1890s Victorian- sloped patio/subfloor ventilation/damp

[Ellis23]

Hello all,

We are buying our first house and before we exchange I'd welcome some friendly advice regarding issues highlighted by our survey.

Context: 1890s terraced Victorian house. Suspended floor throughout to the exception of kitchen (concrete solid floor built in 2002). Back garden was paved entirely same time (see pictures below).

The surveyor and we noted the following (see also pictures below):

1. Damp picked up in the kitchen extension, ground floor bathroom and dining room (although the three times I have been at the property there was no noticeable damp smell...maybe the carpets help)
2. High ground levels and the patio slopes towards the house and the side return
3. No ventilation at the back- only one to the far left corner of the side return and no visible airbricks at the front meaning the concrete extension is likely blocking all airbricks from original house (hence damp patches at the junction between the two and dark looking floorboards?)

Obviously being first time buyers we are now concerned that a) when we start investigating we uncover more damage as this would have been ongoing for 20yrs and b) that the cost of fixing these issues becomes prohibitive for us especially if we have to rebuild the extension as there is no side access to the patio from the street...). We are therefore questioning whether to buy at all!

So far we were thinking of:
1- digging a trench alongside the extension/the infill, fill it with gravel and in front of this install an ACO drain (our builder said only an ACO against the walls with no trench would capture all the water and the wall would dry but it feels like we should try to get the water away from the base of the walls entirely?)
2- get rid of all the paving in the second half of the patio so the ground can absorb that normally
3- we have not clue how to retrofit the rear ventilation other than ripping the kitchen concrete slab apart and running the air pipes properly

Would anybody have some advice to spare for us?...

Thanks a lot!

Ellis

 

[88v8]

Hello and welcome.

All this and horrible plastic windows, current owner isn't exactly period-minded then.....

Our first house was terraced, right pain barrowing stuff through the kitchen along the hall.... took tons of soil and rubble out that way and tons of readymix in when I built a slab out the back.

What can one say... you already know the answer... the 'patio' otherwise known as the can't-be-bothered-to-garden, needs to come up and be replaced by... a garden... and the ground levels lowered to 6" below the air bricks and the concrete slab in the kitchen has to come out or perhaps be diamond sawn if it's not too thick which it probably is, so you can pipe the air bricks through.

I wonder what's under the 'patio' maybe the rubble excavated when they built the kitchen? so the topsoil in which one would garden is buried. Calculate the tonnage you need to shift and the barrowloads.

Killing the underfloor ventilation is never a good thing and the problems you can see are just the problems you can see at the moment.

And on a minor note, that downpipe on the side doesn't seem to go anywhere?

If you were experienced DIYers and up for a lot of mess and the house is cheap, I'd say go for it. Otherwise I'd give it a miss and be thankful I'd dodged a bullet.

 

[Ellis23]

Thanks a lot for your response 88v8, really appreciate it.

Indeed, not period minded at all so we would have liked to give the house the love it needs.

Are you thinking rot when you say “other problems”?…

We’d indicatively costed about £15k to put this right- do you reckon we’re miles off?…

I was thinking if it’s more than that we sort out the ventilation and the drainage installation/ ground levels but leave the rest of the patio as is until we’ve saved enough to get rid of this horrible patio…

 

[a twig]

If it were me, I’d look at the following:

Lift and remove the patio myself so probably only a couple of skip loads ~ £500 ish? Then some grunt work with spade and rake to slope it away from the house. Potentially then another ~£200 on topsoil and grass seed if needed. Call it £1k with contingency.

You could try to create some additional ventilation by ducting under the floorboards where it meets the kitchen and venting it out the side, not ideal but it could help. Lifting the floorboards will also reveal how wet it is under there and thus how much of an issue the ventilation really is. Something like that would be DIY-able with the purchase of a cheap SDS and core set and the relevant vent parts from Screwfix or similar - perhaps £500 in tools and parts. Just make sure you don’t damage the DPC in doing it.

Or more controversially but less intrusively you could install hit and miss grilles in the floorboards at the edge of the room so you can open them during the summer to ventilate but close them down during cold snaps to save on heating etc. Again not ideal but it’s a potential cheaper and easier option.

I’d pay for someone to do the bit along the side where the concrete is as that’s a horrible job and you’ve got drains there - which is always helpful to have any potential damage covered by someone else’s insurance. I would have said maybe £3k for that but groundworks prices are all over the shop these days, a friend was quoted £7k last week for a 4m by 5m concrete slab patio

Just to repeat - that’s what I would be thinking based my experience and on the info you have provided - use at your own risk, T&Cs apply, value of investments can go down as well as up etc.

 

[88v8]

Are you thinking rot when you say “other problems”?…

We’d indicatively costed about £15k to put this right- do you reckon we’re miles off?…

I was thinking if it’s more than that we sort out the ventilation and the drainage installation/ ground levels but leave the rest of the patio as is until we’ve saved enough to get rid of this horrible patio…

Yes, after twenty years I would be concerned there might be underfloor rot.

If ground levels at side and rear were lowered to 6" below dpc an ACO drain would not be necessary. The original air bricks at the front of the house are probably sitting on the dpc so that gives you a benchmark.

Having done that... vents... the Twig has some ingenious thoughts... one could vent out to the side... I don't see any vents in the side passage either...?... but there needs to be air movement beneath the entire floor so that doesn't help the far corner.

Hit & miss vents in the floor could work... one in each corner one or two in the middle... assuming of course you don't have fitted carpet up to the edge, it could help provided there is a fireplace in the dining room, an real open fireplace I mean not just an ornamental one, as the fireplace or rather the chimney would create a permanent suction to provide air movement under the house from the front vents. But it still doesn't help the corner under the stairs and without a fireplace there will be little air movement anyway.

If no fireplace, and I do not see one on the plan.... back to the side venting... the need is to create air movement beneath the entire floor... any dead zones will be prone to damp... so you put some 4" solid plastic trunking under there with two intakes, one in the far corner beneath what looks like the cupboard under the stairs, and one under the middle of the dining room floor and connect the ducting to an exit in the side passage and in the trunking towards the passage side of the dining room you put an inline fan like this for instance which I pick mainly because it is reassuringly expensive, and you run it twice daily for 30 mins on a timer. Obviously need to provide a permanent underfloor access so you can get at the fan to service the filter.
Prop up the ducting so it's not sitting on the subfloor where it will pick up dust.

That would create the air movement you need.
Quiet enough not to be annoying but loud enough that you'd hear if it packs up.
And even the largest of the three fans in that link is only 100 watts so the running cost would be piffling.

This assumes of course that ground levels and absence of air movement are the only causes of the damp, but they are generally the main culprits, and assuming Twig's costs for sorting the levels it could leave some change from your £15k.

As regards drying out, reckon 1 month per inch wall thickness.

Ivor

 

[Ellis23]

Both,

Thanks so much for your time and thoughts- really really appreciated.

If the seller agrees to a reasonable price reduction I think we will go ahead with it and cross our fingers it is a manageable issue. Am thinking if it was a complete ventilation/ damp fail and the extension was built 20yrs ago you’d see and smell a lot more damage? (maybe wishful thinking, we’ll find out soon!)

We’ll lower those ground levels, peak under the floorboards and sort out ventilation as soon as we have the keys and see how things look in two months when it should have dried out.

Now we just have to find a builder in North London/ Herts with genuine interest in period properties- otherwise I think you’ll see me posting a whole lot more over the coming year, sorry!

Ellis