Sealing brickwork between adjoining extensions

16 Jul 2006
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United Kingdom
Neighbours have just built a rear ground floor extension which adjoins our own similar extension. (Traditional semi-det).

Theirs extends out a couple of feet more than ours, but there doesn't appear to be any sort of mortar or sealant where their new brickwork butts up against ours at the party line. Should their builder have sealed the tiny gap between the two sets of bricks? If so, should it be visible and obvious?

Although the gap is sheltered to some degree by the overhang of guttering above it and partly by the party fence panel, we are wondering if we need to be concerned about driving rain being drawn into the gap and causing damp problems to both extensions.

Comments and advice welcomed, please. Thanks.

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You have no problems to worry about, the gap will ensure a flow of air which will keep the brickwork in the void dry, much the same as a cavity.

What may be a worse problem is insects, and wasp's nests come to mind, I'm surprised the builders did not close the gap off during the construction works, would be worthwhile having a chat with your neighbours as they would be just as badly affected as yourselves, and it would be worthwhile closing off the gap/s.

If these walls are so close together, then how have the roofs been finished at the boundary?

TBH, insects are not on the look out for a gap between two walls - there are hundreds of other places for them
Thanks for your time, appreciated.

Perhaps I did not describe "the gap" well enough. Their bricks are butted up hard against ours - so the gap is only a millimeter or three maybe where the two sets of brick surfaces don't always quite touch, especially at pointing runs.

Their new pitched roof tiles have been matched and linked into ours (which are only a year old anyway) and appear to give a continous cover across both extensions. The same pitch to ours has been maintained at roof level. I don't know what went on under the tiles, though - I presume the felts would have been overlapped somehow.

Concern was whether driving rain might be drawn by capillary action into that tiny gap at the right angle where both sets of brickwork meet, i.e. from gutter level down to ground level. Could that happen and should it normally be sealed to prevent it affecting both properties?
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The gap is not an issue, and nothing to worry about.

However, from a quality point of view, the joint should have been formed with some 12mm fibre board fill material and then sealed continuously with polysulphide mastic

As it is, gouge the joint out a bit and run some silicone or polysulphide mastic up the joint. Coloured to match the bricks or clear
Thanks to alittlerespect and woody for taking time to reply. Much appreciated. Comments are very helpful - as always. :D

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