concrete mixture to stop water draining into foundations?

karaman · 26 Aug 2010

hallo,

recently bought property. there is a path of 20 inches around the house that slopes into the foundations. i aim to concrete it over with an appropriate slope away from the house. four questions.

1. should i use only sand and cement - this is the existing mixture - or some sort of ballast and cement

2. what should be the mix ratio

3. would lime be necessary for flexibility as we have very hard winters

4. what is the correct slope away from the house

thanks

karaman

noseall · 26 Aug 2010

1. should i use only sand and cement - this is the existing mixture - or some sort of ballast and cement

Use 6 parts ballast to 1 part cement and add enough water to facilitate mixing and workability.

2. what should be the mix ratio

As above.

3. would lime be necessary for flexibility as we have very hard winters

No. Once the concrete has hardened, temperatures will have little effect upon the concrete provided it is mixed and laid properly.

4. what is the correct slope away from the house

1:80

JohnD · 26 Aug 2010

if the house has a dpc, the path should be about 9 inches below it. As well as penetrating damp, rain will bounce off the path and splash onto the wall. You may need to dig out the old path to keep the ground level low enough. The old one can be broken up and used as hardcore under the new one.

the new one needs to be about 100mm thick concrete

make it wide enough to walk round with ease even when you have put plant pots and things on the path. Consider if anyone will ever need to take a pram or wheelchair along the path.

karaman · 27 Aug 2010

hallo noseall and johnd,

grateful to you for the information. would have taken this little old lady ages to find out from a book!

there's no dpc - will remove 30cm soil from around the house so it is higher than surrounding area, create sloping concrete path away from house and fix the guttering. Replaster inside with 'breathing' plaster. Will see this winter if these will do the trick.

there will probably be more questions when the time comes but for now,

thanks again

karaman

noseall · 27 Aug 2010

JohnD may have been a bit overzealous (regards 9" below) as regulations insist upon a minimum of 150mm below dpc for any external paving.

This equates to 2 (metric) courses of brick below dpc. This in turn usually means having a step outside your external doors.

karaman · 28 Aug 2010

hallo all,

30cm below current level means ill have to fabricate a slope to my front door anyway

i'll be using a wood-burning stove in the lounge. should i have a brick with holes in it on the bottom of the wall furthest away from the stove?
(im getting pictures of spiders taking refuge in my lounge)

thanks

karaman
the spirit never dies
+++++++++++++

stuart45 · 28 Aug 2010

karaman said:
hallo all,

i'll be using a wood-burning stove in the lounge. should i have a brick with holes in it on the bottom of the wall furthest away from the stove?
(im getting pictures of spiders taking refuge in my lounge)

thanks

karaman
the spirit never dies
+++++++++++++

You could use this instead of an external air brick.

JohnD · 28 Aug 2010

if you have floorboards downstairs, and if the sub-floor is ventilated with airbricks to keep it dry, there will usually be plenty of draughts to feed the fire. Equally if you have modern windows with open trickle vents. How old is the house?

If you need an airbrick or similar for the fire, it can be next to the fireplace to prevent draughts through the room. In very posh houses you sometimes get a brass grill set into the floor in front of the fireplace to let air in. This can go the ventilated subfloor or cellar if you have one, or to a duct that goes out through the wall. If it sucks air from the cellar or subfloor, it is keeping the ventilation going which keeps it drier, and any damp air goes straight up the chimney.

btw if you are digging round the house for a new path, this is a good time to put in any extra airbricks for the cellar or subfloor, or at least clear the rubble, dirt and cobwebs out of the old ones.

karaman · 30 Aug 2010

hallo johnD,

ground floor only, no cellar, concrete floors, no fireplace, just a hole in the chimney-stack for the stove, thats why i think there will be no movement of air so condensation will settle on the walls.

the vent in the door is a new one on me but seems an easier solution than holes in the brick.

there is existing 20" path around house, the sloping concrete will be over this. work will begin when break in weather is expected.

thanks

karaman

JohnD · 30 Aug 2010

is there a damp-course in the walls?

karaman · 31 Aug 2010

hallo johnd,

no dpc - having waited for six weeks, i got let down badly by both individuals who gave me a quote. so no dpc so im gonna set about plastering the walls myself. joy!

cheers

karaman

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concrete mixture to stop water draining into foundations?

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