Extension wall cavity is wet under window (Ed.)

[emilyjane]

Hi, new here but hoping someone can help. Opened up the cavity on one side of our conservatory door to inspect some bad damp that we had there. Pulled out all the old fibreglass insulation which was soaked through and home to an ants nest, but now I need to decide whether to insulate again or keep the cavity open, and how to install a cavity closer with the door in place. The cavity also isn't one width all the way up so it would be tricky to cut the cavity closer to size to get a good fit. It was previously just plasterboard and plaster.
We've determined that the eroded mortar to the exterior is most likely the cause of the damp, and I will be repointing before sealing the cavity back up to make sure the issue is resolved.
Please see photos below:

Open cavity.

Ext. view.

Damage to mortar towards top of wall just below window sill.

Gap formed between conservatory brickwork and garage. Clearly wasn't tied in properly when the conservatory was added. Do I retrofit wall ties or just repair the mortar??

My cat wondering why on Earth I'm dragging fluff out of the walls. I've clearly gone mad and he looks concerned about it.

Thank you in advance for any help!

 

[JohnD]

The brickwork below the window looks decidedly wet. Where is the frame draining to?

Loft insulation can get wet, but the fibreglass CWI in my house is treated, I think with silicone wax, and repels water, you can't wet it. I think yours has the wrong stuff

You could perhaps poke closed-cell foam board into the gap instead, but you need first to work out where the water is coming from and correct it.

Look into the cavity with a torch while someone sprays a hose onto the wall, the cill, the sides, the head of the frame, and then above the window and on the gutter and roof. They must start at the bottom, or it will run down the outside and you won't know where it's getting in. You can also use a selfie stick to look in the caviy.

 

[noseall]

Hi, new here but hoping someone can help. Opened up the cavity on one side of our conservatory door to inspect some bad damp that we had there. Pulled out all the old fibreglass insulation which was soaked through and home to an ants nest, but now I need to decide whether to insulate again or keep the cavity open, and how to install a cavity closer with the door in place. The cavity also isn't one width all the way up so it would be tricky to cut the cavity closer to size to get a good fit. It was previously just plasterboard and plaster.
We've determined that the eroded mortar to the exterior is most likely the cause of the damp, and I will be repointing before sealing the cavity back up to make sure the issue is resolved.
Please see photos below:

View attachment 361005
Open cavity.

View attachment 361004
Ext. view.

View attachment 361003
Damage to mortar towards top of wall just below window sill.

View attachment 361006
Gap formed between conservatory brickwork and garage. Clearly wasn't tied in properly when the conservatory was added. Do I retrofit wall ties or just repair the mortar??

View attachment 361007
My cat wondering why on Earth I'm dragging fluff out of the walls. I've clearly gone mad and he looks concerned about it.

Thank you in advance for any help!

It's your typical poorly built connie. The foundations are probably just beneath the grass too and don't seem to be adequate, looking at that brick panel.
Up to you whether you take the inner leaf or the outer leaf down and re-build with say Dritherm cav batts etc and correct (cavity closer) masonry jambs. Were knocking down lots of connies these days and building proper extensions in their place.

 

[emilyjane]

It's your typical poorly built connie. The foundations are probably just beneath the grass too and don't seem to be adequate, looking at that brick panel.
Up to you whether you take the inner leaf or the outer leaf down and re-build with say Dritherm cav batts etc and correct (cavity closer) masonry jambs. Were knocking down lots of connies these days and building proper extensions in their place.

Thank you, it's clearly poorly built. Luckily it's only that one spot that we get any damp but it's still not great!! I think rebuilding would be more money and time than it's worth, and we've just replaced the roof on the damn thing. The cavity also ends at floor level as they've poured the concrete floor into the cavity as well. I'm looking for the easiest fix that I can do myself to prevent the damp without it costing the earth. To rebuild the inner leaf and add a proper cavity closer/jamb would the door need to be removed?

 

[^woody^]

To me, it looks like the dampness follows that crack in the mortar and that vertical joint. Seal the cracks and see what happens.

Slide some DPC into the reveal and then close the cavity with some expanding foam.

If the rest of the cavity is insulated, then yes put insulation back in. When that damp fibreglass dries out, you can use that.

 

[emilyjane]

To me, it looks like the dampness follows that crack in the mortar and that vertical joint. Seal the cracks and see what happens.

Slide some DPC into the reveal and then close the cavity with some expanding foam.

If the rest of the cavity is insulated, then yes put insulation back in. When that damp fibreglass dries out, you can use that.

Yes, it definitely looks like the cracked mortar is to blame, I'll be sorting that this week. I'll probably replace the insulation since it's full of soil and ants as there was a nest in there, yuck! Thanks for the advice!

 

[noseall]

The cavity also ends at floor level as they've poured the concrete floor into the cavity as well ‍

What they actually do, is worse than that.
They dig a very narrow (spade width) foundation, for the outer course of brickwork only.
They build the outer course brickwork up to DPC, then fill in the over-site and pour the slab.
They then build the inner leaf off the slab.

Very low end stuff. Most of the budget goes towards the UPVC.

 

[emilyjane]

What they actually do, is worse than that.
They dig a very narrow (spade width) foundation, for the outer course of brickwork only.
They build the outer course brickwork up to DPC, then fill in the over-site and pour the slab.
They then build the inner leaf off the slab.

Very low end stuff. Most of the budget goes towards the UPVC.

I thought that was the case but was trying to give some credit and not assume the worst, there's a lot of bad work on this house that we're slowly undoing... Fortunately I think the conservatory has the worst of it! We've replaced the plastic roof with glazing which has made a huge improvement, now to tackle the damp before we replace the green laminate tiles with limestone! Thanks again for commenting

 

[JohnD]

Yes, it definitely looks like the cracked mortar is to blame, I'll be sorting that this week. I'll probably replace the insulation since it's full of soil and ants as there was a nest in there, yuck! Thanks for the advice!

If you can lay your hands on a builders canister vac, you can push the tube into the cavity and it can suck up soil, sand, mortar snots, pieces of broken brick, and some can suck up water or wet mud. They are available at places like Screwfix, and sometimes at Aldi or Lidl.

Don't use a domestic vacuum, which is less powerful and easily damaged by the abrasive grit and dust

 

[emilyjane]

If you can lay your hands on a builders canister vac, you can push the tube into the cavity and it can suck up soil, sand, mortar snots, pieces of broken brick, and some can suck up water or wet mud. They are available at places like Screwfix, and sometimes at Aldi or Lidl.

Don't use a domestic vacuum, which is less powerful and easily damaged by the abrasive grit and dust

Already done this with our Draper wet vac, but thanks! It's good advice for anyone else who might have the same issue as us. Edit: although I would say that compared to our domestic Miele, the Draper has no where near the suction power. I'm tempted to wait until the cavity has dried out and then go back in with the Miele to get any remaining sediment.

 

[JohnD]

That's odd. I have a similar one, and a Miele.

Is your Draper filter clogged?

 

[emilyjane]

That's odd. I have a similar one, and a Miele.

Is your Draper filter clogged?

Clean the filters after each use, and it's only a few months old. I think our Miele is just so good that the Draper is weak in comparison.

 

[emilyjane]

The brickwork below the window looks decidedly wet. Where is the frame draining to?

Loft insulation can get wet, but the fibreglass CWI in my house is treated, I think with silicone wax, and repels water, you can't wet it. I think yours has the wrong stuff

You could perhaps poke closed-cell foam board into the gap instead, but you need first to work out where the water is coming from and correct it.

Look into the cavity with a torch while someone sprays a hose onto the wall, the cill, the sides, the head of the frame, and then above the window and on the gutter and roof. They must start at the bottom, or it will run down the outside and you won't know where it's getting in. You can also use a selfie stick to look in the caviy.

Thanks for the idea with the hose. Would be a good way to see where the water is coming from. I'll replace the old insulation with the proper stuff.