Jump to content
Sign in to follow this  
paul1966

sealant for between concrete roof and brick wall

Recommended Posts

we have a flat conrete roof that butts up against a brick wall. where the join is there is lead flashing but we are having a bit of water leak in through the gap where the wall meets the slab. I think its rain thats pooling on the slab and seeping under the flashing. With advances in modern technology i am wondering if there is a sealant i could use to seal the gap outside  and maybe do away with the flashing? Anyone know of any?

Share this post


Link to post
Share on other sites

I would also say that the lead used in this way gets tired over the years and may need replacing. Long time since I have dressed any lead.

If you can gently lift the lead on a fine day. Add a bead of Leadmate in to the gap. Leave it a little proud and re-dress the lead carefully back down over the wet sealant.

Good luck

Edited by TIGHTCHOKE
SPELLAGE!

Share this post


Link to post
Share on other sites
Just now, Lord Geordie said:

People used to laugh at me when I used good old fashioned car under seal. 

It will work but is a rather messy way to get the same result.

Share this post


Link to post
Share on other sites

I used to use a sealant gun and pipe it thick in two lines then press down enough to form the lead flat. Worked a treat and never made a mess! 

Share this post


Link to post
Share on other sites

I'm sorry, but a lead flashing on a flat concrete roof abutment is basically useless, unless,,,,,

The concrete is cast into the wall with an upstand.

If it is plain concrete flush with the brickwork, supported by a beam beneath, then there is a separation occurring allowing the ingress of rainwater.

A suitable sealant would solve the leak short term. Long term it may need further investigation. Sounds like a design fault to me.

Possible to post up pictures of the offending area ?

Share this post


Link to post
Share on other sites

i have not had a look under the flashing yet, I think that will be a job for the summer. There is a concrete beam supporting the rear wall and the concrete slab butts that so i would not be surprised if its like you say. The house was built in the 1950's. Its only a small leak and only when it tips it down so i am hoping sealant will fix it if i put plenty on.

Share this post


Link to post
Share on other sites
6 minutes ago, paul1966 said:

i have not had a look under the flashing yet, I think that will be a job for the summer. There is a concrete beam supporting the rear wall and the concrete slab butts that so i would not be surprised if its like you say. The house was built in the 1950's. Its only a small leak and only when it tips it down so i am hoping sealant will fix it if i put plenty on.

From what you say, would the wind direction be part of the probelm?

Have seen this before where it only ever gets in if the wind is in an unusual direction combined with heavy rain.

Share this post


Link to post
Share on other sites

yes i am sure the wind direction does make a difference.

especially over the past couple of days due to the storm.

Edited by paul1966

Share this post


Link to post
Share on other sites

I've done a couple of quick sketches to show what I think you're describing, and how it should be. Either make sense to you? 

Just trying to help as much as possible 👍

IMG_20200216_115415.jpg

Share this post


Link to post
Share on other sites

Buy some torch on felt,easy enough to do you can make a felt upstand and leave the lead in place.

Share this post


Link to post
Share on other sites

yes i understand what you mean now, i am sure that it will be the first sketch that you have drawn will be the situation i have.  This is a picture from inside, the slab is on the left hand side and the crack is where the slab meets the concrete beam. Its a mess as we are renovating the kitchen, hence i want to fix the leak before re plastering.

 

 

20200216_121324.jpg.77c1429adaedb7218685ee7f8f1e96af.jpg

11 minutes ago, B725 said:

Buy some torch on felt,easy enough to do you can make a felt upstand and leave the lead in place.

Funnily next doors had there slab completely covered with felt before they rented it out and they have just had someone out with a sealant gun re sealing along the join so it looks like they are having the same problem.

Share this post


Link to post
Share on other sites

A roll of flash band is what I would use. Fold the lead flashing back and flash band under it up the wall where water is getting in. Warm with blow lamp and rub with a rag to make it stick. Fold lead back over it. Not getting weathered it should last decades.

Share this post


Link to post
Share on other sites

Judging by your picture, the ceiling spans across the beam?

If yes, then above that hole are the timber joists for an upstairs room?

And you're right, it's a mess! Just watch out for ACM's.... 

Asbestos Containing Materials.

Lots to list, do a Google search if you're unsure 😉

Share this post


Link to post
Share on other sites

I have took some more pics from outside, you are right about the joists. I think until i lift up the flashing i won't know for sure but could the slab just butt up against the wall like in my sketch?

20200216_131427.jpg

20200216_131607.jpg

20200216_132225.jpg

Share this post


Link to post
Share on other sites

Put a liquid fiberglass covering over crete,at junction of wall put 45* bevel cut 2x2 batten fibre mesh and glass over to form lip and your existing counter flashing will dress down,,roof sealed and easy DIY task,if your up for that kinda thing 

Share this post


Link to post
Share on other sites

I have used frame sealant in the past. 
anything that sits flush maybe difficult to seal permanently. 
you could also plumbers mait - I have used this to great effect on leaking gutters and sheds. 

Share this post


Link to post
Share on other sites

The felt has only been put down flat with no upstand, easy fix with torch on felt if your ok using a blow lamp

Share this post


Link to post
Share on other sites
1 minute ago, B725 said:

The felt has only been put down flat with no upstand, easy fix with torch on felt if your ok using a blow lamp

just to be clear thats lead flashing thats on the roof not felt, but i do think water is getting under where it sits flat on the roof.

Share this post


Link to post
Share on other sites

The water will wick up to the back edge of the felt, by making an upstand under the flashing and sealed onto the flat roof will eliminate the joint. .picture two show's were the mineral felt just butts up to the brick work with no visible upstand. To use torch on felt your actually melt the bitchum on the back of the felt then fit it by rolling if it's a flat area or gently pressing if doing by hand. The felt is around 4mm thick and stick to any dry surface. Both my car port and flat concrete roof are done this way with the felt upstand under the flashing

Share this post


Link to post
Share on other sites
1 hour ago, paul1966 said:

I have took some more pics from outside, you are right about the joists. I think until i lift up the flashing i won't know for sure but could the slab just butt up against the wall like in my sketch?

20200216_131427.jpg

20200216_131607.jpg

20200216_132225.jpg

 

In the first picture is that an asphalt layer over the concrete slab? Can't really make it out as it is wet. Can't see concrete 'sagging' like that. That big hole/sunken area looks worrying. There is lead flashing and I'm sure there is 'flashband' beneath that from a previous attempt to seal it.

I'm sure that the slab would have been cast beneath that external brickwork.

Whatever the make up, that needs some attention ASAP!

Share this post


Link to post
Share on other sites

its just a bare concrete slab, its darker due to the rain, the dip in the picture is just a shallow pool of rain water not a sunken area. i have been up on the slab and its in good order, its just the lead flashing that needs looking at, you are correct it has been repaired before. I think i need to lift the flashing up and see whats underneath if anything.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...