damp proofing an external porch

[Ian & Hilda Dedic]

I have an open external porch on my house, which was added in about

1985. it consists of a breeze block waist high wall on either side with wooden supports to a tiled porch section.

The previous owner, in his wisdom neglected to put a damp proof membrane in the breeze block 1 block above ground level so that the porch work bridges the damp proof course of the main house.

So recently I was annoyed to discover that the internal plaster by the bottom of the front door had blown somewhat (When the hoover bashed into it and a huge chunk of plaster crumbled away).

I need to fix this and wondered if I could effectively do a drill and inject chemical damp proofing as a diy thing or if I would be better off getting a proper company to do it for me, I don't want the whole house doing, just the bit in the porch. I suspect a dpc company wouldn't want to do such a small job and would try to talk me into having the whole front of the house done.

I don't really want knock down the porch and start again because I quite like it as it is (apart from this damp problem).

Opinions please.

Angle grinder at the ready....

dedics

[Jim K]

indeed unless it's a big one rent a 12" one and cut through the blocks as near to the house wall as you can, then insert some plastic DPC (on a roll) say 4" wide? into the vertical slot - thus isolating the porch blocks from your house wall. It won't be necessary to cut all the way to the top - just the bottom

18" say (measured from your house DPC)

Alternatively there are assorted siloxane damp injection "creams" - Sovereign do one - that you could try but I've never used em so can;t comment... others doubtless will ;>)

Jim K

[Ian & Hilda Dedic]

On 10/09/2010 11:54, Jim K wrote:>>

Great idea, but the porch paint flakes off due to damp from the bottom all the way round the breeze blocks, I've just assumed in the past it was water splashback from rain that had caused the damage and removed and repainted every couple of years, but it might be rising damp from under the slab. So I'd prefer to get all the breeze block porch bit damp proofed if economical.

Why he didn't put a dpc under the concrete for the doorstep slab when he was building it I don't know.

dedics

[Dave Liquorice]

Presumably these dwarf walls are not tied into the house brickwork either? Why not cut out the mortar between the blocks and the bricks and insert a bit of DPM gap against the bricks (full thickness of the blocks of course...) and remortar.

Neater, IMHO, than angle grinding right through the blocks some distance from the wall as with thatyou'd still have a thin sliver of block bridging the house DPM unless you hacked it out then you have a big gap to fill...

[Jim K]

rent the damp proofing pump etc from HSS and do it yourself exactly how you want it?

Jim K