 20 years but life has got in the way!). The stones are very close together, theres no pointing as such. I dropped a cast iron pan and the stone it landed on broke ... HELP is needed because the story gets worse from here .. I have had various work persons come to look to offer quotes but none seem to have dealt with this type of floor and I cant find anyone that suggests anything other than lifting and laying on cement, pointing with cement etc .. its flagstones laid on beams and then some sort of dirt on top (with mussel shells added?!!) and then another layer of flagstones on top .. i doubt that many of the stones have been lifted since they were originally laid 200 odd years ago BUT yesterday myself and my son lifted one of the stones to see what was happening underneath .. Im now petrified! It is obvious that at some point there has been a mouse issue (we ve had an odd one appear at times but never noticed a great issue and we havn't caught any in our resident trap for maybe 2 years) but there are obvious grooves in the dirt between the flagstones that I would say are mouse tunnels. My other concern is that around the edges of the stones look hollow (maybe from years of vacuuming and sucking up the dusty dirt through the gaps??). Im guessing that the stones are going to need lifting, re-laying and repointing. Sorry for the rambling long story but now to my real questions ... What products should be used?. How do we fill voids that run under flagstones that run under the fitted kitchen units?. Is this a job that my son and i could possibly do and if not what sort of a trades person am i looking for that would do this sort of job with finesse and in keeping with its age? Im lost and not sure where to start! Any help/advice would be greatly appreciated .. Thank you

 

[Cubist]

Hello Anni and welcome,
I took a step back when I first saw your post in the hope that one of the other members may have some direct experience of a similar floor; my own is rather weak and distant now and has on;y the broadest similarities to your challenge. That said, here's my two-penneth in the hope that someone may come along to provide better.

Overall I would not be too worried by the apparent mouse burrows nor feel that these should be a source of alarm or worry concerning the integrity of the floor. When you stop for a moment and realise that mice and other wee beasties have had 300 years to explore the cavity between the two layers of flagstone and construct their tunnels its guaranteed that quite a few will have tried long before now. Mostly, mice will only try to take up residence during the winter months when they are seeking shelter and warmth. Unlike some small mammals though they do not hibernate and will spend much of their waking hours foraging for food and water and in those expeditions can cover a much larger territory than might be expected. Given that the floor concerned is one suspended above a timber frame of some sort its likely that the mice/whatever have found their way in from outdoors and have simply taken over the existing burrows when they have come across an existing opening. Almost any counter-measure you take, including the use of gases, will only produce short term results and - like Arnie - they'll be back. However if you can find the places, there may be more than one, they are using to get under the flagstones, then you at least have a chance to block them.

Regarding the flagstone floor. I can well understand why the various contractors you have spoken with have sucked on their teeth and said "best take it all out and re-lay it". Please don't. It's not necessary for one or two flags showing signs of movement and fewer still with cast iron pan damage. By way of information; builders will have used almost anything that came to hand to use as bedding material for flagstones and such often included sands and fine gravels gathered from nearby beaches and river estuaries which often contained small fragments of shell.

One of the reasons why contractors will have been seeing pound signs in front of their eyes is that very often the flagstones used by the original builders may have been wildly different thicknesses and also weights. As such it can be very difficult to establish a consistent level at the surface without some arduous trial and error with some potentially very heavy lumps of stone. Many modern builders will, while repairing or relaying such a floor, use a 'dot and dab' technique in which mounds of mortar are arranged at the corners and centre of each opening for a slab and the slab then tamped down to the required level. This echos, I believe, the technique used by the original builders who would have done the same using dry or semi dry products such as sand, ash and the like but perhaps blended with a little lime.

This same approach can be used to re-lay the slab you've already lifted with help from your son. Personally, I would simply clear the existing sand/infill from small areas in each of the corners and centre of the opening as more material from beneath neighbouring slabs may, in effect, wash/collapse into the new void after the slab is replaced. In terms of grouting between the slabs bluntly I would not use anything that sets, like a mortar, as it would be better to use something with a consistency similar to the existing bedding material as this that can flow down under its now gravity over time to fill cavities that develop near the edges of the flagstones. However, if you use this approach you should remember not to use a vacuum cleaner on this floor and nor should you allow it to get excessively wet.

Sorry for the lengthy reply but I hope this will be helpful.

BTW If there is another flagstone in that floor of the same dimensions as the one with husband head damage then you might consider a swap.

Cheers,
Cubist

 

[mardinor]

I'd advise the following options:
1) Ignore for another 20 years..the worst that happens is they wobble a bit. Perhaps buy aluminium pans.
2) Selectively lift the worst offending slabs (vacuum lifters and crowbars) and chuck a bit more dirt under them until they stop wobbling
3) Call SPAB for advice, then try to get skilled tradesmen to quote, then baulk at the cost, then wish you'd never started and revert to option 1

 

[Anni]

I'd advise the following options:
1) Ignore for another 20 years..the worst that happens is they wobble a bit. Perhaps buy aluminium pans.
2) Selectively lift the worst offending slabs (vacuum lifters and crowbars) and chuck a bit more dirt under them until they stop wobbling
3) Call SPAB for advice, then try to get skilled tradesmen to quote, then baulk at the cost, then wish you'd never started and revert to option 1

Thankyou for the reply .. lol

The problem isnt just that the stones wobble, they are starting to crack and the one we looked under showed that there are some significant voids under the edges. Looking at options and thanks for mentioning Vacuum lifters, we are looking into these. I have been trying for weeks to get in touch with SPAB but no one answers the phone?!

 

[Anni]

Hello Anni and welcome,
I took a step back when I first saw your post in the hope that one of the other members may have some direct experience of a similar floor; my own is rather weak and distant now and has on;y the broadest similarities to your challenge. That said, here's my two-penneth in the hope that someone may come along to provide better.

Overall I would not be too worried by the apparent mouse burrows nor feel that these should be a source of alarm or worry concerning the integrity of the floor. When you stop for a moment and realise that mice and other wee beasties have had 300 years to explore the cavity between the two layers of flagstone and construct their tunnels its guaranteed that quite a few will have tried long before now. Mostly, mice will only try to take up residence during the winter months when they are seeking shelter and warmth. Unlike some small mammals though they do not hibernate and will spend much of their waking hours foraging for food and water and in those expeditions can cover a much larger territory than might be expected. Given that the floor concerned is one suspended above a timber frame of some sort its likely that the mice/whatever have found their way in from outdoors and have simply taken over the existing burrows when they have come across an existing opening. Almost any counter-measure you take, including the use of gases, will only produce short term results and - like Arnie - they'll be back. However if you can find the places, there may be more than one, they are using to get under the flagstones, then you at least have a chance to block them.

Regarding the flagstone floor. I can well understand why the various contractors you have spoken with have sucked on their teeth and said "best take it all out and re-lay it". Please don't. It's not necessary for one or two flags showing signs of movement and fewer still with cast iron pan damage. By way of information; builders will have used almost anything that came to hand to use as bedding material for flagstones and such often included sands and fine gravels gathered from nearby beaches and river estuaries which often contained small fragments of shell.

One of the reasons why contractors will have been seeing pound signs in front of their eyes is that very often the flagstones used by the original builders may have been wildly different thicknesses and also weights. As such it can be very difficult to establish a consistent level at the surface without some arduous trial and error with some potentially very heavy lumps of stone. Many modern builders will, while repairing or relaying such a floor, use a 'dot and dab' technique in which mounds of mortar are arranged at the corners and centre of each opening for a slab and the slab then tamped down to the required level. This echos, I believe, the technique used by the original builders who would have done the same using dry or semi dry products such as sand, ash and the like but perhaps blended with a little lime.

This same approach can be used to re-lay the slab you've already lifted with help from your son. Personally, I would simply clear the existing sand/infill from small areas in each of the corners and centre of the opening as more material from beneath neighbouring slabs may, in effect, wash/collapse into the new void after the slab is replaced. In terms of grouting between the slabs bluntly I would not use anything that sets, like a mortar, as it would be better to use something with a consistency similar to the existing bedding material as this that can flow down under its now gravity over time to fill cavities that develop near the edges of the flagstones. However, if you use this approach you should remember not to use a vacuum cleaner on this floor and nor should you allow it to get excessively wet.

Sorry for the lengthy reply but I hope this will be helpful.

BTW If there is another flagstone in that floor of the same dimensions as the one with husband head damage then you might consider a swap.

Cheers,
Cubist

Thanks for your reply .. I have calmed a little but am still a tad anxious about tackling this job lol.
We have been around a worked out which stones are 'delicate' and need looking at in more depth. The wobbles arent really an issue but the cracks are. The ones with issues are the ones that are on the main walk ways .. they arent protected by rugs and the grout and probably the dirt they sit on has most likely been removed by mice moving things around and then hoovering sucking it up through the gaps. Everything under rugs and furniture seems to be ok.
The slabs are various sizes but when we lifted the one we did notice that the surrounding ones did look somewhat consistent in depth .. fingers crossed! We have decided to just lift the problem 5-7 slabs (hopefully with a Vacuum lifter (we are looking into hiring) and we are researching as much as we can before hand. Your advice has been noted .. Thank you

 

[mardinor]

If the stones are effectively bedded on other stones, then this is a bit like patio slabs laid on hardcore. In that situation, cowboys will put dabs of concrete in the corners, which causes cracking due to uneven support. The answer is a full bed of support. This is usually a mortar mix, but sand is also used. In a garden, sand can get washed away, but in your context might be ideal.
So a more helpful suggestion would be to lift individual slabs using the vacuum lift then re-bed onto sand
Perhaps google how to replace broken patio slabs for inspiration?

 

[a twig]

its flagstones laid on beams and then some sort of dirt on top (with mussel shells added?!!) and then another layer of flagstones on top ..

Anni, when you say flagstones laid on beams, is all this stone laid over a suspended floor?

 

[Anni]

Anni, when you say flagstones laid on beams, is all this stone laid over a suspended floor?

There are the beams and then flagstones laid over the beams, a layer of dirt and then another layer of flagstones.. frightening when you think about all that weight!

 

[Anni]

If the stones are effectively bedded on other stones, then this is a bit like patio slabs laid on hardcore. In that situation, cowboys will put dabs of concrete in the corners, which causes cracking due to uneven support. The answer is a full bed of support. This is usually a mortar mix, but sand is also used. In a garden, sand can get washed away, but in your context might be ideal.
So a more helpful suggestion would be to lift individual slabs using the vacuum lift then re-bed onto sand
Perhaps google how to replace broken patio slabs for inspiration?

That is probably what we will try to do .. some of the flagstones are quite a size though. We are thinking 4mm fine grit sand (quarried rather than sea, to regulate salt content) 3-1 NHL .. Haha listen to me, this is advice Ive been given but in reality I have no idea what it means but im googling like mad!

 

[Zebra]

You say that the gaps are small, but would paving sand (easily available from DIY stores), if brushed into the gaps, find its way down to fill those gaps and resupport the flagstones where they're wobbling? Got to be worth a try?

 

[Stevers]

If there's a problem sourcing slabs the right size and type to replace the cracked slabs you could consider using epoxy resin to glue the cracked slabs together. I've done this with Araldite Standard for a broken Bradstone Old Town concrete slab laid outdoors. It was one of the few large slabs in their patio pack and I needed all of them to finish the job. For extra strength they could be pinned. My local independent DIY store sells 6mm Stainless threaded bar, and that is what I would use use as any left overs can be used outdoors for plastic stone repairs.

 

[Anni]

If there's a problem sourcing slabs the right size and type to replace the cracked slabs you could consider using epoxy resin to glue the cracked slabs together. I've done this with Araldite Standard for a broken Bradstone Old Town concrete slab laid outdoors. It was one of the few large slabs in their patio pack and I needed all of them to finish the job. For extra strength they could be pinned. My local independent DIY store sells 6mm Stainless threaded bar, and that is what I would use use as any left overs can be used outdoors for plastic stone repairs.

I shall have a look into this .. you have given me something to think about! Thank you

 

[Anni]

You say that the gaps are small, but would paving sand (easily available from DIY stores), if brushed into the gaps, find its way down to fill those gaps and resupport the flagstones where they're wobbling? Got to be worth a try?

I dont think so because we didnt realise how much has been vacuumed out over the years .. i think we can access most of the problems by lifting 6 ish flags and then maybe brushing sand down the rest to try to ensure they stay put. It is very much fingers crossed as we go

 

[88v8]

A stonemason could cut new stone, although not so easily replicate old wear patterns.

Vacuum lifters need a smooth surface. You may get somewhere with two or three wide bolster chisels around the edge.

I do agree, disturb it all as little as possible. As regards the kitchen units, that sounds rather modern. An unfitted kitchen would perhaps be more in keeping and give easier access for maintenance.

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